Novatel Softwareversion445om20000026rev1 User Manual 8504cdf9 F3a1 4ac5 A7e0 B746cbae8f0c
User Manual: novatel softwareversion445om20000026rev1 Novatel Marine GPS System Software Version 4.45 OM-20000026 Rev 1 User Guide |
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Software Version 4.45 OM-20000026 Rev 1 MiLLennium GPSCard TM Command Descriptions Manual GPSCard™ Products NovAtel Inc. Table of Contents TABLE OF CONTENTS TABLE OF CONTENTS 1 Quick Start 1.1 Installation .............................................................................................................................................................. 1 Graphical Interface ......................................................................................................................................... 1 1.2 Data Logging .......................................................................................................................................................... 2 1.3 Differential Operation ............................................................................................................................................ 3 Establish a Data Link ..................................................................................................................................... 3 Initialization - Reference Station ................................................................................................................... 4 1.4 RTK Mode ........................................................................................................................................................... 5 Data Communications Link ........................................................................................................................... 5 System Initialization ...................................................................................................................................... 6 Monitoring Your RTK Output Data ............................................................................................................... 7 Options For Logging Differential Corrections ............................................................................................... 7 Initialization - Rover Station .......................................................................................................................... 9 2 Command Descriptions 2.1 General ................................................................................................................................................................... 10 2.2 Command Tables .................................................................................................................................................... 11 All Commands: .............................................................................................................................................. 16 3 Special Data Input Commands 3.1 Almanac Data ......................................................................................................................................................... 17 $ALMA.. ......................................................................................................................................................... 18 $IONA............................................................................................................................................................. 18 $UTCA............................................................................................................................................................ 19 3.2 Differential Corrections Data ................................................................................................................................. 19 $PVAA/B ........................................................................................................................................................ 19 $REPA/B......................................................................................................................................................... 19 $RTCA ............................................................................................................................................................ 20 $RTCM ........................................................................................................................................................... 20 $TM1A/B ........................................................................................................................................................ 21 4 Data Logs 4.1 Output Logging ...................................................................................................................................................... 22 4.2 NovAtel Format Data Logs .................................................................................................................................... 23 General ........................................................................................................................................................... 23 ASCII Log Structure ...................................................................................................................................... 23 Binary Log Structure ...................................................................................................................................... 23 4.3 RTK ........................................................................................................................................................................ 24 4.4 NMEA Format Data Logs ...................................................................................................................................... 25 General ........................................................................................................................................................... 25 4.5 GPS Time vs Local Receiver Time ........................................................................................................................ 26 4.6 Log Tables .............................................................................................................................................................. 26 5 Special Pass-Through Logs 5.1 Command Syntax ................................................................................................................................................... 31 5.2 ASCII Log Structure .............................................................................................................................................. 32 5.3 Binary Log Structure ............................................................................................................................................... 33 6 Message Formats 6.1 RTCA-Format Messages ........................................................................................................................................ 34 RTCA Standard Logs ..................................................................................................................................... 35 6.2 RTCM-Format Messages ....................................................................................................................................... 36 RTCM Standard Commands and Logs .......................................................................................................... 37 RTCM General Message Format ................................................................................................................... 38 RTCM Standard Commands .......................................................................................................................... 38 RTCM Standard Logs .................................................................................................................................... 39 MiLLennium Command Descriptions Manual iii Table of Contents 7 RINEX-Standard Commands & Logs 7.1 Commands .............................................................................................................................................................. 46 7.2 Logs ........................................................................................................................................................................ 47 RINEX ............................................................................................................................................................ 47 XKIN............................................................................................................................................................... 47 XNAV ............................................................................................................................................................. 47 XNHD ............................................................................................................................................................. 48 XOBS .............................................................................................................................................................. 48 XOHD ............................................................................................................................................................. 48 XSTA .............................................................................................................................................................. 49 APPENDICES A GPS Overview A.1 GPS System Design ............................................................................................................................................... 50 The Space Segment ........................................................................................................................................ 51 The Control Segment ..................................................................................................................................... 51 The User Segment .......................................................................................................................................... 51 A.2 Height Relationships ............................................................................................................................................. 51 A.3 GPS Positioning .................................................................................................................................................... 52 Single-Point vs. Relative Positioning ............................................................................................................. 53 Static vs. Kinematic Positioning .................................................................................................................... 54 Real-time vs. Post-Mission Data Processing ................................................................................................. 54 A.3.1 Differential Positioning ...................................................................................................................................... 54 A.3.2 Pseudorange Algorithms .................................................................................................................................... 55 Pseudorange Differential Positioning ............................................................................................................ 55 Dual Station Differential Positioning ............................................................................................................. 58 A.4 Carrier-Phase Algorithms ...................................................................................................................................... 59 B Multipath Elimination Technology B.1 Multipath ............................................................................................................................................................... 61 Why Does Multipath Occur? ......................................................................................................................... 61 Consequences Of Multipath Reception .......................................................................................................... 62 B.2 Hardware Solutions For Multipath Reduction ....................................................................................................... 62 Antenna Site Selection ................................................................................................................................... 62 Antenna Designs ............................................................................................................................................ 63 Antenna Ground Planes ................................................................................................................................. 64 NovAtel’s Internal Receiver Solutions for Multipath Reduction .................................................................. 65 C Commands Summary ACCEPT ........................................................................................................................................................ 66 ANTENNAPOWER ...................................................................................................................................... 68 ASSIGN ......................................................................................................................................................... 69 CLOCKADJUST ........................................................................................................................................... 70 COMn ............................................................................................................................................................. 71 COMn_DTR ................................................................................................................................................... 71 COMn_RTS ................................................................................................................................................... 72 CONFIG ......................................................................................................................................................... 73 CRESET ......................................................................................................................................................... 74 CSMOOTH .................................................................................................................................................... 75 DATUM ......................................................................................................................................................... 76 DGPSTIMEOUT ........................................................................................................................................... 77 DIFF_PROTOCOL ......................................................................................................................................... 78 DYNAMICS .................................................................................................................................................. 79 ECUTOFF ...................................................................................................................................................... 80 EXTERNALCLOCK ..................................................................................................................................... 81 EXTERNALCLOCK FREQUENCY ............................................................................................................. 83 FIX HEIGHT ................................................................................................................................................. 84 FIX POSITION ............................................................................................................................................... 85 FIX VELOCITY ............................................................................................................................................ 86 FREQUENCY_OUT ..................................................................................................................................... 87 FRESET ......................................................................................................................................................... 88 HELP .............................................................................................................................................................. 89 iv MiLLennium Command Descriptions Manual Table of Contents LOCKOUT ..................................................................................................................................................... 90 LOG ............................................................................................................................................................... 91 MAGVAR ...................................................................................................................................................... 92 MESSAGES ................................................................................................................................................... 93 POSAVE ........................................................................................................................................................ 94 RESET ........................................................................................................................................................... 95 RESETHEALTH ........................................................................................................................................... 96 RESETHEALTHALL .................................................................................................................................... 96 RINEX ........................................................................................................................................................... 97 RTCM16T ...................................................................................................................................................... 98 RTCMRULE .................................................................................................................................................. 99 RTKMODE .................................................................................................................................................... 100 SAVEALMA ................................................................................................................................................. 104 SAVECONFIG .............................................................................................................................................. 105 SEND ............................................................................................................................................................. 106 SENDHEX ..................................................................................................................................................... 107 SETDGPSID .................................................................................................................................................. 108 SETHEALTH ................................................................................................................................................. 109 SETL1OFFSET .............................................................................................................................................. 110 SETNAV ........................................................................................................................................................ 111 SETTIMESYNC ............................................................................................................................................ 113 UNASSIGN ................................................................................................................................................... 114 UNASSIGNALL ............................................................................................................................................ 114 UNDULATION ............................................................................................................................................. 115 UNFIX ........................................................................................................................................................... 116 UNLOCKOUT ............................................................................................................................................... 116 UNLOCKOUTALL ....................................................................................................................................... 116 UNLOG .......................................................................................................................................................... 117 UNLOGALL .................................................................................................................................................. 117 USERDATUM ............................................................................................................................................... 118 VERSION ...................................................................................................................................................... 119 D Logs Summary Log Descriptions .......................................................................................................................................................... 120 ALMA/B ......................................................................................................................................................... 120 BSLA/B........................................................................................................................................................... 125 CDSA/B .......................................................................................................................................................... 128 CLKA/B ......................................................................................................................................................... 131 CLMA/B ......................................................................................................................................................... 133 COM1A/B and COM2A/B ............................................................................................................................ 135 DOPA/B ......................................................................................................................................................... 136 ETSA/B ........................................................................................................................................................... 138 FRMA/B.......................................................................................................................................................... 140 GGAB ............................................................................................................................................................. 141 GPALM .......................................................................................................................................................... 142 GPGGA ........................................................................................................................................................... 143 GPGLL............................................................................................................................................................ 144 GPGRS............................................................................................................................................................ 145 GPGSA............................................................................................................................................................ 146 GPGST ............................................................................................................................................................ 147 GPGSV............................................................................................................................................................ 148 GPRMB........................................................................................................................................................... 149 GPRMC........................................................................................................................................................... 150 GPVTG ........................................................................................................................................................... 151 GPZDA ........................................................................................................................................................... 152 GPZTG............................................................................................................................................................ 153 MKPA/B ......................................................................................................................................................... 154 MKTA/B ......................................................................................................................................................... 155 NAVA/B ......................................................................................................................................................... 156 PAVA/B .......................................................................................................................................................... 159 POSA/B........................................................................................................................................................... 161 PRTKA/B........................................................................................................................................................ 162 PVAA/B .......................................................................................................................................................... 164 PXYA/B .......................................................................................................................................................... 166 RALA/B .......................................................................................................................................................... 169 RASA/B .......................................................................................................................................................... 170 MiLLennium Command Descriptions Manual v Table of Contents RBTA/B .......................................................................................................................................................... 172 RCCA.............................................................................................................................................................. 173 RCSA/B .......................................................................................................................................................... 174 REPA/B........................................................................................................................................................... 175 RGEA/B/D ...................................................................................................................................................... 176 RINEX ............................................................................................................................................................ 185 RPSA/B ........................................................................................................................................................... 186 RTCA .............................................................................................................................................................. 187 RTCM ............................................................................................................................................................. 187 RTKA/B .......................................................................................................................................................... 188 RTKOA/B ....................................................................................................................................................... 190 RVSA/B .......................................................................................................................................................... 193 SATA/B .......................................................................................................................................................... 195 SPHA/B........................................................................................................................................................... 198 SVDA/B .......................................................................................................................................................... 199 TM1A/B .......................................................................................................................................................... 201 VERA/B .......................................................................................................................................................... 202 VLHA/B.......................................................................................................................................................... 203 WRCA/B ......................................................................................................................................................... 205 E Comparison Of RT-2 And RT-20 E.1 RT-2 & RT-20 Performance .................................................................................................................................. 206 RT-2 Performance .......................................................................................................................................... 207 RT-20 Performance ........................................................................................................................................ 209 E.2 Performance Considerations .................................................................................................................................. 212 Performance Degradation .............................................................................................................................. 212 F Standards and References G Geodetic Datums H Some Common Unit Conversions I Information Messages Type 1 Information Messages ...................................................................................................................................... 219 !ERRA ............................................................................................................................................................ 219 !MSGA ........................................................................................................................................................... 219 Type 2 Information Messages ...................................................................................................................................... 220 J Listing Of Tables K GPS Glossary of Terms L GPS Glossary of Acronyms vi MiLLennium Command Descriptions Manual Table of Contents FIGURES 5-1 A-1 A-2 A-3 A-4 A-5 A-6 B-1 B-2 B-3 B-4 C-1 C-2 C-3 C-4 C-5 C-6 D-1 D-2 E-1 E-2 E-3 E-4 E-5 E-6 E-7 E-8 Pass-Through Log Data ................................................................................................................................................... 31 NAVSTAR Satellite Orbit Arrangement ......................................................................................................................... 50 Illustration of GPSCard Height Measurements ................................................................................................................ 52 Accuracy vs. Precision ..................................................................................................................................................... 53 Example of Differential Positioning ................................................................................................................................ 54 Single Point Averaging .................................................................................................................................................... 57 Typical Differential Configuration ................................................................................................................................... 58 Illustration of GPS Signal Multipath ................................................................................................................................ 61 Illustration of GPS Signal Multipath vs. Increased Antenna Height ............................................................................... 63 Illustration of Quadrifilar vs. Microstrip Patch Antennae ................................................................................................ 64 Example of GPSAntenna on a Flat Plate vs. Choke Ring Ground Plane ......................................................................... 64 HELP Command Screen Display ..................................................................................................................................... 89 Appended Command Screen Display ............................................................................................................................... 89 Illustration of Magnetic Variation & Correction .............................................................................................................. 92 Using SEND Command ................................................................................................................................................... 106 Illustration of SETNAV Parameters ................................................................................................................................. 112 Illustration of Undulation ................................................................................................................................................. 115 Example of Navigation Parameters .................................................................................................................................. 158 The WGS84 ECEF Coordinate System ........................................................................................................................... 168 Typical RT-2 Horizontal Convergence - Static Mode ...................................................................................................... 208 Typical RT-2 Horizontal Convergence - Kinematic Mode ....................................................................... ....................... 208 RT-2 Accuracy Convergence ........................................................................................................................................... 209 Illustration of RT-2 Steady State Performance ................................................................................................................. 209 Typical RT-20 Convergence - Static Mode .................................................................................... .................................. 210 Typical RT-20 Convergence - Kinematic Mode .............................................................................................................. 211 RT-20 Steady State Performance ...................................................................................................................................... 211 RT-20 Re-Initialization Process ....................................................................................................................................... 213 TABLES 1-1 GPSCard Pseudorange Differential Initialization Summary ............................................................................................. 4 1-2 Latency-Induced Extrapolation Error ................................................................................................................................ 5 2-1 Commands By Function Table ......................................................................................................................................... 11 2-2 GPSCard Command Summary ......................................................................................................................................... 13 4-1 Logs By Function Table .................................................................................................................................................... 26 4-2 GPSCard Log Summary .................................................................................................................................................... 28 6-1 Positioning Modes ............................................................................................................................................................. 34 C-1 Antenna LNA Power Configuration ................................................................................................................................. 68 C-2 Default Values of Process Noise Elements ...................................................................................................................... 82 C-3 VARF Range .................................................................................................................................................................... 87 D-1 GPSCard Solution Status ................................................................................................................................................. 127 D-2 Position Type ................................................................................................................................................................... 127 D-3 RTK Status for Position Type 3 (RT-20) ......................................................................................................................... 127 D-4 RTK Status for Position Type 4 (RT-2) ........................................................................................................................... 127 D-5 Receiver Self-Test Status Codes ...................................................................................................................................... 180 D-6 Range Record Format (RGED only) ................................................................................................................................ 183 D-7 Channel Tracking Status .................................................................................................................................................. 184 D-8 Ambiguity Types .............................................................................................................................................................. 192 D-9 Searcher Status ................................................................................................................................................................. 192 D-10 RTK Status ........................................................................................................................................................................ 192 D-11 GPSCard Range Reject Codes ......................................................................................................................................... 196 D-12 GPSCard Velocity Status ................................................................................................................................................. 204 E-1 Comparison of RT-2 and RT-20 ....................................................................................................................................... 206 E-2 RTK Messages vs. Accuracy ............................................................................................................................................ 206 E-3 RT-2 Performance: Static Mode ....................................................................................................................................... 207 E-4 RT-2 Performance: Kinematic Mode ............................................................................................................................... 207 E-5 RT-20 Performance .......................................................................................................................................................... 210 G-1 Reference Ellipsoid Constants ......................................................................................................................................... 215 G-2 Transformation Parameters (Local Geodetic to WGS84) ................................................................................................ 215 I-1 Type 1 !ERRA Types ....................................................................................................................................................... 219 I-2 Type 1 !MSGA Types ...................................................................................................................................................... 220 For you convenience these tables, up to and including Appendix E, are also listed in Appendix J. MiLLennium Command Descriptions Manual vii 1 Quick Start 1 QUICK START 1 QUICK START This chapter is dedicated to getting you started. You may wish to carry out Real-Time Kinematic (RTK) positioning, operate in Differential modes or simply log data. Where to get further information is referenced after each of these sections. 1.1 INSTALLATION For more detailed instructions on the installation and set up of your GPSCard please see the accompanying MiLLennium GPSCard Guide to Installation and Operation. The MiLLennium receiver is an OEM product designed for flexibility of integration and configuration. You are free to select an appropriate data and signal interface, power supply system and mounting structure. This concept allows OEM purchasers to custom-design their own GPS-based positioning system around the OEM series GPSCard. Installing the MiLLennium GPSCard typically consists of the following: • Mounting the OEM series GPSCard in a secure enclosure to reduce environmental exposure, RF interference and vibration effects • Pre-wiring the I/O harness and the 64-pin DIN female connector for power and communications, then connecting them to the OEM series GPSCard • Installing the GPSAntenna, then connecting it to the OEM series GPSCard • (Optional) Installing an external oscillator OPERATION Once the hardware and software installations have been completed, you are now ready to begin initial operation of the GPSCard receiver. Communication with the MiLLennium GPSCard consists of issuing commands through the COM1 or COM2 port from an external serial communications device. This could be either a terminal or an IBM-compatible PC that is directly connected to a MiLLennium GPSCard COM port using a null modem cable. BOOT UP The initial operating software and firmware of the MiLLennium GPSCard resides in its read-only memory. As such, the unit “self-boots” upon power-up. The green LED indicator should blink about once per second if the unit is operating normally. The red one lights up if an error is detected during a self-test. The self-test status word can be viewed in the RGEA/B/D and RVSA/B data output logs. If a persistent error develops please contact the NovAtel GPS Customer Service Department for further assistance COMMUNICATION DEFAULT SETTINGS COM1 and COM2 for the MiLLennium GPSCards are defaulted to the following RS232 protocol: • 9600 bps, no parity, 8 data bits, 1stop bit, no handshake, echo off Graphical Interface If your GPSCard comes with a disk containing NovAtel’s graphical interface software GPSolution, a Microsoft Windows-based program, then you will be able to use your GPSCard without struggling with communications protocol or writing make-do software. The View menu options allow you to select or de-select various visual aids and display screens. Take a look at all of the options and keep open those you wish to display. To send commands and log data the Command Console screen should be visible. ASCII format logs can be monitored on the ASCII Record screen. MiLLennium Command Descriptions Manual 1 1 Quick Start e.g. On the command line of the Command Console screen type:log com1 posa once After you hit thekey the ASCII Record screen will display the output for your current position. See the POSA/B log description in Appendix D. 1.2 DATA LOGGING The GPSCard has four major logging formats: • NovAtel Format Data Logs (ASCII/Binary) • NMEA Standard Format Data Logs (ASCII) • RTCM Standard Format Data Logs (Binary) • RTCA Standard Format Data Logs (Binary) All data types can be logged using several methods of triggering each log event. Each log is initiated using the LOG command. The LOG command and syntax are listed on the following page. Syntax: Syntax LOG port datatype trigger period offset hold log [port],datatype,[trigger],[period],[offset],{hold} Description COM1 or COM2 Defaults to the port that the command was entered on. Enter one of the valid ASCII or Binary Data Logs (see Chapter 4 and Appendix D) Enter one of the following triggers. ONCE Immediately logs the selected data to the selected port once. Default if trigger field is left blank. ONMARK Logs the selected data when a MARKIN electrical event is detected. Outputs internal buffers at time of mark - does not extrapolate to mark time. Use MKBA/B for extrapolated position at time of mark. ONNEW Logs the selected data each time the data is new even if the data is unchanged. ONCHANGED Logs the selected data only when the data has changed. ONTIME Immediately logs the selected data and then periodically logs the selected data at a [period], [offset] frequency determined by the period and offset parameters. The logging will continue until an UNLOG command pertaining to the selected data item is received (see UNLOG Command). CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer associated with the chosen port becomes empty. The continuously option was designed for use with differential corrections over low bit rate data links. This will provide optimal record generation rates. The next record will not be generated until the last byte of the previous record is loaded into the output buffer of the UART. Use only with the ONTIME trigger. Units for this parameter are seconds. The selected period may be any value from 0.05 second to 3600 seconds. Selected data is logged immediately and then periodic logging of the data will start at the next even multiple of the period. If a period of 0.20 sec is chosen, then data will be logged when the receiver time is at the 0.20, 0.40, 0.60 and the next (0.80) second marks. If the period is 15 seconds, then the logger will log the data when the receiver time is at even 1/4 minute marks. The same rule applies even if the chosen period is not divisible into its next second or minute marks. If a period of 7 seconds is chosen, then the logger will log at the multiples of 7 seconds less than 60, that is, 7, 14, 21, 28, 35, 42, 49, 56 and every 7 seconds thereafter. Use only with the ONTIME trigger. Units for this parameter are seconds. It provides the ability to offset the logging events from the above startup rule. If you wished to log data at 1 second after every minute you would set the period to 60 seconds and the offset to 1 second (Default is 0). Will prevent a log from being removed when the UNLOGALL command is issued Example LOG COM1 POSA ONTIME 60 1 HOLD The syntax for a command can contain optional parameters (OPT1, OPT2, ...). OPT2 may only be used if it is preceded by OPT1. OPT3 may only be used if it is preceded by OPT2 and so on. Parameters after and including OPT1 will be surrounded by square brackets. An optional parameter such as {hold} surrounded by braces may be used with the log without any preceding optional parameters. Example: log com1 posa 60 1 hold log com1 posa hold 2 MiLLennium Command Descriptions Manual 1 Quick Start Example: log com1,posa,ontime,60,1 If the LOG syntax does not include a trigger type, it will be output only once following execution of the LOG command. If trigger type is specified in the LOG syntax, the log will continue to be output based on the trigger specification. Specific logs can be disabled using the UNLOG command, whereas all enabled logs will be disabled by using the UNLOGALL command (see Chapter 2 and Appendix C). All activated logs will be listed in the receiver configuration status log (RCCA). The [port] parameter is optional. If [port] is not specified, [port] is defaulted to the port that the command was received on. COMMONLY USED LOGS Type Logs Trigger Positioning PRTKA/B POSA/B ontime or onmark Post Processing RGEA/B/D REPA/B, ALMA/B ontime onchanged NMEA Position GPGLL GPGGA ontime or onmark Other useful logs are • • • • • RCCA to list the default command settings ETSA to monitor the channel tracking status SATA to observe the satellite specific data DOPA to monitor the dilution of precision of the current satellite constellation RVSA to monitor the receiver status For further information on output logging see Chapter 4 and the individual logs listed alphabetically in Appendix D. Use the HELP command to list all available commands. For more information on sending commands see Chapter 2 and the individual commands listed alphabetically in Appendix C. 1.3 DIFFERENTIAL OPERATION GPSCard receivers are capable of operating as either a reference station or a rover station. This makes the MiLLennium GPSCard ideal for design into DGPS systems. The GPSCard is capable of utilizing various formats of differential corrections. These formats are divided into two primary groups RTCM and RTCA. For detailed data structure concerning these logs, please see Chapters 4, 5, 6 and Appendix D. Establish a Data Link Operating the GPSCard with a DGPS system requires that the reference station broadcast differential correction data messages to one or more rover receivers. As there are many methods by which this can be achieved, it is up to you to establish an appropriate data link that best suits your user requirements. Whatever data link is chosen, the operator of the reference station will want to ensure that the bit rate of data transmission is suitable for the anticipated data link and remote users. Use the GPSCard COMn command to the COM port default bit rate (default is 9600 bps, no parity, 8 data bits, 1 stop bit, no handshake, echo off). Note that the GPSCard COMn_DTR and COMn_RTS commands are available for remote device keying (such as a radio transmitter). These commands allow for flexible control of the DTR and RTS lines to be precisely timed with log transmissions. MiLLennium Command Descriptions Manual 3 1 Quick Start Further information may be found in Appendix A. Table 1-1, following, is a GPSCard pseudorange differential initialization summary. Table 1-1 GPSCard Pseudorange Differential Initialization Summary REFERENCE MONITOR MONITORSTATION STATION REMOTE REM OTESTATION STATION Required: equired: FIX FIXPOSITION POSITIONlatlatlon lonhgt hgtidid(health) (health) LOG LOGport portDATATYPE ontime5 5 DATATYPEontime Required: Required: ACCEPT ACCEPTport portDATATYPE DATATYPE Recom ecom mm ended endedOptions: Options: (binary): LOG LOGDATATYPES DATATYPES(binary): RTCMB RTCMB RTCAB RTCAB RTCM RTCM RTCA RTCA Recom Recom mm ended endedOptions: Options: (binary): ACCEPT ACCEPT DATATYPES DATATYPES(binary): RTCM RTCM RTCA RTCA (ascii): LOG LOGDATATYPES DATATYPES(ascii): (ascii): ACCEPT ACCEPT COM COM M ANDS M ANDS(ascii): RTCMA RTCMA RTCAA RTCAA RTCMA RTCMA RTCAA RTCAA Related elated Com Com mm ands ands/Logs: /Logs: RTCMRULE RTCMRULE DATUM DATUM Related RelatedCom Com mm ands ands/Logs: /Logs: RTCMRULE RTCMRULE DATUM DATUM POSA/B POSA/B VLHA/B VLHA/B CDSA/B CDSA/B GPGGA GPGGA xam Exam ple ple1:1: fixfixposition position51.3455323 51.3455323-114.2895345 -114.28953451201.123 1201.123555 5550 0 loglogcom1 com1RTCM RTCMontime ontime2 2 Exam Exam ple ple1:1: accept acceptcom2 com2rtcm rtcm loglogcom1 com1posa posaontime ontime1 1 xam Exam ple ple2:2: fixfixposition position51.3455323 51.3455323-114.2895345 -114.28953451201.123 1201.123555 555 loglogcom2 com2rtcaa rtcaaontime ontime2 2 Exam Exam ple ple2:2: accept acceptcom2 com2commands comm ands loglogcom1 com1posa posaontime ontime0.2 0.2 loglogcom1 com1vlha vlhaontime ontime0.2 0.2 OTES: NOTES: Italicized Italicizedentries entriesindicate indicateuser userdefinable. definable. Initialization - Reference Station Differential mode of operation is established at the reference station through a two step process: fix position and logging observation and correction data. FIX POSITION The reference station must initialize the precise position of its reference antenna phase centre (lat/lon/hgt). This is accomplished by utilizing the GPSCard FIX POSITION command. The syntax is as follows: Syntax: FIX POSITION lat lon height station id health Example: fix position 51.3455323,-114.2895345,1201.123,555,0 4 MiLLennium Command Descriptions Manual 1 Quick Start NOTES: Entry of the station ID and health are optional The accuracy of the reference station’s FIX POSITION setting will directly affect the accuracy of its computed differential corrections. Good results at the rover station are dependent on the reference station’s combined position errors being kept to a minimum (e.g., fix position error + multipath errors). The GPSCard performs all computations based on WGS84 and is defaulted as such, regardless of DATUM command setting. The datum in which you choose to operate is converted from WGS84; therefore, all differential corrections are based on WGS84. Ensure that any change in your operating datum is set prior to FIX POSITION. When transmitting RTCM type data, the GPSCard has various options for assigning the number of data bits per byte. Please see the GPSCard command RTCMRULE, Appendix C for further information concerning RTCM data bit rule settings. The FIX POSITION “health” field entered will be reported in word 2 of the RTCM message frame header. Once the GPSCard has its position data fixed and is tracking three or more satellites, it is now ready to transmit differential correction and observation data to the rover stations. LOG BROADCAST DATA Assuming that a data link has been established, use the GPSCard log command to send observation and differential corrections data for broadcast to the rover stations. Syntax: LOG port data ontime seconds Example: log com1 rtcm ontime 5 REMINDER: Ensure that the bit rate of the data link is suitable for the differential type, logging rate and maximum message length of the data type being logged. 1.4 RTK MODE Currently, NovAtel’s RTK system uses proprietary messaging. Consequently, both the reference station and remote station must use NovAtel GPS receivers in order for the system to work and perform as described. Data Communications Link It is the user’s responsibility to provide a data communications link between the reference station and remote station. The data transfer rate must be high enough to ensure that sufficient reference station messages reach the remote station to keep extrapolation errors from growing too large; see Table 1-2. Table 1-2 Latency-Induced Extrapolation Error Time since last reference station observation Typical extrapolation error (CEP) 0-2 seconds 2-7 seconds 7-30 seconds 1 cm/sec 2 cm/sec 5 cm/sec Generally, a communications link capable of data throughput at a rate of 4800 bits per second or higher is sufficient. However, it is possible to satisfactorily use a lower rate; see Chapter 6, Message Formats for additional information. The minimum data transfer rate is based on the following: 1. RT-2 requires that the reference station periodically transmit two RTCA Standard Type 7 messages: MiLLennium Command Descriptions Manual 5 1 Quick Start 2. • An RTCAOBS message contains reference station satellite observation information, and should be sent once every 1 or 2 seconds. • An RTCAREF message contains reference station position information, and should be sent once every 10 seconds. RT-20 requires that the reference station periodically transmit either the RTCA messages listed above (the recommended option), or the RTCM SC-104 Type 3 & 59N messages: • A Type 3 message contains reference station position information, and should be sent once every 10 seconds (although it is possible to send it as infrequently as once every 30 seconds). • A Type 59N message contains reference station satellite observation information, and should be sent once every 2 seconds. Further information on RTCA and RTCM message formats is contained in Chapter 6. System Initialization The RTK system is designed for ease of use: you set up the remote station, enter a command so that it accepts RT2 or RT-20 messages from the reference station, and are ready to go. There are options, however, which can be used to adapt the system to a specific application. Some options apply only to the reference station, while others apply only to the remote station. Detailed descriptions can be found in Appendix C, Commands Summary. In the following sections, keep the following in mind: • Dynamics modes. For reliable performance the antenna should not move more than 1-2 cm when in static mode. See the RTKMODE commands in Chapter 2 and Appendix C for more information. • When using the FIX POSITION command, the height entered must be in metres above mean sea level; it will be converted to ellipsoidal height inside the receiver. You can enter an undulation value, if desired, using the UNDULATION command; if none is entered, the receiver estimates an undulation with its internal table. The format of the optional station ID field depends on whether RTCM or RTCA messages are being used: if RTCM, any number from 0 - 1023 is valid, while if RTCA, any 4-character string of numbers and upper-case letters, enclosed in quotation marks, is valid. See Appendix C for additional information on the station id field. • The COMn field refers to the serial port (either COM1 or COM2) to which data communications equipment is connected. The serial port assignment at the reference and remote stations need not be the same; e.g. a radio transmitter might be connected to COM1 at the reference station, and a radio receiver to COM2 at the remote station. INITIALIZATION FOR RTCA-FORMAT MESSAGING (RT-2 OR RT-20) The following commands will enable RTCA-format messaging and allow RT-2 or RT-20 to operate with the remote station either at rest or in motion. Note that the optional station health field in the existing FIX POSITION command is not currently implemented in NovAtel’s RTCA messages, though it will be in the future. 1. At the reference station: fix position lat,lon,height,station id log comn,rtcaref,ontime,interval log comn,rtcaobs,ontime,interval Example: fix position 51.11358042,-114.04358013,1059.4105,”RW34” 6 MiLLennium Command Descriptions Manual 1 Quick Start log com1,rtcaref,ontime,10 log com1,rtcaobs,ontime,2 2. At the remote station: accept comn,rtca Example: accept com2,rtca Congratulations! Your RTK system is now in operation! INITIALIZATION FOR RTCM-FORMAT MESSAGING (RT-20 ONLY) Although RT-20 can operate with either RTCA or RTCM-format messaging, the use of RTCA-format messages is recommended (see Chapter 6 for further information on this topic). Nevertheless, the following commands will enable RTCM-format messaging and allow RT-20 to operate with the remote station either at rest or in motion: 1. At the reference station: fix position lat,lon,height,station id,station health log comn,rtcm3,ontime,interval log comn,rtcm59,ontime,interval Example: fix position 51.11358042,-114.04358013,1059.4105,119,0 log com1,rtcm3,ontime,10 log com1,rtcm59,ontime,2 2. At the remote station: accept comn,rtcm Example: accept com2,rtcm Congratulations! Your RT-20 system is now in operation! Monitoring Your RTK Output Data At the remote station, you could now select any or all of these output logs for positioning information: • • • • • • BSLA/B Baseline Measurement NMEA-format logs POSA/B Computed Position PRTKA/B Best Position RPSA/B Reference Station Position & Health RTKOA/B RTK Output - Time Matched Positions The POSA/B, PRTKA/B and NMEA-format logs contain the low-latency position; the RTKA/B logs contain the matched position. The low-latency solution is the recommended one for kinematic users, while the matched solution is the one recommended for stationary users. For a discussion on low-latency and matched positions, see the Differential Positioning section of Appendix A. Options for Logging Differential Corrections SET DGPSTIMEOUT The DGPSTIMEOUT command allows the reference station to set the delay by which it will inhibit utilization of new ephemeris data in its differential corrections. This delay ensures that the remote receivers have had sufficient time MiLLennium Command Descriptions Manual 7 1 Quick Start to collect updated ephemeris data as well. A delay of 120 to 130 seconds will typically ensure that the rover stations have collected updated ephemeris. After the delay period is passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay value, you must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference station, DGPS delay will be ignored (see the DGPSTIMEOUT command found in Chapter 2 and Appendix C for further information on using this command at rover stations.) Syntax: DGPSTIMEOUT dgps delay Command ephem delay Option DGPSTIMEOUT Description Default Command dgps delay min. max. 2 1000 ephem delay min. max. 0 600 Maximum age in seconds 60 Minimum time delay in seconds 120 Example: dgpstimeout 2,300 USING RTCM SC-104 LOG TYPES RTCM SC-104 is a standard for transmitting differential corrections between equipment from different manufacturers. The NovAtel GPSCard is capable of transmitting or receiving RTCM data. To facilitate transmitting the RTCM data over shared data links, the GPSCard is also capable of sending the RTCM log in NovAtel ASCII format (RTCMA) or with the NovAtel Binary Header (RTCMB) added to allow synchronous transmission and reception along with other data types. REMEMBER: When sending or receiving RTCM log types, it is important to ensure that all connected equipment are using the same RTCMRULE for compatibility. The easiest method to send RTCM Standard logs is from the COM1 or COM2 ports of the reference GPSCard. The easiest method to receive the RTCM data is through the COM1 or COM2 port of the rover GPSCard. The rover GPSCard must issue the “ACCEPT port RTCM” command to dedicate a port before it will accept the RTCM data into that port. The RTCMA log can be intermixed with other NovAtel ASCII data over a common communication port. It will be directly interpreted by a rover GPSCard as a Special Data Input Command ($RTCM). “ACCEPT port COMMANDS” must be used with this input command. A non-NovAtel rover station will need to strip off the header ($RTCM) and terminator (*xx), then convert the hexadecimal data to binary before the RTCM Standard data can be retrieved. The RTCMB log can be intermixed with other NovAtel Binary data over a common communication port. REMEMBER: Use the CDSA/B logs to monitor the COM port activity, success, and decoding errors. USING RTCA LOG TYPES The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential Global Navigation Satellite System (DGNSS) Special Category 1 (SCAT-I) precision approaches. The perceived advantage to using RTCA type messages for transmitting and receiving differential corrections versus using RTCM type messages is that RTCM transmits 30-bit words, and the data is difficult to decode and process because of the parity algorithm and regular word sizes used. RTCA is transmitted in 8-bit words, which are easier 8 MiLLennium Command Descriptions Manual 1 Quick Start to generate, process and decode. The RTCA messages are therefore smaller, they have a 24 bit CRC that is much more robust than RTCM messages, and they permit the use of a four-alpha-character station ID. RTCA Standard logs can be received through the COM1 or COM2 port of the rover GPSCard. The remote GPSCard must issue the “ACCEPT port RTCA” command to dedicate a port before it will accept the RTCA data input to that port. The RTCA logs cannot be intermixed with other logs. The RTCAA log can be intermixed with other NovAtel ASCII data over a common communications port. It will be directly interpreted by a rover GPSCard as a Special Data Input Command ($RTCA). “ACCEPT port commands” must be used with this input command. A non-NovAtel rover station will need to strip off the header ($RTCA) and terminator (*xx), then convert the hexadecimal data to binary before the RTCA Standard can be retrieved. The RTCAB log can be intermixed with other NovAtel binary data. The COM1 or COM2 port of the remote GPSCard must be dedicated to receiving RTCA data only, and so the “ACCEPT port RTCA” command must be issued. The remote GPSCard identifies the RTCAB log by the message block identifier contained in the message, and will interpret only the RTCA data portion of the log. NOTE: The CDSA/B logs may be used to monitor the COM port activity and differential data decode success. Initialization - Rover Station It is necessary to initialize the rover receiver to accept observation data from the reference station. If the receiver is not correctly initialized, it will proceed to compute solutions in single point positioning mode. Before initializing, ensure that the data link with the reference station has been properly set up. As well, ensure that the COM port which is to receive the differential data is set up to match the bit rate and protocol settings of the reference station broadcast data. Establishing differential mode of operation at the rover receiver is primarily a one-step process whereby the accept command is used to enable reception of observation data from the reference station. ACCEPT COMMAND The accept command is primarily used to set the GPSCard’s COM port command interpreter for acceptance of various data formats. (see the ACCEPT command in Chapter 2 and Appendix C) Syntax ACCEPT port mode Example: accept com2 rtcm Once intitialized, the rover GPSCard receiver will operate in single point mode until the differential messages are received. If the data messages are lost, the GPSCard will revert to single point positioning until the pseudorange correction messages are restored. NOTES: Ensure that the GPSCard RTCMRULE settings agree with the bit rule being transmitted by the RTCM reference station. Unless otherwise set, all GPSCards default to 6CR. LOG POSITION DATA AND OTHER USEFUL DATA The GPSCard remote receiver has many options for information data logging. To monitor position status, the user may find the PRTKA/B logs to be the most informative. Other options exist, such as POSA/B and GPGGA. As well, velocity data can be found in the VLHA/B, SPHA/B and GPVTG logs. It is really up to the user’s specific applications as to the full range of logs required by the user. MiLLennium Command Descriptions Manual 9 2 Command Descriptions 2 COMMAND DESCRIPTIONS 2 COMMAND DESCRIPTIONS 2.1 GENERAL This section describes all commands accepted by the GPSCard with the exception of the "Special Data Input Commands". They are listed in alphabetical order. For descriptions of output logs using the LOG command, see Chapter 4. The GPSCard is capable of responding to over 50 different input commands. You will find that once you become familiar with these commands, the GPSCard offers a wide range in operational flexibility. All commands are accepted through the COM1 and COM2 serial ports. See Table 2-1 for a complete command listing. NOTE: You will find the HELP command a useful tool for inquiring about the various commands available. The following rules apply when entering commands from a terminal keyboard: • The commands are not case sensitive (COMMAND or command). or help e.g. HELP e.g. FIX POSITION • or fix position All commands and required entries can be separated by a space or a comma (command,variable OR command variable). e.g. datum,tokyo e.g. datum tokyo e.g. fix,position,51.3455323,-117.289534,1002 e.g. fix position 51.3455323 -117.289534 1002 e.g. com1,9600,n,8,1,n,off e.g. com1 9600 n 8 1 n off e.g. log,com1,posa,onchanged e.g. log com1 posa unchanged • At the end of a command or command string, press the key. A carriage return is what the card is looking for and is usually the same as pressing the key. • Most command entries do not provide a response to the entered command. Exceptions to this statement are the VERSION and HELP commands. Otherwise, successful entry of a command is verified by receipt of the COM port prompt (i.e. COM1> or COM2>). The syntax for a command can contain optional parameters (OPT1, OPT2, ...). OPT2 may only be used if it is preceded by OPT1. OPT3 may only be used if it is preceded by OPT2 and so on. Parameters after and including OPT1 will be surrounded by square brackets. An optional parameter such as {hold} surrounded by braces may be used with the log without any preceding optional parameters Example: log com1 posa 60 1 hold log com1 posa hold 10 MiLLennium Command Descriptions Manual 2 Command Descriptions 2.2 COMMAND TABLES Table 2-1 lists the commands by function while Table 2-2 is an alphabetical listing of commands. Please see Appendix C for a more detailed description of individual commands which are listed alphabetically. Table 2-1 Commands By Function Table COMMUNICATIONS, CONTROL AND STATUS Commands Descriptions ANTENNAPOWER COMn Power to the low-noise amplifier of an active antenna COMn port configuration control COMn_DTR COMn_RTS DTR handshaking control RTS handshaking control DIFF_PROTOCOL ➀ Differential Protocol Control FREQUENCY_OUT LOG Variable frequency output (programmable) Logging control MESSAGES RINEX Disable error reporting from command interpreter Configure the user defined fields in the file header RTCMRULE RTCM16T Sets up RTCM bit rule Enters an ASCII message SEND Sends ASCII message to COM port SENDHEX Sends non-printable characters Add an offset to the L1 pseudorange to compensate for signal delays SETL1OFFSET ➀ GENERAL RECEIVER CONTROL AND STATUS Commands Descriptions $ALMA CRESET Download almanac data file Reset receiver to factory default DYNAMICS Set correlator tracking bandwidth HELP RESET On-line command help Performs a hardware reset (OEM only) SAVEALMA SAVECONFIG Saves the latest almanac in NVM Saves current configuration (OEM only) $TM1A Injects receiver time of 1 PPS VERSION Software/hardware information POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL Commands CSMOOTH Descriptions ➀ Sets amount of carrier smoothing DATUM Choose a DATUM name type ECUTOFF Satellite elevation cut-off for solutions FIX HEIGHT Constrains to fixed height (2D mode) FIX POSITION FRESET Constrains to fixed lat, lon, height Clears all data which is stored in NVM $IONA Download ionospheric correction data LOCKOUT $PVAA RTKMODE Deweights a satellite in solutions ➀ Position, velocity and acceleration in ECEF coordinates Setup the RTK mode UNDULATION Ellipsoid-geoid separation USERDATUM User-customized datum ➀ Intended for advanced users of GPS only. MiLLennium Command Descriptions Manual 11 2 Command Descriptions Table 2-1 Commands By Function Table (continued) SATELLITE TRACKING AND CHANNEL CONTROL Commands Descriptions $ALMA Download almanac data file ASSIGN CONFIG Satellite channel assignment Switches the channel configuration of the GPSCard DYNAMICS Sets correlator tracking bandwidth FIX VELOCITY RESETHEALTH Aids high velocity reacquisition Reset PRN health SETHEALTH Overrides broadcast satellite health WAYPOINT NAVIGATION Commands Descriptions MAGVAR Magnetic variation correction SETNAV Waypoint input DIFFERENTIAL REFERENCE STATION Commands Descriptions DGPSTIMEOUT FIX POSITION Sets ephemeris delay Constrain to fixed (reference) LOG Selects required differential-output log POSAVE Implements position averaging for reference station RTCMRULE Selects RTCM bit rule SETDGPSID Set reference station ID DIFFERENTIAL REMOTE STATION Commands Descriptions ACCEPT Accepts RTCM1, RTCA or RTCAB differential inputs $ALMA DGPSTIMEOUT Input almanac data Set maximum age of differential data accepted RESET Performs a hardware reset $RTCA RTCA differential correction input (ASCII) $RTCM RTCM differential correction input (ASCII) RTCMRULE SETDGPSID Selects RTCM bit rule Select differential reference station ID to receive POST PROCESSING DATA Commands Descriptions Depends on operating platform CLOCK INFORMATION, STATUS, AND TIME Commands Descriptions CLOCKADJUST DIFF_PROTOCOL Enable clock modelling & 1PPS adjust ➀ EXTERNALCLOCK EXTERNALCLOCK FREQUENCY SETTIMESYNC $UTCA ➀ 12 ➀ Differential protocol control Sets default parameters of an optional external oscillator Sets clock rate Enable or disable time synchronization Download UTC data Intended for advanced users of GPS only MiLLennium Command Descriptions Manual 2 Command Descriptions Table 2-2 GPSCard Command Summary Command Description $ALMA $IONA $PVAA $REPA $RTCA $RTCM $TM1A $UTCA ACCEPT ANTENNAPOWER ASSIGN UNASSIGN UNASSIGNALL CLOCKADJUST COMn Injects almanac Injects ionospheric refraction corrections Injects latest computed position, velocity and acceleration Injects raw GPS ephemeris data Injects RTCA format DGPS corrections in ASCII (Type 1) Injects RTCM format differential corrections in ASCII (Type 1) Injects receiver time of 1 PPS Injects UTC information Port input control (set command interpreter) Power to the low-noise amplifier of an active antenna Assign a prn to a channel # Un-assign a channel Un-assign all channels Disable clock steering mechanism Initialize Serial Port (1 or 2) COMn_DTR COMn_RTS CONFIG CRESET CSMOOTH DATUM USERDATUM Programmable DTR lead/tail time Programmable RTS lead/tail time Switches the channel configuration of the GPSCard Configuration reset to factory default Sets carrier smoothing Choose a DATUM name type User defined DATUM DGPSTIMEOUT Sets maximum age of differential data to be accepted and ephemeris delay Differential correction message encoding and decoding for implementation in the GPS card firmware DIFF_PROTOCOL DYNAMICS ECUTOFF EXTERNALCLOCK EXTERNALCLOCK FREQUENCY FIX HEIGHT FIX POSITION FIX VELOCITY UNFIX FREQUENCY_OUT FRESET HELP or ? LOCKOUT UNLOCKOUT UNLOCKOUTALL LOG UNLOG UNLOGALL Set receiver dynamics Set elevation cutoff angle Sets default parameters of an optional external oscillator Sets clock rate Sets height for 2D navigation Set antenna coordinates for reference station Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of SVs Remove all receiver FIX constraints Variable frequency output (programmable) Clears all data which is stored in non-volatile memory On-line command help Lock out satellite Restore satellite Restore all satellites Choose data logging type Disable a data log Disable all data logs MiLLennium Command Descriptions Manual Syntax (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) accept port,option antennapower flag assign channel,prn,doppler, search window unassign channel unassignall clockadjust switch comn bps,parity,databits,stopbits, handshake,echo comn_dtr control,active,lead,tail comn_rts control,active,lead,tail config cfgtype creset csmooth value datum option userdatum semi-major,flattening,dx,dy,dz, rx,ry,rz, scale dgpstimeout value value diff_protocol type key or diff_protocol disable or diff_protocol dynamics option [user_dynamics] ecutoff angle externalclock option external frequency clock rate fix height height [auto] fix position lat,lon,height [station id] [health] fix velocity vx,vy,vz unfix frequency_out n,k freset help option or ? option lockout prn unlockout prn unlockoutall log [port],datatype,[trigger],[period],[offset],{hold} unlog [port],data type unlogall [port] 13 2 Command Descriptions Table 2-2 GPSCard Command Summary (continued) MAGVAR MESSAGES POSAVE RESET RINEX RTCM16T Set magnetic variation correction Disable error reporting from command interpreter Implements position averaging for reference station Performs a hardware reset (OEM only) Configure the user defined fields in the file headers EnterValue an ASCII text message to be sent out in the RTCM data Range stream RTCMRULE Set variations of the RTCM bit rule RTKMODE Set up the RTK mode SAVEALMA Save the latest almanac in non-volatile memory SAVECONFIG Save current configuration in non-volatile memory (OEM only) SEND Send an ASCII message to any of the communications ports SENDHEX Sends non-printable characters in hexadecimal pairs SETDGPSID Enter in a reference station ID SETHEALTH Override PRN health RESETHEALTH Reset PRN health RESETHEALTHALL Reset all PRN health SETL1OFFSET Add an offset to the L1 pseudorange to compensate for signal delays SETNAV Set a destination waypoint SETTIMESYNC UNDULATION VERSION 14 Enable or disable time synchronization Choose undulation Current software and hardware information magvar value messages port,option posave maxtime, maxhorstd, maxverstd reset rinex cfgtype rtcm16t ascii message Default rtcmrule rule rrtkmode argument, data range savealma option saveconfig send port ascii-message sendhex port data setdgpsid option sethealth prn,health resethealth prn resethealthall setL1offset distance setnav from lat,from lon,to lat, to lon,track offset, from port,to port settimesync flag undulation separation version MiLLennium Command Descriptions Manual 2 Command Descriptions When the GPSCard is first powered up, or after a FRESET command, all commands will revert to the factory default settings. An example is shown below. The SAVECONFIG command can be used to modify the power-on defaults. Use the RCCA log to reference station command and log settings. Note: All previously stored configurations that were saved to non-volatile memory are erased (including Saved Config, Saved Almanac, and Channel Config). Example: $RCCA,COM1,9600,N,8,1,N,OFF,ON*2B $RCCA,COM1_DTR,HIGH*70 $RCCA,COM1_RTS,HIGH*67 $RCCA,ACCEPT,COMl,COMMANDS*5F $RCCA,COM2,9600,N,8,1,W,OFF,ON*28 $RCCA,COM2_DTR,HIGH*73 $RCCA,COM2_RTS,HIGH*64 $RCCA,ACCEPT,COM2,COMMANDS*58 $RCCA,UNDULATION,TABLE*56 $RCCA,DATUM,WGS84*15 $RCCA,USERDATUM,6378137.000,298.257223563,0.000,0.000,0.000,0.000,0.000,0.000,0.000*6A $RCCA,SETNAV,DISABLE*51 $RCCA,MAGVAR,0.000*33 $RCCA,DYNAMICS,HIGH,AIR*6D $RCCA,UNASSIGNALL*64 $RCCA,UNLOCKOUTALL*20 $RCCA,RESETHEALTHALL*37 $RCCA,UNFIX*73 $RCCA,ANTENNAPOWER ON*1E $RCCA,SETDGPSID,ALL*10 $RCCA,RTCMRULE,6CR*32 $RCCA,RTCM16T*48 $RCCA,CSMOOTH,20.00*7E $RCCA,ECUTOFF,0.00*45 $RCCA,FREQUENCY_OUT,DISlBLE*l2 $RCCA,EXIERRALCLOCK,DISABLE*12 $RCCA,CLOCKADJUST,ENABLE*47 $RCCA,SETTIMESYNC,DISABLE*17 $RCCA,SETL10FFSET, 0. 000000*3F $RCCA,MESSAGES,ALL,ON*67 $RCCA,DGPSTIlMEOUT,60.00,120.00*51 $RCCA,SAVEALMA,ONNEW*4E $RCCA,POSAVE,DISABLE*59 $RCCA,CONFIG,STANDARD*02 $RCCA,DIFF_PROTOCOL,DISABLED*47 MiLLennium Command Descriptions Manual 15 2 Command Descriptions All Commands: Optional calculation of the checksum When an input command is followed by an optional checksum, the checksum will be verified before the command is executed. The checksum is the result of the logical exclusive-OR operation on all the bits in the message. So, the checksum of a command with parameters will change if the parameters are modified. NOTE: The command must be typed in uppercase for the proper checksum to be calculated. As an example, it may be essential to ensure that a receiver has received and executed the correct command from a host computer. If the checksum were calculated by the sender and attached to the command, the receiver would be able to recognize if errors had been introduced and if so, alert the sender to this with an “Invalid Command CRC” message. Example: FIX HEIGHT 4.567[CR][LF] FIX HEIGHT 4.567*66[CR][LF] Both are acceptable, but only the second one would trigger the verification function. All Commands: Response to an invalid command input In an effort to be more descriptive, an invalid command entry now elicits “Invalid Command Name” rather than “Invalid Command Option”. 16 MiLLennium Command Descriptions Manual 3 Special Data Input Commands 3 2SPECIAL DATA INPUT COMMANDS 3 SPECIAL DATA INPUT COMMANDS These entries are data messages that are generated by one GPSCard and sent to another. For example, consider a special configuration in which a GPSCard #1 is able to send these data messages to a GPSCard #2 via a serial port. For GPSCard #1, this is no different than sending these data messages to a file or a screen. Each of these data messages has a special header which is interpreted by GPSCard #2 to mean that the data in that message is to be used as an update of its own GPS parameters such as time, position, velocity, acceleration or knowledge of satellite ephemeris. In this general category also belong the RTCM data messages ($RTCM1A, $RTCM3A, $RTCM9A, $RTCM16A and $RTCM59A). These are describe in further detail in Chapter 6, Message Formats. The injection of special command data can take place via COM1 or COM2. Remember, the source of these special data commands are valid NovAtel ASCII data logs. The special data commands fall into two categories: Almanac Data and Differential Corrections. 3.1 ALMANAC DATA The GPSCard’s standard features include almanac data collection. Following a cold-start boot-up or system reset, the GPSCard will begin a sky search. Once a valid satellite is acquired, the GPSCard will begin almanac downloading and decoding. This process will take at least 12.5 minutes following the cold-start (assuming there are no problems with satellite visibility or the antenna system). It is noted that Ionospheric Correction Data and UTC data are also collected at the same time as almanac data and will also be available following the 12.5 minutes collection period mentioned above. 12 channel OEM cards with the SAVECONFIG option will automatically save almanacs in their non-volatile memory. They will also automatically load the last saved almanac following a cold start or a reset. The card will save an almanac and ionospheric and UTC data received from a satellite if there is no current data in non-volatile memory (NVM), or if the GPS week number of the received data is newer than the week number of the data in NVM. The save will not occur until between 12.5 and 25 minutes have elapsed since the last reset. To check if almanac data is saved in the NVM of the OEM card, check the "almanac data saved" bit in the receiver status word. See the description of the RCSA/B logs, Appendix D for details. The GPSCard is capable of logging almanac data utilizing the NovAtel-format ASCII log command option ALMA. Once logged, the data records will precede the header with the $ character (e.g., $ALMA). There are no specific NovAtel log option commands to independently specify output of ionospheric or UTC parameters. These parameters will always output following the $ALMA log (identifiable by the headers $IONA and $UTCA respectively). See Chapter 4 and Appendix D for more information on the ALMA output log command option. The GPSCard has the capability to accept injection of previously logged NovAtel-format ASCII almanac data ($ALMA, $IONA, and $UTCA). The GPSCard will interpret this log data as special data input commands. This provides the user with the advantage of being able to inject recent almanac data following a cold-start or RESET without having to wait the 12.5 minutes described in above paragraphs. As well, this provides you with faster and more accurate first-fix data because of the advantage of a full almanac being resident immediately following the injection of the special data input commands described above. This is especially beneficial when the receiver is cold-starting in an environment with poor reception and frequent satellite visibility obstruction. There are various ways by which this can be accomplished. • By connecting the COM1 or COM2 port from one GPSCard (reference) directly to the COM1 or port of another GPSCard (remote). The reference card is assumed to be tracking satellites for some time and can be commanded by the ALMA log command option to output almanac records to the remote card. The remote card can be assumed to be just powered-up or RESET and will recognize the $ALMA, $IONA, and $UTCA data as special input commands and update its almanac tables with this new data. COM2 MiLLennium Command Descriptions Manual 17 3 Special Data Input Commands REMEMBER: When connecting two GPSCard COM ports together, the MESSAGES command option should be set to "OFF" to prevent inter-card "chatter". The MiLLennium GPSCard can log current almanac data to a PC connected to its COM1 or COM2 port. Assuming the PC is correctly configured using terminal emulator communications software, then the PC can redirect the GPSCard almanac log to its disk storage device. At a later time following a system restart, the GPSCard can have this almanac.dat file (containing $ALMA, $IONA, and $UTCA records) immediately downloaded as a special input command for immediate use. Refer to the MiLLEnnium GPSCard Guide to Installation and Operating manual for more information about interfacing with the OEM card with a PC. [Note: this procedure will generally not be required with OEM cards as all 12 channel cards now have an almanac save feature built in using non-volatile memory.] $ALMA... Use this special data input command to quickly update the GPSCard almanac tables following a system restart. It is generated from a GPSCard ALMA log and is accepted as the following format: $ALMA,1,3.55148E-003,552960,744,-7.8174E-009,6.10457691E-002,-1.1820041E+000, 1.90436112E+000,-1.8119E-005,-3.6379E-012,1.45854758E-004,2.65602532E+007, 9.55600E-001,1,0,0*0C ... (one record for each valid satellite) ... $ALMA,31,4.90379E-003,552960,744,-7.9660E-009,-3.1044479E+000,6.13853346E-001, 1.92552900E+000,6.67572E-006,3.63797E-012,1.45861764E-004,2.65594027E+007, 9.61670E-001,1,0,0*3F $IONA... Use this special data input command to quickly update the GPSCard ionospheric corrections tables following a system restart (always appended to $ALMA records unless intentionally stripped). This data will ensure that the initial position solutions computed by the GPSCard are as accurate as possible. It is generated from a GPSCard ALMA log and is accepted by any GPSCard as the following format: $IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008, -1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004, 1.966080000000001E+005,-1.966080000000001E+005*02 18 MiLLennium Command Descriptions Manual 3 Special Data Input Commands $UTCA... Use this special data input command to quickly update the GPSCard Universal Time Coordinated (UTC) parameters following a system restart (always appended to $ALMA records unless intentionally stripped). The UTC data is required before the GPSCard can accurately compute UTC time. If not input with $UTCA, it may take up to 12.5 minutes after a reset for the GPSCard to receive current UTCA data. In order to comply with NMEA standards, the GPSCard will null NMEA log data fields until valid UTC parameters are collected or injected by the $UTCA input command. This command is generated from a GPSCard ALMA log and is accepted as the following format: $UTCA,-1.769512891769409E-008,-1.776356839400250E-015,552960,744,755,9,10,5*03 3.2 DIFFERENTIAL CORRECTIONS DATA NovAtel MiLLennium cards can utilize the special data input commands $RTCA and $RTCM. These special data input commands are utilized by a GPSCard operating as a remote station to accept NovAtel ASCII format differential corrections. The data is generated by a GPSCard operating as a reference station with intent to be received by remote stations. To correctly interpret these commands, the remote GPSCard must have its ACCEPT command option set to "COMMANDS" (default). See Appendix A for further information on differential positioning. $PVAA/B XYZ Position, Velocity and Acceleration The $PVAA and PVAB data messages contain the receiver’s latest computed position, velocity and acceleration. These quantities are in rectangular ECEF coordinates based on the centre of the WGS 84 ellipsoid. When a GPSCard receives this data message, it uses the information to update its own position, velocity and acceleration parameters. This would only be needed if the GPSCard could not compute its own position, velocity and acceleration due to signal blockage. This data message helps the receiver reacquire satellites after loss of lock. The data would "steer" the receiver channels to be in the correct state to receive satellites again; thus, the receiver could “follow” the blocked satellites and re-acquire them much more quickly when they become visible again. The position, velocity and acceleration status fields indicate whether or not the corresponding data are valid. Only those messages containing valid data are used by the GPSCard. NOTE 1: NOTE 2: This command is intended for applications involving very high dynamics - where significant position, velocity and acceleration changes can occur during a signal blockage. This data message helps the receiver reacquire satellites after loss of lock. This is a highly complex function, to be used only by advanced users. The ASCII $PVAA data message is generated from a PVAA log, and the binary PVAB data message is generated from a PVAB log. For descriptions of these data messages, please see the description of the PVAA/B logs in Chapter 4 and Appendix D. An example of a $PVAA data message is as follows: $PVAA,845,344559.00,-1634953.141,-3664681.855,4942249.361,-0.025,0.140, 0.078,0.000,-0.000,0.000,1,1,1*02 $REPA/B Raw GPS Ephemeris Data In cases where the receiver does not have an ephemeris for a newly-viewed satellite, these data messages can be used to reduce the time required to incorporate this satellite into the position solution The $REPA and REPB data messages contain the raw binary information for subframes one, two and three from the satellite with the parity information removed. Each subframe is 240 bits long (10 words - 25 bits each) and the log contains a total 720 bits (90 bytes) of information (240 bits x 3 subframes). This information is preceded by the PRN number of the satellite from which it originated. This message will not be generated unless all 10 words from all 3 frames have passed parity. The ASCII $REPA data message is generated from a REPA log, and the binary REPB data message is generated from a REPB log. For descriptions of these data messages, please see the description of the REPA/B logs in Chapter 4 and MiLLennium Command Descriptions Manual 19 3 Special Data Input Commands Appendix D. An example of a $REPA data message is as follows: $REPA,14,8B09DC17B9079DD7007D5DE404A9B2D04CF671C6036612560000021804FD, 8B09DC17B98A66FF713092F12B359DFF7A0254088E1656A10BE2FF125655, 8B09DC17B78F0027192056EAFFDF2724C9FE159675A8B468FFA8D066F743*57[CR][LF] $RTCA... (RTCAA) Use this special data input command to directly input NovAtel RTCAA differential corrections data, ASCII format. The data can be accepted using COM1 or COM2. The differential corrections will be accepted and applied upon receipt of this special data input command. The data is generated from a GPSCard RTCAA log and is accepted by a GPSCard remote station as in the following format: $RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0D207D090808C0E 045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB*20 $RTCM... (RTCMA, $RTCM1A, $RTCM3A, $RTCM9A, $RTCM16A, RTCM59A) Use this special data input command to directly input RTCMA differential correction data, ASCII format (RTCM data converted to ASCII hexadecimal, with NovAtel header added). The data can be accepted using COM1 or COM2. The differential corrections will be accepted and applied upon receipt of this special data input command. See Chapter 6, Message Formats, RTCM Commands and Logs, for further information on RTCM related topics. The data is generated from a GPSCard RTCMA log and is accepted by a GPSCard remote station as in the following format $RTCM,664142404E7257585C6E7F424E757D7A467C47414F6378635552427F73577261624278777F 5B5A525C7354527C4060777B4843637C7F555F6A784155597D7F6763507B77496E7F7A6A426F555C 4C604F4E7F467F5A787F6B5F69506C6D6A4C*2B NOTE : The $RTCA and $RTCM commands allow the user to intermix differential corrections along with other ASCII commands or logs over a single port. (You must, however, ensure that the ACCEPT command option is set to “COMMANDS”.) TIP : The decoding success and status of $RTCA and $RTCM records can be monitored using the CDSA/B data log. These commands will not generate any reply response from the command interpreter. They will simply be processed for valid format and checksum and used internally. If there is any problem with the data, characters missing or checksum fail, the data will be discarded with no warning message. 20 MiLLennium Command Descriptions Manual 3 Special Data Input Commands $TM1A/B Receiver Time of 1PPS The $TM1A and TM1B data messages can be used to time-synchronize multiple receivers which are all referencing the same external oscillator. First, ensure that SETTIMESYNC is enabled. Next, the primary unit must be sending its 1PPS signal to the MARKIN input of the secondary unit. Third, the two units must be communicating via a COM port. In this configuration, the user can send the $TM1A log from a primary to a secondary unit, in a manner similar to that for $ALMA or $UTCA. The secondary unit is then able to compare the time information contained in the log with that of the 1PPS signal, and set its clock even though it may not be tracking any satellites. The ASCII $TM1A data message is generated from a TM1A log, and the binary TM1B data message is generated from a TM1B log. For descriptions of these data messages, please see the description of the TM1A/B logs in Chapter 4 and Appendix D. An example of a $TM1A data message is as follows: $TM1A,794,414634.999999966,-0.000000078,0.000000021,-.999999998,0*57[CR][LF] The $TM1A/B message refers to the 1PPS pulse which has just occurred. In other words TM1A comes after a 1PPS pulse. The length of the pulse for the 24 channel L1/L2 MiLLennium GPSCard is a normally high, active low pulse (1 millisecond), where falling edge is reference. MiLLennium Command Descriptions Manual 21 4 Data Logs 4 4 DATA LOGS DATA LOGS 4.1 OUTPUT LOGGING The GPSCard provides versatility in your logging requirements. You can direct your logs to either COM1 or COM2, or both ports, as well as combine data types. The GPSCard has four major logging formats: • NovAtel Format Data Logs (ASCII/Binary) • NMEA Standard Format Data Logs (ASCII) • RTCM Standard Format Data Logs (Binary) • RTCA Standard Format Data Logs (Binary) All data types can be logged using several methods of triggering each log event. Each log is initiated using the LOG command. The LOG command and syntax are listed below. Syntax: log [port],datatype,[trigger],[period],[offset],{hold} Syntax LOG port datatype trigger period offset hold Description COM1 or COM2 Enter one of the valid ASCII or Binary Data Logs (see later in this chapter and Appendix D) Enter one of the following triggers. ONCE Immediately logs the selected data to the selected port once. Default if trigger field is left blank. ONMARK Logs the selected data when a MARKIN electrical event is detected. Outputs internal buffers at time of mark - does not extrapolate to mark time. Use MKBA/B for extrapolated position at time of mark. ONNEW Logs the selected data each time the data is new even if the data is unchanged. ONCHANGED Logs the selected data only when the data has changed. ONTIME Immediately logs the selected data and then periodically logs the selected data at a frequency [period], [offset] determined by the period and offset parameters. The logging will continue until an UNLOG command pertaining to the selected data item is received (see UNLOG Command). CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer associated with the chosen port becomes empty. The continuously option was designed for use with differential corrections over low bit rate data links. This will provide optimal record generation rates. The next record will not be generated until the last byte of the previous record is loaded into the output buffer of the UART. Use only with theONTIME trigger. Units for this parameter are seconds. The selected period may be any value from 0.05 second to 3600 seconds. Selected data is logged immediately and then periodic logging of the data will start at the next even multiple of the period. If a period of 0.20 sec is chosen, then data will be logged when the receiver time is at the 0.20, 0.40, 0.60 and the next (0.80) second marks. If the period is 15 seconds, then the logger will log the data when the receiver time is at even 1/4 minute marks. The same rule applies even if the chosen period is not divisible into its next second or minute marks. If a period of 7 seconds is chosen, then the logger will log at the multiples of 7 seconds less than 60, that is, 7, 14, 21, 28, 35, 42, 49, 56 and every 7 seconds thereafter. Use only with the ONTIME trigger. Units for this parameter are seconds. It provides the ability to offset the logging events from the above startup rule. If you wished to log data at 1 second after every minute you would set the period to 60 seconds and the offset to 1 second (Default is 0). Will prevent a log from being removed when the UNLOGALL command is issued Example LOG COM1 POSA ONTIME 60 1 HOLD Example: log com1,posa,ontime,60,1 If the LOG syntax does not include a trigger type, it will be output only once following execution of the LOG command. If trigger type is specified in the LOG syntax, the log will continue to be output based on the trigger specification. Specific logs can be disabled using the UNLOG command, whereas all enabled logs will be disabled 22 MiLLennium Command Descriptions Manual 4 Data Logs by using the UNLOGALL command (see Chapter 2 and Appendix C). All activated logs will be listed in the receiver configuration status log (RCCA). 4.2 NovAtel FORMAT DATA LOGS General The GPSCard is capable of executing more than 40 NovAtel format log commands. Each log is selectable in ASCII and Binary formats. The one exception to this rule is the RGE log, which can be logged as RGED. The “D” indicates a compressed binary format to allow higher speed logging. Any format can be selected individually or simultaneously over the same COMn ports. All of the log descriptions are listed in alphabetical order in Appendix D. Each log first lists the ASCII format, followed by the Binary format description. ASCII Log Structure Log types ending with the letter A (or a) will be output in ASCII format (e.g., POSA). The structures of all ASCII logs follow the general conventions as noted here: 1. 2. 3. The lead code identifier for each record is '$'. Each log is of variable length depending on amount of data and formats. All data fields are delimited by a comma ',' with the exception of the last data field, which is followed by a * to indicate end of message data. Each log ends with a hexadecimal number preceded by an asterisk and followed by a line termination using the carriage return and line feed characters, e.g., *xx[CR][LF]. This 8-bit value is an exclusive OR (XOR) of all bytes in the log, excluding the '$' identifier and the asterisk preceding the two checksum digits. 4. Structure:: $xxxx, data field..., data field..., data field... *xx [CR][LF] Binary Log Structure Log types ending with the letter B (or b) will be output in Binary format (e.g., POSB). The structures of all Binary logs follow the general conventions as noted here: 1. Basic format of: 2. The Sync bytes will always be: Byte First Second Third 3. 4. 5. Hex AA 44 11 Sync Checksum Message ID Message byte count Data 3 bytes 1 byte 4 bytes unsigned integer 4 bytes unsigned integer x Decimal 170 68 17 The Checksum is an XOR of all the bytes (including the 12 header bytes) with result = 00. The Message ID identifies the type of log to follow. The Message byte count equals the total length of the data block including the header. NOTE: Maximum flexibility for logging data is provided to the user by these logs. The user is cautioned, however, to recognize that each log requested requires additional CPU time and memory buffer space. Too many logs may result in lost data and degraded CPU performance. CPU overload can be monitored using the idle-time and buffer overload bits from the RCSA/B log. See Table D-5 (GPSCard Receiver Self-test Status Codes). MiLLennium Command Descriptions Manual 23 4 Data Logs The following table describes the format types used in the description of binary logs. Type Size (bytes) Size (bits) char 1 8 int 4 32 double 8 64 float 4 32 Description The char type is used to store the integer value of a member of the representable character set. That integer value is the ASCII code corresponding to the specified character. The size of a signed or unsigned int item is the standard size of an integer on a particular machine. On a 32-bit processor (such as the NovAtel GPSCard), the int type is 32 bits, or 4 bytes. The int types all represent signed values unless specified otherwise. Signed integers are represented in two's-complement form. The most-significant bit holds the sign: 1 for negative, 0 for positive and zero. The double type contains 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa. Its range is ±1.7E308 witrh at least 15 digits of precision. The float type contains 32 bits: 1 for the sign, 8 for the exponent, and 23 for the mantissa. Its range is ±3.4E38 with at least 7 digits of precision. Each byte within an int has its own address, and the smallest of the addresses is the address of the int. The byte at this lowest address contains the eight least significant bits of the doubleword, while the byte at the highest address contains the eight most significant bits. The following illustration shows the arrangement of bytes within words and doublewords. Similarly the bits of a "double" type are stored least significant byte first. This is the same data format used by IBM PC computers. 7 0 char address n 31 23 15 7 0 int n+3 62 double S Biased Exponent 63 n+7 n+2 55 51 22 S Biased Exponent 31 n+3 47 52 n+6 30 float n+1 address n 39 n+5 15 two’s complement 31 23 15 52-bits mantissa n+4 7 n+3 n+2 7 n+1 address n 0 0 0 23-bits mantissa 23 n+2 n+1 address n 4.3 RTK After setting up your system and initializing the positioning algorithms, as described in the RTK section of Chapter 1. You can use the logs listed in this section to record the data collected. The low-latency-solution logs (e.g. PRTKA/B) are recommended for kinematic users, while the matched-solution logs (e.g. RTKA/B) are recommended for stationary users. For a discussion on low-latency and matched solutions, see the Differential Positioning section in Appendix A. A matched solution is always a carrier-phase differential solution, and consequently offers the greatest possible accuracy. A low-latency solution, on the other hand, is the best one that is currently available; the possibilities are categorized as follows, starting with the one offering the greatest accuracy and precision: 1. Carrier-phase differential solution 2. Pseudorange differential solution 3. Single-point solution Therefore, if an RTK solution is not available, then a low-latency-solution log will contain a pseudorange differential solution if it exists. If neither an RTK nor a pseudorange differential solution is available, then a lowlatency-solution log will contain a single-point solution. 24 MiLLennium Command Descriptions Manual 4 Data Logs 4.4 NMEA FORMAT DATA LOGS General The NMEA log structures follow format standards as adopted by the National Marine Electronics Association. The reference document used is "Standard For Interfacing Marine Electronic Devices NMEA 0183 Version 2.00". For further information, see Appendix F, Standards and References. The following table contains excerpts from Table 6 of the NMEA Standard which defines the variables for the NMEA logs. The actual format for each parameter is indicated after its description. Field Type Symbol Definition Special Format Fields Status A Latitude llll.ll Longitude yyyyy.yy Time hhmmss.ss Defined field Single character field: A = Yes, Data Valid, Warning Flag Clear V = No, Data Invalid, Warning Flag Set Fixed/Variable length field: degrees|minutes.decimal - 2 fixed digits of degrees, 2 fixed digits of minutes and a variable number of digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to maintain fixed length. The decimal point and associated decimal-fraction are optional if full resolution is not required. Fixed/Variable length field: degrees|minutes.decimal - 3 fixed digits of degrees, 2 fixed digits of minutes and a variable number of digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to maintain fixed length. The decimal point and associated decimal-fraction are optional if full resolution is not required Fixed/Variable length field: hours|minutes|seconds.decimal - 2 fixed digits of hours, 2 fixed digits of minutes, 2 fixed digits of seconds and variable number of digits for decimal-fraction of seconds. Leading zeros always included for hours, minutes and seconds to maintain fixed length. The decimal point and associated decimalfraction are optional if full resolution is not required. Some fields are specified to contain pre-defined constants, most often alpha characters. Such a field is indicated in this standard by the presence of one or more valid characters. Excluded from the list of allowable characters are the following which are used to indicate field types within this standard: "A", "a", "c", "hh", "hhmmss.ss", "llll.ll", "x", "yyyyy.yy" Numeric Value Fields Variable numbers x.x Fixed HEX field hh___ Variable length integer or floating numeric field. Optional leading and trailing zeros. The decimal point and associated decimal-fraction are optional if full resolution is not required (example: 73.10 = 73.1 = 073.1 = 73) Fixed length HEX numbers only, MSB on the left Information Fields Variable text c--c Variable length valid character field. Fixed alpha field aa___ Fixed length field of uppercase or lowercase alpha characters Fixed number xx___ Fixed length field of numeric characters Fixed text field cc___ Fixed length field of valid characters NOTES: 1. 2. 3. 4. 5. Spaces may only be used in variable text fields. A negative sign "-" (HEX 2D) is the first character in a Field if the value is negative. The sign is omitted if value is positive. All data fields are delimited by a comma (,). Null fields are indicated by no data between two commas (,,). Null fields indicate invalid or no data available. The NMEA Standard requires that message lengths be limited to 82 characters. MiLLennium Command Descriptions Manual 25 4 Data Logs 4.5 GPS TIME VS LOCAL RECEIVER TIME All logs report GPS time expressed in GPS weeks and seconds into the week. The time reported is not corrected for local receiver clock error. To derive the closest GPS time, one must subtract the clock offset shown in the CLKA log (field 4) from GPS time reported. GPS time is based on an atomic time scale. Universal Time Coordinated (UTC) time (reported in NMEA logs) is also based on an atomic time scale, with an offset of seconds applied to coordinate Universal Time to GPS time. GPS time is designated as being coincident with UTC at the start date of January 6, 1980 (00 hours). GPS time does not count leap seconds, and therefore an offset exists between UTC and GPS time (at this date: 10 seconds). The GPS week consists of 604800 seconds, where 000000 seconds is at Saturday midnight. Each week at this time, the week number increments by one, and the seconds into the week resets to 0. (See Appendix H, Some Common Unit Conversions, for an example) 4.6 LOG TABLES Table 4-1 lists the logs by function while Table 4-2 is an alphabetical listing of logs. Please see Appendix D for a more detailed description of individual NovAtel and NMEA format logs which are listed alphabetically. RTCM and RTCA format data logs can be found in Chapter 6, Message Formats while receiver-independant RINEX logs will be found in Chapter 7. Special Pass-Through logs are found in the next chapter, Chapter 5. Table 4-1 Logs By Function Table COMMUNICATIONS, CONTROL AND STATUS Logs Descriptions CDSA/B COM port communications status COM1A/B COM2A/B Log data from COM1 Log data from COM2 COMnA/B RCSA/B Pass-through data logs Receiver self-test status RTCM16T NovAtel ASCII format special message RTCM16 RTCM format special message GENERAL RECEIVER CONTROL AND STATUS Logs Descriptions PVAA/B Receiver’s latest computed position, velocity and acceleration in ECEF coordinates RCCA Receiver configuration status RCSA/B Version and self-test status RVSA/B VERA/B Receiver status Receiver hardware and software version numbers POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL Logs Descriptions DOPA/B GGAB DOP of SVs currently tracking GPS fix data GPGGA NMEA, position data GPGLL GPGRS NMEA, position data NMEA, range residuals GPGSA GPGST NMEA, DOP information NMEA, measurement noise statistics MKPA/B POSA/B Position at time of mark Position data PRTKA/B Computed position PXYA/B RTKA/B Position (Cartesian x,y,z coordinates) Computed position SPHA/B Speed and direction over ground 26 MiLLennium Command Descriptions Manual 4 Data Logs Table 4-1 Logs By Function Table (continued) SATELLITE TRACKING AND CHANNEL CONTROL Logs Descriptions ALMA/B Current decoded almanac data DOPA/B ETSA/B DOP of SVs currently tracking Provides channel tracking status information for each of the GPSCard parallel channels GPALM NMEA, almanac data GPGSA GPGSV NMEA, SV DOP information NMEA, satellite-in-view information RALA/B RASA/B Raw almanac Raw GPS almanac set RGEA/B/D Satellite range measurements SATA/B Satellite specific information SVDA/B SV position (ECEF xyz) WAYPOINT NAVIGATION Logs Descriptions GPRMB NMEA, waypoint status GPRMC NMEA, navigation information GPVTG NMEA, track made good and speed GPZTG MKPA/B NMEA, time to destination Position at time of mark input NAVA/B POSA/B Navigation waypoint status Position data SPHA/B Speed and course over ground VLHA/B Velocity, latency & direction over ground DIFFERENTIAL REFERENCE STATION Logs Descriptions ALMA/B Current almanac information CDSA/B PAVA/B COM port data transmission status Parameters being used in the position averaging process RGEA/B/D RPSA/B Channel range measurements Reference station position and health RTCAA/B Transmits RTCA differential corrections in NovAtel ASCII or Binary RTCM1 RTCM3 Transmits RTCM SC104 standard corrections Reference position RTCM59 RTCMA/B NovAtel format RT-20 observation data Transmits RTCM information in NovAtel ASCII/binary SATA/B Satellite specific information DIFFERENTIAL REMOTE STATION Logs Descriptions CDSA/B GPGGA Communication and differential decode status NMEA, position fix data GGAB POSA/B NovAtel binary version of GPGGA Position information PRTKA/B RTKA/B Computed Position – best available Computed Position – Time Matched RTKOA/B RTK Output SATA/B SVDA/B Satellite specific information SV position in ECEF XYZ with corrections VLHA/B Velocity, latency & direction over ground MiLLennium Command Descriptions Manual 27 4 Data Logs Table 4-1 Logs By Function Table (continued) POST PROCESSING DATA Logs Descriptions BSLA/B Most recent matched baseline expressed in ECEF coords. CLKA/B Receiver clock offset information REPA/B Raw ephemeris information RGEA/B/D SATA/B Satellite and ranging information Satellite specific information SVDA/B SV position in ECEF XYZ with corrections CLOCK INFORMATION, STATUS, AND TIME Logs Descriptions CLKA/B CLMA/B Receiver clock offset information ➀ Current clock-model matrices of the GPSCard GPZDA GPZTG NMEA, UTC time and date NMEA, UTC and time to waypoint MKTA/B TM1A/B Time of mark input Time of 1PPS ➀ Intended for advanced users of GPS only. Table 4-2 GPSCard Log Summary Syntax: log port,datatype,[trigger],[period],[offset],{hold} NovAtel Format Logs Datatype Description Datatype Description ALMA/B Decoded Almanac RALA/B Raw Almanac BSLA/B Baseline Measurement RASA/B Raw GPS Almanac Set CDSA/B Communication and Differential Decode Status RCCA Receiver Configuration CLKA/B Receiver Clock Offset Data REPA/B Raw Ephemeris CLMA/B Receiver Clock Model RGEA/B/D Channel Range Measurements COM1A/B Log data from COM1 RPSA/B Reference Station Position and Health COM2A/B Log data from COM2 RTCAA/B RTCA format Differential Corrections with NovAtel headers DOPA/B Dilution of Precision RTKA/B Computed Position - Time Matched ETSA/B Extended Tracking Status RTKOA/B RTK Solution Parameters GGAB Global Position System Fix Data - Binary Format RTCMA/B RTCM Type 1 Differential Corrections with NovAtel headers MKPA/B Mark Position RTCM16T Special Message MKTA/B Time of Mark Input RVSA/B Receiver Status NAVA/B Navigation Data SATA/B Satellite Specific Data PAVA/B Positioning Averaging Status SPHA/B Speed and Direction Over Ground POSA/B Computed Position SVDA/B SV Position in ECEF XYZ Coordinates with Corrections PRTKA/B Computed Position TM1A/B Time of 1PPS PVAA/B XYZ Position, Velocity and Acceleration VERA/B Receiver Hardware and Software Version Numbers PXYA/B Computed Cartesian Coordinate Position VLHA/B Velocity, Latency, and Direction over Ground 28 MiLLennium Command Descriptions Manual 4 Data Logs Table 4-2 GPSCard Log Summary (continued) NMEA Format Logs GPALM Almanac Data GPGSV GPS Satellites in View GPGGA Global Position System Fix Data GPRMB Generic Navigation Information GPGLL Geographic Position - lat/lon GPRMC GPS Specific Information GPGRS GPS Range Residuals for Each Satellite GPVTG Track Made Good and Ground Speed GPGSA GPS DOP and Active Satellites GPZDA UTC Time and Date GPGST Pseudorange Measurement Noise Statistics GPZTG UTC & Time to Destination Waypoint RTCA Format RTCA RTCA Differential Corrections: Type 1 and Type 7 RTCM Format RTCM1 Type 1 Differential GPS Corrections RTCM3 Type 3 Reference Station Parameters RTCM9 Type 9 Partial Satellite Set Differential Corrections RTCM16 Type 16 Special Message RTCM59 Type 59N-0 NovAtel Proprietary Message: RT20 Differential Observations N.B. A/B/D: A refers to GPSCard output logs in ASCII format. B refers to GPSCard output logs in Binary format. D refers to GPSCard output logs in compressed binary format. MiLLennium Command Descriptions Manual 29 5 Special Pass-Through Logs 5 SPECIAL PASS-THROUGH LOGS 5 SPECIAL PASS-THROUGH LOGS The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a specified port (COM1 or COM2) to any specified GPSCard port (COM1 or COM2). This capability, in conjunction with the SEND command, can allow the GPSCard to perform bi-directional communications with other devices such as a modem, terminal, or another GPSCard. There are two pass-through logs COM1A/B and COM2A/B, available on MiLLennium GPSCards. Pass-through is initiated the same as any other log, i.e., LOG [to-port] [data-type-A/B] [trigger]. However, passthrough can be more clearly specified as: LOG [to-port] [from-port-A/B] [onchanged]. Now, the [from-port-A/B] field designates the port which accepts data (i.e., COM1or COM2) as well as the format in which the data will be logged by the [to-port] — (A for ASCII or B for Binary). When the [from-port-A/B] field is designated with an [A], all data received by that port will be redirected to the [to-port] in ASCII format and will log according to standard NovAtel ASCII format. Therefore, all incoming ASCII data will be redirected and output as ASCII data. However, any binary data received will be converted to a form of ASCII hexadecimal before it is logged. When the [from-port-A/B] field is designated with a [B], all data received by that port will be redirected to the [toport] exactly as it is received. The log header and time-tag adhere to standard NovAtel Binary Format followed by the pass-through data as it was received (ASCII or binary). Pass-through logs are best utilized by setting the [trigger] field as onchanged or onnew. Either of these two triggers will cause the incoming data to log when any one of the following conditions is met: • Upon receipt of a character • Upon receipt of a character • Upon receipt of 80 characters • 1/2 second timeout following receipt of last character Each pass-through record transmitted by the GPSCard is time tagged by the GPSCard clock in seconds. GPS weeks and For illustration purposes, you could connect two GPSCards together via their COM1 ports such as in a reference station, labelled as reference station in Figure 5-1, to remote station scenario. If the reference station were logging PVAA data to the remote station, it would be possible to use the pass-through logs to pass through the received PVAA differential correction data to a disk file (let's call it DISKFILE.log) at the remote station host PC hard disk. 30 MiLLennium Command Descriptions Manual 5 Special Pass-Through Logs Figure 5-1 Pass-Through Log Data $PVAA data log Data Link To COM1 To COM1 To COM2 To COM2 fix position (lat,lon,ht,id) accept com1 none log com1 pvaa ontime 5 messages com1 off log console com1a onchanged Serial Cable Serial Cable Host PC (Rover Station) Host PC (Reference Station) When pass-through logs are being used, the GPSCard's command interpreter continues to monitor the port for valid input commands and replies with error messages when the data is not recognized as such. If you do not want the pass-through input port to respond with error messages during unrecognized data input, see the MESSAGES command, Appendix C for details on how to inhibit the port's error message responses. As well, if you do not want the reference station to accept any input from the remote device, use the ACCEPT NONE command to disable the port's command interpreter. 5.1 COMMAND SYNTAX Syntax: log to-port from-port-A/B trigger Syntax Range Value Description log to-port from-port-[A/B] — COM1, COM2 COM1A/B, COM2A/B trigger onchanged or onnew Log command Port that will output the pass-through log data Port that will accept input data; [A] option logs data as ASCII, [B] option logs data with binary header log will output upon receipt of : , , 80 characters, or 1/2 sec. timeout Default unlogall — — — Example 1: log com2 com1a onchanged MiLLennium Command Descriptions Manual 31 5 Special Pass-Through Logs 5.2 ASCII LOG STRUCTURE $port ID week Field # Field type 1 $port ID 2 3 4 week seconds pass-through data 5 6 *xx [CR][LF] seconds pass-through data Data Description *xx [CR][LF] Example Log header: Identifies port accepting input data GPS week number GPS seconds into the week at time of log Data accepted into COM1 (up to 80 characters) Checksum Sentence terminator $COM1 747 347131.23 $TM1A,747,347131.000000000, 0.000000058,0.000000024, -9.000000009,0*78 *2E [CR][LF] Example 1: $COM1,747,347131.23,$TM1A,747,347131.000000000,0.000000058,0.00000 0024, -9.000000009,0*78 *2E[CR][LF] $COM1,747,347131.31, *4F[CR][LF] $COM1,747,347131.40,Invalid Command Option *7C[CR][LF] $COM1,747,347131.42,Com1>Invalid Command Option *30[CR][LF] $COM1,747,347131.45,Com1>*0A[CR][LF] Example 1, above, shows what would result if a GPSCard logged TM1A data into the COM1 port of another GPSCard, where the accepting card is redirecting this input data as a pass-through log to its COM2 port (log com2 com1a onchanged). Under default conditions the two cards will "chatter" back and forth with the Invalid Command Option message (due to the command interpreter in each card not recognizing the command prompts of the other card). This chattering will in turn cause the accepting card to transmit new pass-through logs with the response data from the other card. To avoid this chattering problem, use the GPSCard MESSAGES command on the accepting port to disable error reporting from the receiving port command interpreter or if the incoming data is of no use to the GPSCard, then disable the command interpreter with the ACCEPT NONE command. If the accepting port's error reporting is disabled by creating two records as follows: MESSAGES OFF, the $TM1A data record would pass through Example 1a: $COM1,747,347204.80,$TM1A,747,347203.999999957,0.000000015,0.000000024, -9.000000009,0*55 *00[CR][LF] $COM1,747,347204.88, *48[CR][LF] The reason that two records are logged from the accepting card is because the first record was initiated by receipt of the $TM1A log's first terminator . Then the second record followed in response to the $TM1A log's second terminator . Note that the time interval between the first character received ($) and the terminating can be calculated by differencing the two GPS time tags (0.08 seconds). This pass-through feature is useful for time tagging the arrival of external messages. These messages could be any user-related data. If the user is using this feature for tagging external events then it is recommended that the command interpreter be disabled so that the GPSCard does not respond to the messages. See the ACCEPT command in Chapter 2 and Appendix C. Example 1b illustrates what would result if $TM1B binary log data were input to the accepting port (i.e., log com2 com1a onchanged). 32 MiLLennium Command Descriptions Manual 5 Special Pass-Through Logs Example 1b: $COM1,747,349005.18, D k 4 3M A <83> o<82> Z <97>I <91> iV><7F><8F>O " *6A As can be seen, the $TM1B binary data at the accepting port was converted to a variation of ASCII hexadecimal before it was passed through to COM2 port for logging (MESSAGES command set to OFF). 5.3 BINARY LOG STRUCTURE Format: Field # 1 (header) 2 3 4 Message ID = 30 for COM1B 31 for COM2B Message byte count = 24 + (length of pass-through data string received (80 maximum)) Data Sync Checksum Message ID Message byte count Week number Seconds of week Pass-through data as received Bytes 3 1 4 4 4 8 variable MiLLennium Command Descriptions Manual Format char char integer integer integer double char Units weeks seconds Offset 0 3 4 8 12 16 24 + (variable data) 33 6 Message Formats 6 MESSAGE FORMATS 6 MESSAGE FORMATS In a NovAtel RTK positioning system, the observations transmitted by a NovAtel reference station to a NovAtel remote station can be in either a proprietary RTCA Type 7 or a proprietary RTCM Type 59N message format. Table 6-1 illustrates the various combinations of hardware and message formats, together with the positioning mode (RT-20 or RT-2) which will result: Table 6-1 Positioning Modes Reference station: L1 RTCM Type 59N Reference station: L1 RTCA Type 7 Reference station: L1 & L2 RTCM Type 59N Reference station: L1 & L2 RTCA Type 7 Remote station: L1 RT-20 RT-20 RT-20 RT-20 Remote station: L1 & L2 RT-20 RT-20 RT-20 RT-2 The following information can be used to calculate the minimum data throughput required of the communications data link. Keep in mind that manufacturers of communication equipment add extra bits to each message (e.g. for error detection), forming an “overhead” that must be taken into account; also, radio transmitting equipment may have a duty cycle which must also be factored into the calculations. Thus, a “4800 bits per second” radio modem might actually sustain only 2000 bits per second. Consult the documentation supplied by the manufacturer of your communications equipment. 6.1 RTCA-FORMAT MESSAGES NovAtel has defined two proprietary RTCA Standard Type 7 binary-format messages1, RTCAOBS and RTCAREF, for reference station transmissions. These can be used with either single or dual-frequency NovAtel receivers; existing users of RT-20 wishing to switch from RTCM to RTCA message formats will require a software upgrade. The RTCA message format outperforms the RTCM format in the following ways, among others: • a more efficient data structure (lower overhead) • better error detection • allowance for a longer message, if necessary RTCAREF and RTCAOBS, respectively, correspond to the RTCM Type 3 and Type 59 logs used in singlefrequency-only measurements. Both are NovAtel-proprietary RTCA Standard Type 7 messages with an ‘N’ primary sub-label. RTCAOBS TYPE 7 An RTCAOBS (RTCA Reference-Station Satellite Observations) message contains reference station satellite observation information. It is used to provide range observations to the remote receiver, and should be sent every 1 or 2 seconds. This log is made up of variable-length messages up to 255 bytes long. The maximum number of bits in this message is [140 + (92 x N)], where N is the maximum number of satellite record entries transmitted. Using the RTKMODE command, you can define N to be anywhere from 4 to 20; the default value is 12. 1. For further information on RTCA Standard Type 7 messages, you may wish to refer to: Minimum Aviation System Performance Standards - DGNSS Instrument Approach System: Special Category I (SCAT-I), Document No. RTCA/DO-217 (April 19, 1995); Appendix A, page 21 34 MiLLennium Command Descriptions Manual 6 Message Formats RTCAREF TYPE 7 An RTCAREF (RTCA Reference Station Position Information) message contains reference station position information, and should be sent once every 10 seconds. Each message is 24 bytes (192 bits) long. If RTCA-format messaging is being used, the optional station id field that is entered using the FIX POSITION command can be any 4-character string combining numbers and upper-case letters, and enclosed in quotation marks (e.g. “RW34”). Note that the representation of this string in the log message would be a number within the range of 266,305 to 15,179,385 as per RTCA notation. The lower bound of 266,305 represents “AAAA” and the upper bound of 15,179,385 represents “9999”. RTCA STANDARD LOGS The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential Global Navigation Satellite System (DGNSS) Special Category I (SCAT-I) precision instrument approaches. The RTCA Standard is in a preliminary state. Described below is NovAtel’s current support for this Standard. It is based on "Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I (SCAT-I)" dated August 27, 1993 (RTCA/DO-217). RTCA This log enables transmission of RTCA Standard format Type 1 messages from the GPSCard when operating as a reference station. Before this message can be transmitted, the GPSCard FIX POSITION command must be set. The RTCA log will be accepted by a GPSCard operating as a remote station over a COM port after an ACCEPT port RTCA command is issued. The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction (Type 1) messages accepted by the remote station cannot be greater than 22 seconds. See the DGPSTIMEOUT command in Chapter 2 and Appendix C for information regarding DGPS delay settings. The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new ephemeris before transmitting differential corrections. See the DGPSTIMEOUT command for information regarding ephemeris delay settings. The basic SCAT-I Type 1 differential correction message is as follows: Format: Message length = 11 + (6*obs) : (83 bytes maximum) Field Type SCAT-I header Data – – – Message block identifier Reference station ID Message type Bits Bytes 8 24 8 6 8 13 3 2 (this field will always report 00000001) Type 1 header – – – Message length Mofdified z-count Acceleration error bound (In the GPSCard, this field will report 000) Type 1 data CRC – Satellite ID – Pseudorange correction ➀ – Issue of data – Range rate correction ➀ – UDRE Cyclic redundancy check 6 16 8 12 6 6 *obs 3 ➀ The pseudorange correction and range rate correction fields have a range of ±655.34 metres and ±4.049 m/s respectively. Any satellite which exceeds these limits will not be included. RTCAA This log contains the same data available in the RTCA SCAT-I message, but has been modified to allow flexibility in using the RTCA data. The RTCA data has been reformatted to be available in ASCII hexadecimal, utilizing a NovAtel header and terminates with a checksum. MiLLennium Command Descriptions Manual 35 6 Message Formats This message was designed so that RTCA data can be intermixed with other NovAtel ASCII data over a common communications port. The log is not in pure RTCA format. The header ($RTCA) and terminator (*xx) must be stripped off at the receiving end, then the data will need to be converted from hexadecimal to binary before the RTCA information is retrieved. The RTCAA log can be directly decoded by other NovAtel GPSCard receivers operating as remote stations. They will recognize the $RTCA header as a special data input command and the differential corrections data will be directly applied. The GPSCard remote station receiving this log must have the ACCEPT command set to "ACCEPT port COMMANDS". Structure: $RTCA data *xx Field # Field Type 1 2 3 4 [CR][LF] Data Description Example $RTCA data Log header SCAT-I type 1 differential corrections *x x [CR][LF] Checksum $RTCA 990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9 FD071AFC7FA0D207D090808C0E045BACC055E9075271FFB 0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB *20 [CR][LF] Example: $RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0 D207D090808C0E045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074F CF3C940504052DFB*20[CR][LF] RTCAB The RTCAB log contains the SCAT-I differential corrections message with the standard NovAtel binary log preamble (header) added. The RTCAB log will be accepted by the GPSCard over a COM port after an "ACCEPT port RTCA" command is issued. Format: Field # 1 (header) 2 3 4 5 6 Message ID = 38 Data Message byte count = 12 + (11+(6*obs)) : 95 bytes maximum Bytes Format Sync 3 char Checksum 1 char Message ID 4 integer Message byte count 4 integer – Message block idenifier 6 – Reference station ID – Message type – Message length – Modified z-count 2 – Acceleration error bound – Satellite ID – Pseudorange correction 6 – Issue of data – Range rate correction – UDRE Next PRN offset = 26 + (6*obs) where obs varies from 0 to (obs-1) CRC 3 Offset 0 3 4 8 12 18 20 6.2 RTCM-FORMAT MESSAGES RTCM SC-104 Type 3 & 59 messages2 can be used for reference station transmissions in differential systems. However, since these messages do not include information on the L2 component of the GPS signal, they cannot be used with RT-2 positioning. Regardless of whether single or dual-frequency receivers are used, the RT-20 36 MiLLennium Command Descriptions Manual 6 Message Formats positioning algorithm would be used. This is for a system in which both the reference and remote stations utilize NovAtel receivers. Note that the error-detection capability of an RTCM-format message is less than that of an RTCA-format message. The communications equipment that you use may have an error-detection capability of its own to supplement that of the RTCM message, although at a penalty of a higher overhead (see the discussion at the beginning of this chapter). Consult the vendor’s documentation for further information. • RTCM Type 3 Reference Station Position A Type 3 message contains reference station position information. This message must be sent at least once every 30 seconds, although it is recommended that it be sent once every 10 seconds. It uses four RTCM data words following the two-word header, for a total frame length of six 30-bit words (180 bits). • RTCM Type 59 NovAtel Proprietary (RT-20) A Type 59N message contains reference station satellite observation information, and should be sent once every 2 seconds. It is variable in size, and can be up to thirty three 30-bit words (990 bits) long. If RTCM-format messaging is being used, the optional station id field that is entered using the FIX POSITION command can be any number within the range of 0 - 1023 (e.g. 119). The representation in the log message would be identical to what was entered. RTCM STANDARD COMMANDS and LOGS The Global Positioning System is a world-wide positioning service developed by the U.S. Department of Defense (DOD) and is operated and maintained by the U.S. Air Force Space Division. As usage of the GPS Standard Positioning Service (SPS) has gained world wide commercial acceptance, the applications have become wide and varied. Of special importance have been the developments in the use of differential GPS (DGPS). DGPS enables system users to leap from nominal 100 metre system accuracies (single point) to the more desirable one to five metre nominal accuracies possible from utilizing differential corrections between reference and remote stations. As DGPS systems exist all over the world, the need arose to establish a set of operating standards that all DGPS receivers could use for the purpose of transmitting and receiving differential corrections between GPS receivers of various types, regardless of receiver design or manufacturer. The Radio Technical Commission for Maritime Services (RTCM) was established to facilitate the establishment of various radio navigation standards, which includes recommended GPS differential standard formats. The standards recommended by the Radio Technical Commission for Maritime Services Special Committee 104, Differential GPS Service (RTCM SC-104,Washington, D.C.), have been adopted by NovAtel for implementation into the GPSCard. Because the GPSCard is capable of utilizing RTCM formats, it can easily be integrated into positioning systems around the globe. As it is beyond the scope of this manual to provide in-depth descriptions of the RTCM data formats, it is recommended that anyone requiring explicit descriptions of such, should obtain a copy of the published RTCM specifications. See Appendix F for reference information. 2. For further information on RTCM SC-104 messages, you may wish to refer to: RTCM Recommended Standards for Differential Navstar GPS Service, Version 2.1, RTCM Paper 194-93/SC104STD (January 3, 1994) MiLLennium Command Descriptions Manual 37 6 Message Formats RTCM General Message Format All GPSCard RTCM standard format logs adhere to the structure recommended by RTCM SC-104. Thus, all RTCM message are composed of 30 bit words. Each word contains 24 data bits and 6 parity bits. All RTCM messages contain a 2-word header followed by 0 to 31 data words for a maximum of 33 words (990 bits) per message Message Frame Header Data Bits Word 1 – – – – Message frame preamble for synchronization Fram/message type ID reference station ID Parity 8 6 10 6 Word 2 – – – – – Modified z-count (time tag) Sequence number Length of message frame reference station health Parity 13 3 5 3 6 The remainder of this section will provide further information concerning GPSCard commands and logs that utilize the RTCM data formats. RTCM Standard Commands RTCMRULE The RTCM standard states that all equipment shall support the use of the "6 of 8" format (data bits a1 through a6 where bits a1 through a6 are valid data bits and bit a7 is set to mark and bit a8 is set to space). The GPSCard RTCMRULE command allows for flexibility in the use of the bit rule to accommodate compatibility with equipment that does not strictly adhere to the RTCM stated rule. Syntax: RTCMRULE rule Syntax Range Value RTCMRULE rule 6CR 6SP 6 8 Description Command 6CR is for 6 bits of valid data per byte. Each frame is followed by a character. 6SP (6 bit special); the RTCM decoder of the remote receiver will ignore the two MSB of the data and hence all 6 bit data will be accepted. This allows users with non-conforming 6 bit rule data to use the NovAtel receiver to accept their RTCM data. The user will not be allowed to enter extra control data such as CR/LF, as this will be treated as RTCM data and cause the parity to fail. This option does not affect RTCM generation. The output will be exactly the same as if the RTCMRULE 6 option was chosen. The upper two bits are always encoded as per RTCM specification. 6 is for 6 bits of valid data per byte 8 is for 8 bits of valid data per byte Default 6CR Example: rtcmrule 6cr RTCM16T This is a NovAtel GPSCard command which relates to the RTCM Type 16 This command allows the GPSCard user to set an ASCII text string. Once set, the text string can be transmitted as standard format RTCM Type 16 data (see the RTCM16 command, Appendix C). The text string entered is limited to a maximum of 90 ASCII characters. This message is useful for a reference station wanting to transmit special messages to remote users. The text string set here can be verified by observing the RCCA command configuration log. As well, the message 38 MiLLennium Command Descriptions Manual 6 Message Formats text can be transmitted as a NovAtel Format ASCII log by utilizing the "LOG port RTCM16T" command. Syntax: RTCM16T message Syntax RTCM16T message Range Value up to 90 characters Description Command ASCII text message Example: rtcm16t This is a test of the RTCM16T Special Message. RTCM Standard Logs The NovAtel logs which implement the RTCM Standard Format for Type 1, 3, 9, and 16 messages are known as the RTCM1 (or RTCM), RTCM3, RTCM9, and RTCM16 logs, respectively, while Type 59N-0 messages are listed in the RTCM59 log . NovAtel has created ASCII and binary versions of each of these logs so that RTCM data can be sent or received along with other NovAtel ASCII and binary data over a common communications port. As per the usual convention, an “A” at the end of the log name denotes the NovAtel ASCII version (e.g. RTCM1A), and a “B” denotes the NovAtel binary version (e.g. RTCM1B). These logs contain the same data that is available in the corresponding RTCM Standard Format messages; however, the data has been “packaged” into NovAtel-format messages. These NovAtel-format logs are not in pure RTCM SC-104 format and are not directly usable as such. There are two scenarios which affect how these logs are processed: Case 1: ASCII messages (RTCMxA) • The NovAtel header ($RTCMx) and checksum terminator (*yz) must be stripped off at the receiving end; then, the data will need to be converted from hexadecimal to binary before the RTCM information can be retrieved. • Provided that the GPSCard that is acting as a remote station has its ACCEPT command set to “ACCEPT port COMMANDS” (which is the default setting), the receiving GPSCard will recognize the NovAtel header ($RTCMxA) as a special data input command, and apply the differential corrections data directly. No extra processing is required. Case 2: Binary messages (RTCMxB) • The 12-byte NovAtel header must be stripped off before the RTCM information can be retrieved. • These binary messages are not presently decoded directly by GPSCards, unlike the ASCII messages. MiLLennium Command Descriptions Manual 39 6 Message Formats ASCII The format of the NovAtel ASCII version of an RTCM log is as follows: Structure: header rtcm data Field # *xx Field Type 1 2 header rtcm data 3 4 *xx [CR][LF] [CR][LF] Data Description Example NovAtel format ASCII header hexadecimal representation of binaryformat RTCM SC104 data Checksum Sentence terminator $RTCM3 597E7C7F7B76537A66406F49487F79 7B627A7A5978634E6E7C5155444946 *68 [CR][LF] Example: $RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C515544494 6*68[CR][LF] BINARY The format of the NovAtel binary version of an RTCM log is as follows: Field # Data 1 (header) Sync Checksum Message ID Message byte count RTCM SC104 data 2 Bytes 3 1 4 4 variable Format char char integer integer Offset 0 3 4 8 12 RTCM OR RTCM1 This is the primary RTCM log used for pseudorange differential corrections. This log follows RTCM Standard Format for Type 1 messages. It contains the pseudorange differential correction data computed by the reference station generating this Type 1 log. The log is of variable length, depending on the number of satellites visible and pseudoranges corrected by the reference station. Satellite specific data begins at word 3 of the message. Structure: (Follows RTCM Standard for Type 1 message) Type 1 messages contain the following information for each satellite in view at the reference station: • Satellite ID • Pseudorange correction • Range-rate correction • Issue of Data (IOD) When operating as a reference station, the GPSCard must be in FIX POSITION mode before the data can be correctly logged. When operating as a remote station, the GPSCard command set to "ACCEPT port RTCM". COM port receiving the RTCM data must have its ACCEPT REMEMBER: Upon a change in ephemeris, GPSCard reference stations will transmit Type 1 messages based on the old ephemeris for a period of time defined by the DGPSTIMEOUT command. After the timeout, the reference station will begin to transmit the Type 1 messages based on new ephemeris. 40 MiLLennium Command Descriptions Manual 6 Message Formats RTCMA or RTCM1A This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in ASCII hexadecimal, utilizing a NovAtel header and terminates with a checksum. This message was designed so that RTCM data can be intermixed with other NovAtel ASCII data over a common communications port. The log is not in pure RTCM SC104 format. The header ($RTCM) and terminator (*xx) must be stripped off at the receiving end, then the data will need to be converted from hexadecimal to binary before the RTCM information is retrieved. The RTCM data is further defined by the RTCM rule (see the RTCMRULE command). The RTCMA log can be directly decoded by other NovAtel GPSCard receivers operating as remote stations. They will recognize the $RTCM header as a special data input command and the differential corrections data will be directly applied. The GPSCard remote station receiving this log must have the ACCEPT command set to "ACCEPT port COMMANDS". Structure: $RTCM Field # rtcm data *xx Field Type [CR][LF] Data Description Example 1 2 $RTCM rtcm data NovAtel format ASCII header hexadecimal representation of binary format RTCM SC104 data 3 4 *xx [CR][LF] Checksum Sentence terminator $RTCM 664142406B61455F565F7140607E5D526A5366C7 C7F6F5A5B766D587D7F535C4B697F54594060685 652625842707F77555B766558767F715B7746656B *54 [CR][LF] Example: $RTCM,664142406B61455F565F7140607E5D526A5366C7C7F6F5A5B766D587D7F535C4B697F54594 060685652625842707F77555B766558767F715B7746656B*54[CR][LF] RTCMB or RTCM1B This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in NovAtel Binary Format, utilizing a NovAtel binary header. This message was designed so that RTCM data can be transmitted intermixed with other NovAtel binary data over a common communications port. The log is not in pure RTCM SC104 format and is not directly usable as such. GPSCard remote receivers cannot decode or interpret the RTCMB data (however, the GPSCard can directly interpret RTCM and RTCMA). The 12 byte NovAtel binary header must be stripped off before the RTCM information can be retrieved. The RTCM data is further defined by the RTCM rule (see the RTCMRULE command). REMEMBER: Format: Field # 1 (header) 2 Ensure that the RTCM rule is the same between all equipment. Message ID = 10 Data Sync Checksum Message ID Message byte count RTCM SC104 data Message byte count = variable Bytes 3 1 4 4 variable Format char char integer integer Offset 0 3 4 8 12 RTCM1A Example: $RTCM,597E7D7F716F745A647D7E42405273505276777C7F736C514E7D477A7F7F 5A7E6E62675F406C567F6753725B675F7B436A646A7D787F675D4A505056687C6B MiLLennium Command Descriptions Manual 41 6 Message Formats 567C7F5B69796F40547F73595557555546*51[CR][LF] RTCM1B Message ID = 10 RTCM3 Message byte count = variable REFERENCE STATION PARAMETERS RTK This log contains the GPS position of the reference station expressed in rectangular ECEF coordinates based on the center of the WGS84 ellipsoid. This log uses four RTCM data words following the two-word header, for a total frame length of six 30 bit words (180 bits maximum). Structure: (Follows the RTCM SC-104 Standard for a Type 3 message) Type 3 messages contain the following information: • • • • Scale factor ECEF X-coordinate ECEF Y-coordinate ECEF Z-coordinate The GPSCard only transmits the RTCM Type 3 message (RTCM3) when operating as a reference station paired with GPSCard remote receivers operating in RT-20 Carrier Phase Mode. (See Appendix A for more information.) NOTE: This log is intended for use when operating in RT-20 mode. Example: $RTCM3,597E7C7F7B76537A66406F49487F797B627A7A5978634E6E7C5155444946*68[CR][LF] RTCM3B Message ID = 41 Message byte count = 35 if RTCMRULE = 8 (12 bytes header, 23 bytes data) = 42 if RTCMRULE = 6 (12 bytes header, 30 bytes data) RTCM9 PARTIAL SATELLITE SET DIFFERENTIAL CORRECTIONS RTCM Type 9 messages follow the same format as Type 1 messages. However, unlike Type 1 messages, Type 9’s do not require a complete satellite set. This allows for much faster differential correction data updates to the remote stations, thus improving performance and reducing latency. Type 9 messages should give better performance when SA rate correction variations are high, or with slow or noisy data links. NOTE: The reference station transmitting the Type 9 corrections must be operating with a high-stability clock to prevent degradation of navigation accuracy due to the unmodelled clock drift that can occur between Type 9 messages. NovAtel recommends a high-stability clock such as the PIEZO Model 2900082 whose 2-sample (Allan) variance meets the following stability requirements: 3.24 x 10-24 s2/s2 between 0.5 - 2.0 seconds, and 1.69 x 10-22 T s2/s2 between 2.0 - 100.0 seconds An external clock such as an OCXO requires approximately 10 minutes to warm up and become fully stabilized after power is applied; do not broadcast RTCM Type 9 corrections during this warm-up period. Structure: (Follows 42 the RTCM Standard SC-104 for a Type 1 message) MiLLennium Command Descriptions Manual 6 Message Formats Type 9 messages contain the following information for a group of three satellites in view at the reference station: • Scale factor • User Differential Range Error • Satellite ID • Pseudorange correction • Range-rate correction • Issue of Data (IOD) RTCM9A Example: $RTCM9,66516277547C71435D797760704260596876655F7743585D547562716D7 57E686C5258*6D[CR][LF] RTCM9B Message ID = 42 RTCM16 Message byte count = variable SPECIAL MESSAGE This log contains a special ASCII message that can be displayed on a printer or cathode ray tube. The GPSCard reference station wishing to log this message out to remote stations must use the RTCM16T command to set the required ASCII text message. Once set, the message can then be issued at the required intervals with the “LOG port RTCM16 interval” command. If it is desired that only updated text messages be transmitted, then the GPSCard log interval must be either “onnew” or “onchanged”. The Special Message setting can be verified in the RCCA configuration log. The RTCM16 data log follows the RTCM Standard Format. Words 1 and 2 contain RTCM header information followed by words 3 to n (where n is variable from 3 to 32) which contain the special message ASCII text. Up to 90 ASCII characters can be sent with each RTCM Type 16 message frame. Structure: (Follows the RTCM Standard SC-104 for a Type 16 message) RTCM16A This message is the hexadecimal code equivalent of the special message entered using the RTCM16T command. Example: $RTCM16,6649404045495E5A5C406A58696D76596D5F665F765869694D4E53604D 70696552567E7B675762747B67576C574E596F59697146555A75516F5F667D4967 5656574E53604D55565A6D69647B67777E454659685D56465A67616E4B7E7F7F7D *52[CR][LF] RTCM16B This message is the binary code equivalent of the special message entered using the RTCM16T command. Message ID = 43 Message byte count = variable RTCM16T This message is used at the remote station to report the contents of a Type 16 message that was received from the reference station. Structure: $RTCM16T ASCII Special Message of up to 90 characters *xx [CR][LF] Example: $RTCM16T,Time flies like an arrow; fruit flies like a banana.*1F[CR][LF] MiLLennium Command Descriptions Manual 43 6 Message Formats RTCM59 TYPE 59N-0 NOVATEL PROPRIETARY MESSAGE RTK RTCM Type 59 messages are reserved for proprietary use by RTCM reference station operators. Each message is variable in length, limited only by the RTCM maximum of 990 data bits (33 words maximum). The first eight bits in the third word (the word immediately following the header) serve as the message identification code, in the event that the reference station operator wishes to have multiple Type 59 messages. NovAtel has defined only a Type 59N-0 message to date; it is to be used for operation in GPSCard receivers capable of operating in RT-20 Carrier Phase Differential Positioning Mode. This log is primarily used by a GPSCard reference station to broadcast its RT-20 observation data (delta pseudorange and accumulated Doppler range) to remote RT-20 – capable GPSCard receivers. NOTE 1: The CDSA/B log is very useful for monitoring the serial data link, as well as differential data decode success. NOTE 2: This log is intended for use when operating in RT-20 mode. RTCM59A Example: $RTCM59,665D43406E76576561674D7E7748775843757D4E646B545365647B7F48 657F504D4D6D425B657D5858606B617A737F7F7F464440727D7156577C65494F4D 4A60497F414D7E4272786D55534362406144705D764D596A7340654B6D5B464375 5848597C52705779466C*57[CR][LF] RTCM59B Message ID = 44 Message byte count = variable RTCM RECEIVE ONLY DATA The following RTCM data types can be received and decoded by the GPSCard, however these log types are no longer transmitted. RTCM TYPE 2 Quite often a reference station may have new ephemeris data before remote stations have collected the newer ephemeris. The purpose of Type 2 messages is to act as a bridge between old and new ephemeris data. A reference station will transmit this Type 2 bridge data concurrently with Type 1’s for a few minutes following receipt of a new ephemeris. The remote station adds the Type 2 data (delta of old ephemeris minus new ephemeris) to the Type 1 message data (new ephemeris) to calculate the correct pseudorange corrections (based on the old ephemeris). Once the remote receiver has collected its own updated ephemeris, it will no longer utilize the Type 2 messages. The GPSCard will accept and decode RTCM Standard Type 2 messages, when available and if required. However, the GPSCard no longer transmits Type 2 messages. Type 2 messages are variable in length, depending on the number of satellites being tracked by the reference station. 44 MiLLennium Command Descriptions Manual 7 Rinex-Standard Commands & Logs 7 RINEX-STANDARD COMMANDS & LOGS 7 RINEX-STANDARD COMMANDS & LOGS The Receiver-Independent Exchange (RINEX) format is a broadly-accepted, receiver-independent format for storing GPS data. It features a non-proprietary ASCII file format that can be used to combine or process data generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990; subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types. Each of the file types consists of a header section and a data section, and includes the following information:3 • • • observation files (carrier-phase measurements; pseudorange / code measurements; times of observations) broadcast navigation message files (orbit data for the satellites tracked; satellite clock parameters; satellite health condition; expected accuracy of pseudorange measurements; parameters of single-frequency ionospheric delay model; correction terms relating GPS time to UTC) meteorological data files (barometric pressure; dry air temperature; relative humidity; zenith wet tropospheric path delay; time tags) NOTE: Although RINEX is intended to be a receiver-independent format, there are many optional records and fields. Please keep this in mind when combining NovAtel and non-NovAtel RINEX data. In support of the first two file types, NovAtel has created six ASCII log types that contain data records in RINEX format (XOBS, XOHD, XNAV, XNHD, XKIN, and XSTA). A seventh pseudo-log type (RINEX) can be used instead to simplify data collection. These logs produce multiple lines of output; each line ends with a NovAtel checksum. Once collected these logs should be processed into the 2 standard RINEX files using NovAtel’s Convert utility. A sample session, illustrating the use of the commands and logs, would be as follows: COM1> log com2 rinex ontime 30 (some time later - move to a new site) COM1> log com2 xkin COM1> rinex markernum 980.1.35 COM1> rinex antdh 3.1 (at new site) COM1> log com2 xsta (some time later - logging complete) COM1> unlogall It should be noted that the first line of this example is equivalent to these two lines: COM1> log com2 xobs ontime 30 COM1> log com2 xnav onchanged The use of the pseudo-log RINEX is for convenience only. After the UNLOGALL command, the XNHD and XOHD logs are automatically generated if XNAV and XOHD, respectively, were active. 3. For further information on RINEX Version 2 file descriptions, you may wish to consult relevant articles in scientific journals such as: Gurtner, W., G. Mader (1990): “Receiver Independent Exchange Format Version 2.” CSTG GPS Bulletin Vol. 3 No. 3, Sept/ Oct 1990, National Geodetic Survey, Rockville. MiLLennium Command Descriptions Manual 45 7 Rinex-Standard Commands & Logs 7.1 COMMANDS RINEX This command is used to configure the user-defined fields in the file headers. The settings of all these fields are visible in the RCCA log. All settings can be saved to non-volatile memory on a MiLLennium card by the SAVECONFIG command. A CRESET command will empty all text fields and reduce to zero the antenna offsets. Syntax: RINEX Command RINEX cfgtype cfgtype Range Values AGENCY ANTDE ANTDH ANTDN ANTNUM ANTTYPE COMMENT MARKNAME MARKERNUM OBSERVER RECNUM Description Command Define agency name in observation log header Define antenna delta east (offset to marker) in observation log and static event log Define antenna delta height (offset to marker) in observation log and static event log Define antenna delta north (offset to marker) in observation log and static event log Define antenna number in observation log header Define antenna type in observation log header Add comment to navigation and observation log headers (optional) Define marker name in observation log and static event log Define marker number in observation log (optional) and static event log Define observer name in observation log header Define receiver number in observation log header Command example: COM1> rinex agency NovAtel Surveying Service Ltd. COM1> rinex antde -0.05 COM1> rinex antdh 2.7 COM1> rinex antdn 0.1 COM1> rinex antnum Field #1 COM1> rinex anttype NovAtel 501 COM1> rinex comment Field trial of new receiver COM1> rinex markname A980 COM1> rinex markernum 980.1.34 COM1> rinex observer S.C. Lewis COM1> rinex recnum LGN94100019 COM1> log com1 rcca Log example: $RCCA,COM1,9600,N,8,1,N,OFF,OFF*65 ... etc.... $RCCA,RINEX,COMMENT,Field trial of new receiver*68 $RCCA,RINEX,AGENCY,NovAtel Surveying Service Ltd.*5A $RCCA,RINEX,MARKNAME,A980*15 $RCCA,RINEX,MARKERNUM,980.1.34*24 $RCCA,RINEX,OBSERVER,S.C. Lewis*0B $RCCA,RINEX,RECNUM,LGN94100019*34 $RCCA,RINEX,ANTNUM,Field #1*0A $RCCA,RINEX,ANTTYPE,NovAtel 501*4B $RCCA,RINEX,ANTDN,0.100*09 $RCCA,RINEX,ANTDE,-0.050*2B $RCCA,RINEX,ANTDH,2.700*0B 46 MiLLennium Command Descriptions Manual 7 Rinex-Standard Commands & Logs Note that the RCCA log shows any non-default RINEX settings. 7.2 LOGS RINEX Observation and Navigation Logs and Headers This pseudo - log type exists to simplify the commands for the user. For example, at the command COM1> log com2 rinex ontime 30 the XOBS and XNAV logs are both started. When it is time to cease data collection, the command COM1> unlog com2 rinex or COM1> unlogall will stop the XOBS and XNAV logs, and the XNHD and XOHD logs will be generated once. XKIN Observation Kinematic Event This log generates a time tag and flag to indicate when antenna motion begins. Command example: COM1> log com2 xkin Log example: $XOBS, 96 04 10 17 25 19.5000000 2*00 $XOBS, $XOBS, 4 *** KINEMATIC DATA FOLLOWS *** XNAV 1*2F COMMENT*50 Navigation Data Record This log type contains broadcast navigation message records for each satellite being used. Each set of records consists of: • orbit data for the satellites tracked • satellite clock parameters • satellite health condition • expected accuracy of pseudorange measurements • parameters of single-frequency ionospheric delay model • correction terms relating GPS time to UTC Command example: COM1> log com2 xnav onchanged Log example: $XNAV,22 96 04 10 18 00 0.0 .2988767810166D-03 .2842170943040D-11 .0000000000000D+00*77 $XNAV,.1570000000000D+03 .5162500000000D+02 .4851987819054D-08 -.307153354042D+01*10 $XNAV,.2656131982803D-05.8917320519686D-02.9054318070412D-05 .5153725172043D+04*01 $XNAV, .3240000000000D+06 -.149011611938D-06 .1649994199967D+01 $XNAV,.9465553285374D+00 .1992812500000D+03 .4627841719040D-01 -.806355016494D-08*17 $XNAV,-.175721605224D-09 .1000000000000D+01 .8480000000000D+03 .0000000000000D+00*18 $XNAV,.7000000000000D+01 .0000000000000D+00 .1396983861923D-08 .1117587089539D-07*1E .4130000000000D+03*08 $XNAV,.3170760000000D+06*5E MiLLennium Command Descriptions Manual 47 7 Rinex-Standard Commands & Logs XNHD Navigation Header This log consists of a RINEX-format header for broadcast navigation message files. It can be generated at any point, using a command such as COM1> log com2 xnhd or it will be generated automatically when logging is complete, using a command such as COM1> unlogall Log example: $XNHD, 2 NAVIGATION DATA $XNHD, NovAtel GPSCard NATIVE 96-04-10 16:13 $XNHD,Field trial of new receiver $XNHD,.10245D-07 .14901D-07 $XNHD,.88064D+05 .32768D+05 $XNHD, .9313225746155D-09 $XNHD, RINEX VERSION / TYPE*3B PGM / RUN BY / DATE*05 COMMENT*29 -.5960D-07 -.1192D-06 ION ALPHA*05 -.1966D+06 -.1966D+06 ION BETA*46 -.799360577730D-14 11 503808 848 DELTA-UTC: A0,A1,T,W*3C LEAP SECONDS*4D $XNHD, END OF HEADER*6F XOBS Observation Data Record This log contains observation records, which include the following information: • Times of observations • Carrier-phase measurements • Pseudorange (code) measurements • Doppler measurements A set of observation records is generated at the end of every time interval specified. Command example: COM1> log com2 xobs ontime 5 Log example: $XOBS, 96 04 10 16 12 45.0000000 0 10G22G29G 3G28G16G27G 2G18G31G19*2B $XOBS, 25589487.514 1 134473357.195 11 3689.020 1*20 $XOBS, 24031521.036 7 126285967.262 7 3673.582 7*3E $XOBS, 22439789.377 9 117921029.600 9 270.081 9*2A $XOBS, 22766999.777 9 119640447.360 9 924.831 9*28 $XOBS, 23387648.507 6 122901958.756 6 -640.482 6*2F $XOBS, 21889019.606 8 115027300.270 8 -2682.420 8*3D $XOBS, 24678340.269 7 129684455.444 7 -3295.920 7*3D $XOBS, 21218703.216 9 111503905.438 9 2528.269 9*30 $XOBS, 21855014.913 9 114847991.342 9 -1951.670 9*33 $XOBS, 20157467.672 9 105927196.398 9 -688.169 9*2B XOHD Observation Header This log consists of a RINEX-format header for observation message files. It can be generated at any point, using a command such as COM1> log com2 xohd or it will be generated automatically when logging is complete, using a command such as COM1> unlogall 48 MiLLennium Command Descriptions Manual 7 Rinex-Standard Commands & Logs Log example: $XOHD, 2 OBSERVATION DATA G (GPS) $XOHD,NovAtel GPSCard NATIVE 96-04-10 16:04 $XOHD,Field trial of new receiver $XOHD,A980 $XOHD,980.1.34 $XOHD,S.C. Lewis NovAtel Surveying Service Ltd. $XOHD,LGN94100019 GPSCard-2 FRASER 3.41RC12 $XOHD,Field #1 NovAtel 501 $XOHD, -1634937.3828 -3664677.1214 4942285.1723 $XOHD, 2.7000 0.0500 0.1000 $XOHD, 1 0 7 G 2 G 3 G16 G18 G19 G22 G27 $XOHD, 1 0 3 G28 G29 G31 $XOHD, 3 C1 L1 D1 $XOHD, 5 $XOHD, 1996 4 10 16 4 43.150000 $XOHD, 1996 4 10 16 13 0.000000 $XOHD, 10 $XOHD, G 2 101 101 101 $XOHD, G 3 101 101 101 $XOHD, G16 101 101 101 $XOHD, G18 101 101 101 $XOHD, G19 101 101 101 $XOHD, G22 101 101 101 $XOHD, G27 101 101 101 $XOHD, G28 101 101 101 $XOHD, G29 101 101 101 $XOHD, G31 101 101 101 $XOHD, XSTA RINEX VERSION / TYPE*50 PGM / RUN BY / DATE*02 COMMENT*08 MARKER NAME*62 MARKER number*11 OBSERVER / AGENCY*49 REC # / TYPE / VERS*5F ANT # / TYPE*77 APPROX POSITION XYZ*67 ANTENNA: DELTA H/E/N*56 WAVELENGTH FACT L1/2*2D WAVELENGTH FACT L1/2*28 # / TYPES OF OBSERV*0F INTERVAL*3D TIME OF FIRST OBS*03 TIME OF LAST OBS*56 # OF SATELLITES*14 PRN / # OF OBS*45 PRN / # OF OBS*44 PRN / # OF OBS*50 PRN / # OF OBS*5E PRN / # OF OBS*5F PRN / # OF OBS*57 PRN / # OF OBS*52 PRN / # OF OBS*5D PRN / # OF OBS*5C PRN / # OF OBS*55 END OF HEADER*6E Observation Static Event This log generates a time tag and flag when a new site occupation begins. Command example: COM1> log com2 xsta Log example: $XOBS, 96 04 10 17 25 45.0000000 3 4*39 $XOBS,A980 MARKER NAME*7F $XOBS,980.1.35 $XOBS, $XOBS, MARKER number*0D 3.1000 0.0500 *** NEW SITE OCCUPATION *** MiLLennium Command Descriptions Manual 0.1000 ANTENNA: DELTA H/E/N*4C COMMENT*19 49 A GPS Overview A GPS OVERVIEW A GPS OVERVIEW The Global Positioning System (GPS) is a satellite navigation system capable of providing a highly accurate, continuous global navigation service independent of other positioning aids. GPS provides 24-hour, all-weather, worldwide coverage with position, velocity and timing information. The system uses the NAVSTAR (NAVigation Satellite Timing And Ranging) satellites which consists of 24 operational satellites to provide a GPS receiver with a six to twelve-satellite coverage at all times depending on the model. A minimum of four satellites in view allows the GPSCard to compute its current latitude, longitude, altitude with reference to mean sea level and the GPS system time. Figure A-1 NAVSTAR Satellite Orbit Arrangement A.1 GPS SYSTEM DESIGN The GPS system design consists of three parts: 50 • The Space segment • The Control segment • The User segment MiLLennium Command Descriptions Manual A GPS Overview All these parts operate together to provide accurate three dimensional positioning, timing and velocity data to users worldwide. The Space Segment The space segment is composed of the NAVSTAR GPS satellites. The final constellation of the system consists of 24 satellites in six 55° orbital planes, with four satellites in each plane. The orbit period of each satellite is approximately 12 hours at an altitude of 10,898 nautical miles. This provides a GPS receiver with six to twelve satellites in view from any point on earth, at any particular time. The GPS satellite signal identifies the satellite and provides the positioning, timing, ranging data, satellite status and the corrected ephemerides (orbit parameters) of the satellite to the users. The satellites can be identified either by the Space Vehicle Number (SVN) or the Pseudorandom Code Number (PRN). The PRN is used by the NovAtel GPSCard. The GPS satellites transmit on two L-band frequencies; one centred at 1575.42 MHz (L1) and the other at 1227.60 MHz (L2). The L1 carrier is modulated by the C/A code (Coarse/Acquisition) and the P code (Precision) which is encrypted for military and other authorized users. The L2 carrier is modulated only with the P code. The Control Segment The control segment consists of a master control station, five reference stations and three data up-loading stations in locations all around the globe. The reference stations track and monitor the satellites via their broadcast signals. The broadcast signals contain the ephemeris data of the satellites, the ranging signals, the clock data and the almanac data. These signals are passed to the master control station where the ephemerides are re-computed. The resulting ephemerides corrections and timing corrections are transmitted back to the satellites via the data up-loading stations. The User Segment The user segment, such as the NovAtel GPSCard receiver, consists of equipment which tracks and receives the satellite signals. The user equipment must be capable of simultaneously processing the signals from a minimum of four satellites to obtain accurate position, velocity and timing measurements. A user can also use the data provided by the satellite signals to accomplish specific application requirements. A.2 HEIGHT RELATIONSHIPS What is a geoid? The equipotential surface which best represents mean sea-level where an equipotential surface is any surface where gravity is constant. This surface not only covers the water but is projected throughout the continents. Most surfaces in North America use this surface as its zero value, i.e. all heights are referenced to this surface. What is an ellipsoid? An ellipsoid, also known as a spheroid, is a mathematical surface which is sometimes used to represent the earth. Whenever you see latitudes and longitudes describing the location, this coordinate is being referenced to a specific ellipsoid. GPS positions are referred to an ellipsoid known as WGS84 (World Geodetic System of 1984). What is the relationship between a geoid and an ellipsoid? The relationship between a geoid and an ellipsoid is shown in Figure A-2. MiLLennium Command Descriptions Manual 51 A GPS Overview Figure A-2 Illustration of GPSCard Height Measurements Notes: References: h=H+N N=h-H 1 Topography 2 Geoid (mean sea level) 3 Spheroid (ellipsoid) H = GPSCard computed height above/below geoid N = Geoidal Height (undulation) h = GPS system computed height above the spheroid From the above diagram, and the formula h = H + N, to convert heights between the ellipsoid and geoid we require the geoid-ellipsoid separation value. This value is not easy to determine. A world-wide model is generally used to provide these values. NovAtel GPS receivers store this value internally. This model can also be augmented with local height and gravity information. A more precise geoid model is available from government survey agencies eg. U.S. National Geodetic Survey or Geodetic Survey of Canada (refer to Appendix F, Standards and References). Why is this important for GPS users? The above formula is critical for GPS users as they typically obtain ellipsoid heights and need to convert these into mean sea-level heights. Once this conversion is complete, users can relate their GPS derived heights to more “usable” mean sea-level heights. A.3 GPS POSITIONING GPS positioning can be categorized as follows: 1. single-point or relative 2. static or kinematic 3. real-time or post-mission data processing A distinction should be made between accuracy and precision. Accuracy refers to how close an estimate or measurement is to the true but unknown value; precision refers to how close an estimate is to the mean (average) estimate. Figure A-3 illustrates various relationships between these two parameters: the true value is "located" at the intersection of the cross-hairs, the centre of the shaded area is the "location" of the mean estimate, and the radius of the shaded area is a measure of the uncertainty contained in the estimate. 52 MiLLennium Command Descriptions Manual A GPS Overview Figure A-3 Accuracy versus Precision 4 High accuracy, high precision Low accuracy, high precision High accuracy, low precision Low accuracy, low precision Single-point vs. Relative Positioning In single-point positioning, coordinates of a GPS receiver at an unknown location are sought with respect to the earth's reference frame by using the known positions of GPS satellites being tracked. The position solution generated by the receiver is initially developed in earth-centred coordinates which can subsequently be converted to any other coordinate system. With as few as four GPS satellites in view, the absolute position of the receiver in three-dimensional space can be determined. Only one receiver is needed. With Selective Availability (SA) active, the typical horizontal accuracy obtainable using single-point positioning is of the order of 100 m (95% of the time). In relative positioning, also known as differential positioning, the coordinates of a GPS receiver at an unknown point (the “remote” station) are sought with respect to a GPS receiver at a known point (the “reference” station). The concept is illustrated in Figure A-4. The relative-position accuracy of two receivers locked on the same satellites and not far removed from each other - up to tens of kilometres - is extremely high. The largest error contributors in single-point positioning are those associated with SA and atmospheric-induced effects. These errors, however, are highly correlated for adjacent receivers and hence cancel out in relative measurements. Since the position of the reference station can be determined to a high degree of accuracy using conventional surveying techniques, any differences between its known position and the position computed using GPS techniques can be attributed to various components of error as well as the receiver’s clock bias. Once the estimated clock bias is removed, the remaining error on each pseudorange can be determined. The reference station sends information about each satellite to the remote station, which in turn can determine its position much more exactly than would be possible otherwise. The advantage of relative positioning is that much greater precision (presently as low as 2 mm, depending on the method and environment) can be achieved than by single-point positioning. In order for the observations of the reference station to be integrated with those of the remote station, relative positioning requires either a data link between the two stations (if the positioning is to be achieved in real-time) or else post-processing of the data collected by the remote station. At least four GPS satellites in view are still required. The absolute accuracy of the remote station’s computed position will depend on the accuracy of the reference station’s position. 4. Environment Canada, 1993, Guidelines for the Application of GPS Positioning, p. 22. Minister of Supply and Services Canada MiLLennium Command Descriptions Manual 53 A GPS Overview Figure A-4 Example of Differential Positioning GPS satellites GPS antenna Differential data User with hand-held computer GPS antenna (shown with choke-ring ground plane) Radio RX GPS RX Radio TX GPS RX Remote station Reference station Static vs. Kinematic Positioning Static and kinematic positioning refer to whether a GPS receiver is stationary or in motion while collecting GPS data. Real-time vs. Post-mission Data Processing Real-time or post-mission data processing refer to whether the GPS data collected by the receiver is processed as it is received or after the entire data-collection session is complete. A.3.1 DIFFERENTIAL POSITIONING There are two types of differential positioning algorithms: pseudorange and carrier phase. In both of these approaches, the “quality” of the positioning solution generally increases with the number of satellites which can be simultaneously viewed by both the reference and remote station receivers. As well, the quality of the positioning solution increases if the distribution of satellites in the sky is favourable; this distribution is quantified by a figure of merit, the Position Dilution of Precision (PDOP), which is defined in such a way that the lower the PDOP, the better the solution. Due to the many different applications for differential positioning systems, two types of position solutions are possible. NovAtel’s carrier-phase algorithms can generate both matched and low-latency position solutions, while NovAtel’s pseudorange algorithms generate only low-latency solutions. These are described below: 54 MiLLennium Command Descriptions Manual A GPS Overview 1. The matched position solution is computed at the remote station when the observation information for a given epoch has arrived from the reference station via the data link. Matched observation set pairs are observations by both the reference and remote stations which are matched by time epoch, and contain the same satellites. The matched position solution is the most accurate one available to the operator of the remote station, but it has an inherent latency – the sum of time delays between the moment that the reference station makes an observation and the moment that the differential information is processed at the remote station. This latency depends on the computing speed of the reference station receiver, the rates at which data is transmitted through the various links, and the computing speed of the remote station; the overall delay is of the order of one second. Furthermore, this position cannot be computed any more often than the observations are sent from the reference station. Typically, the update rate is one solution every two seconds. 2. The low latency (or extrapolated) position solution is based on a prediction. Instead of waiting for the observations to arrive from the reference station, a model (based on previous reference station observations) is used to estimate what the observations will be at a given time epoch. These estimated reference station observations are combined with actual measurements taken at the remote station to provide the position solution. Because only the reference station observations are predicted, the remote station’s dynamics will be accurately reflected. The latency in this case (the time delay between the moment that a measurement is made by the remote station and the moment that a position is made available) is determined only by the remote processor’s computational capacity; the overall delay is of the order of 100 ms. Low-latency position solutions can be computed more often than matched position solutions; the update rate can reach 4 solutions per second. The low-latency positions will be provided for data gaps between matched positions of up to 30 seconds (for a carrier-phase solution) or 60 seconds (for a pseudorange solution, unless adjusted using the DGPSTIMEOUT command). A general guideline for the additional error incurred due to the extrapolation process is shown in Table 1-2. A.3.2 PSEUDORANGE ALGORITHMS Pseudorange algorithms correlate the pseudorandom code on the GPS signal received from a particular satellite, with a version generated within the reference station receiver itself. The time delay between the two versions, multiplied by the speed of light, yields the pseudorange (so called because it contains several errors) between the reference station and that particular satellite. The availability of four pseudoranges allows the reference station receiver to compute its position (in three dimensions) and the offset required to synchronize its clock with GPS system time. The discrepancy between the reference station receiver’s computed position and its known position is due to errors and biases on each pseudorange. The reference station receiver sums these errors and biases for each pseudorange, and then broadcasts these corrections to the remote station. The remote receiver applies the corrections to its own measurements; its corrected pseudoranges are then processed in a least-squares algorithm to obtain a position solution. The “wide correlator” receiver design that predominates in the GPS industry yields accuracies of 3-5 m (SEP). NovAtel’s patented Narrow Correlator technology reduces noise and multipath interference errors, yielding accuracies of 1 m (SEP). Pseudorange Differential Positioning GPS SYSTEM ERRORS In general, GPS SPS C/A code single point pseudorange positioning systems are capable of absolute position accuracies of about 100 metres or less. This level of accuracy is really only an estimation, and may vary widely depending on numerous GPS system biases, environmental conditions, as well as the GPS receiver design and engineering quality. There are numerous factors which influence the single point position accuracies of any GPS C/A code receiving system. As the following list will show, a receiver’s performance can vary widely when under the influences of these combined system and environmental biases. MiLLennium Command Descriptions Manual 55 A GPS Overview • Ionospheric Group Delays – The earth’s ionospheric layers cause varying degrees of GPS signal propagation delay. Ionization levels tend to be highest during daylight hours causing propagation delay errors of up to 30 metres, whereas night time levels are much lower and may be up to 6 metres. • Tropospheric Refraction Delays – The earth’s tropospheric layer causes GPS signal propagation delays which bias the range measurements. The amount of delay is at the minimum (about three metres) for satellite signals arriving from 90 degrees above the horizon (overhead), and progressively increases as the angle above the horizon is reduced to zero where delay errors may be as much as 50 metres at the horizon. • Ephemeris Errors – Some degree of error always exists between the broadcast ephemeris’ predicted satellite position and the actual orbit position of the satellites. These errors will directly affect the accuracy of the range measurement. • Satellite Clock Errors – Some degree of error also exists between the actual satellite clock time and the clock time predicted by the broadcast data. This broadcast time error will cause some bias to the pseudorange measurements. • Receiver Clock Errors – Receiver clock error is the time difference between GPS receiver time and true GPS time. All GPS receivers have differing clock offsets from GPS time that vary from receiver to receiver by an unknown amount depending on the oscillator type and quality (TCXO vs. OCXO, etc.). However, because a receiver makes all of its single point pseudorange measurements using the same common clock oscillator, all measurements will be equally offset, and this offset can generally be modelled or quite accurately estimated to effectively cancel the receiver clock offset bias. Thus, in single point positioning, receiver clock offset is not a significant problem. However, in pseudorange differential operation, between-receiver clock offset is a source of uncorrelated bias. • Selective Availability (SA) – Selective availability is when the GPS Control Segment intentionally corrupts satellite clock timing and broadcast orbit data to cause reduced positioning accuracy for general purpose GPS SPS users (non-military). When SA is active, range measurements may be biased by as much as 30 metres. • Multipath Signal Reception – Multipath signal reception can potentially cause large pseudorange and carrier phase measurement biases. Multipath conditions are very much a function of specific antenna site location versus local geography and man-made structural influences. Severe multipath conditions could skew range measurements by as much as 100 metres or more. See Appendix B, Multipath Elimination Technology for more information. The NovAtel GPSCard receivers are capable of absolute single point positioning accuracies of 15 metres CEP (GDOP < 2; no multipath) when SA is off and 40 metres CEP while SA is on. (As the status of selective availability is generally unknown by the real-time GPS user, the positioning accuracy should be considered to be that of when SA is on). The general level of accuracy available from single point operation may be suitable for many types of positioning such as ocean going vessels, general aviation, and recreational vessels that do not require position accuracies of better than 100 metres CEP. However, increasingly more and more applications desire and require a much higher degree of accuracy and position confidence than is possible with single point pseudorange positioning. This is where differential GPS (DGPS) plays a dominant role in higher accuracy real-time positioning systems. SINGLE POINT AVERAGING WITH THE GPSCARD By averaging many GPS measurement epochs over several hours, it is possible to achieve an absolute position based on the WGS 84 datum to better than five meters. This section attempts to explain how the position averaging function operates and to provide an indication of the level of accuracy that can be expected versus total averaging time. The POSAVE command implements position averaging for reference stations. Position averaging will continue for a specified number of hours or until the averaged position is within specified accuracy limits. Averaging will stop when the time limit or the horizontal standard deviation limit or the vertical standard deviation limit is achieved. 56 MiLLennium Command Descriptions Manual A GPS Overview When averaging is complete, the FIX POSITION command will automatically be invoked. If the maximum time is set to 1 hour or larger, positions will be averaged every 10 minutes and the standard deviations reported in the PAVA/B log should be correct. If the maximum time is set to less than 1 hour, positions will be averaged once per minute and the standard deviations reported in the log will likely not be accurate; also, the optional horizontal and vertical standard deviation limits cannot be used. If the maximum time that positions are to be measuered is set to 24, for example, you can then log PAVA with the trigger ‘onchanged’ to see the averaging status. i.e., posave 24 log com1 pava onchanged You could initiate differential logging, then issue the POSAVE command followed by the SAVECONFIG command. This will cause the GPSCard to average positions after every power-on or reset, then invoke the FIX POSITION command to enable it to send differential corrections. The position accuracy that may be achieved by these methods will be dependent on many factors: average satellite geometry, sky visibility at antenna location, satellite health, time of day, etc.. The following graph summarizes the results of several examples of position averaging over different time periods. The intent is to provide an idea of the relationship between averaging time and position accuracy. All experiments were performed using a single frequency receiver with an ideal antenna location, see Figure A-5. Figure A-5 Single Point Averaging WARNING: This graph represents typical results using position averaging. 35 30 Standard Deviation (meters) 25 20 15 10 5 0 0 4 8 12 16 20 24 28 32 36 40 44 48 Time (hours) Latitude Longtitude Height This function is useful for obtaining the WGS84 position of a point to a reasonable accuracy without having to implement differential GPS. It is interesting to note that even a six hour occupation can improve single point GPS accuracy from over fifty meters to better than five meters. This improved accuracy is primarily due to the reductions of the multipath and selective availability errors in the GPS signal. Again, it is necessary to keep in mind that the resulting standard deviations of the position averaging can vary quite a bit, especially over relatively short averaging times. To illustrate, the position averaging function was run for a period of one hour at three different times during the day. The resulting standard deviation in latitude varied from 4.7 to 7.0 meters. Similarly, the variation in longtitude and height were 4.9 to 6.7 meters and 10.9 to 12.5 meters respectively. This degree of variation is common for averaging periods of less than 12 hours due to changes in the satellite constellation. The graph, however, should at least provide some indication of the accuracy one may expect from single point position averaging. MiLLennium Command Descriptions Manual 57 A GPS Overview Dual Station Differential Positioning It is the objective of operating in differential mode to either eliminate or greatly reduce most of the errors introduced by the above types of system biases. Pseudorange differential positioning is quite effective in largely removing most of the biases caused by satellite clock error, ionospheric and tropospheric delays (for baselines less than 50 km), ephemeris prediction errors, and SA. However, the biases caused by multipath reception and receiver clock offset are uncorrelated between receivers and thus cannot be cancelled by "between receiver single differencing" operation. Differential operation requires that stations operate in pairs. Each pair consists of a reference station (or control station) and a remote station. A differential network could also be established when there is more than one remote station linked to a single reference station. In order for the differential pair to be effective, differential positioning requires that both reference and remote station receivers track and collect satellite data simultaneously from common satellites. When the two stations are in relatively close proximity (< 50 km), the pseudorange bias errors are considered to be nearly the same and can be effectively cancelled by the differential corrections. However, if the baseline becomes excessively long, the bias errors begin to decorrelate, thus reducing the accuracy or effectiveness of the differential corrections. Figure A-6 Typical Differential Configuration Radio Data Link GPSAntenna With Chokering Differential Corrections Output Modem GPS Receiver Reference Station 58 Differential Corrections Input Remote Station MiLLennium Command Descriptions Manual A GPS Overview THE REFERENCE STATION The nucleus of the differential network is the reference station. To function as a base station, the GPS receiver antenna must be positioned at a control point whose position is precisely known in the GPS reference frame. Typically, the fixed position will be that of a geodetic marker or a pre-surveyed point of known accuracy. The reference receiver must then be initialized to fix its position to agree with the latitude, longitude, and height of the phase centre of the reference station GPS receiver antenna. Of course, the antenna offset position from the marker must be accurately accounted for. Because the reference station’s position is fixed at a known location, it can now compute the range of its known position to the satellite. The reference station now has two range measurements with which to work: computed pseudoranges based on its known position relative to the satellite, and measured pseudoranges which assumes the receiver position is unknown. Now, the reference station’s measured pseudorange (unknown position) is differenced against the computed range (based on known position) to derive the differential correction which represents the difference between known and unknown solutions for the same antenna. This difference between the two ranges represents the combined pseudorange measurement errors resulting from receiver clock errors, atmospheric delays, satellite clock error, orbital errors, and SA. The reference station will derive pseudorange corrections for each satellite being tracked. These corrections can now be transmitted over a data link to one or more remote stations. It is important to ensure that the reference station’s FIX POSITION setting be as accurate as possible, as any errors here will directly bias the pseudorange corrections computed, and can cause unpredictable results depending on the application and the size of the base station position errors. As well, the reference station’s pseudorange measurements may be biased by multipath reception. THE REMOTE STATION A remote station is generally any receiver whose position is of unknown accuracy, but has ties to a reference station through an established data link. If the remote station is not receiving differential corrections from the reference station, it is essentially utilizing single point positioning measurements for its position solutions, thus is subject to the various GPS system biases. However, when the remote GPS receiver is receiving a pseudorange correction from the reference station, this correction is algebraically summed against the local receiver’s measured pseudorange, thus effectively cancelling the effects of orbital and atmospheric errors (assuming baselines < 50 km), as well as eliminating satellite clock error. The remote must be tracking the same satellites as the reference in order for the corrections to take effect. Thus, only common satellites will utilize the differential corrections. When the remote is able to compute its positions based on pseudorange corrections from the reference station, its position accuracies will approach that of the reference station. Remember, the computed position solutions are always that of the GPS receiving antenna phase centre. A.4 CARRIER-PHASE ALGORITHMS Carrier-phase algorithms monitor the actual carrier wave itself. These algorithms are the ones used in real-time kinematic (RTK) positioning solutions - differential systems in which the remote station, possibly in motion, requires reference-station observation data in real-time. Compared to pseudorange algorithms, much more accurate position solutions can be achieved: carrier-based algorithms can achieve accuracies of 1-2 cm (CEP). A carrier-phase measurement is also referred to as an accumulated delta range (ADR). At the L1 frequency, the wavelength is 19 cm; at L2, it is 24 cm. The instantaneous distance between a GPS satellite and a receiver can be thought of in terms of a number of wavelengths through which the signal has propagated. In general, this number has a fractional component and an integer component (such as 124 567 967.330 cycles), and can be viewed as a pseudorange measurement (in cycles) with an initially unknown constant integer offset. Tracking loops can compute the fractional component and the change in the integer component with relative ease; however, the determination of the initial integer portion is less straight-forward and, in fact, is termed the ambiguity. In contrast to pseudorange algorithms where only corrections are broadcast by the reference station, carrier-phase algorithms typically “double difference” the actual observations of the reference and remote station receivers. Double-differenced observations are those formed by subtracting measurements between identical satellite pairs on two receivers: MiLLennium Command Descriptions Manual 59 A GPS Overview ADRdouble difference = (ADRrx A,sat i - ADRrx A,sat j) - (ADRrx B,sat i - ADRrx B,sat j) An ambiguity value is estimated for each double-difference observation. One satellite is common to every satellite pair; it is called the reference satellite, and it is generally the one with the highest elevation. In this way, if there are n satellites in view by both receivers, then there will be n-1 satellite pairs. The difference between receivers A and B removes the correlated noise effects, and the difference between the different satellites removes each receiver’s clock bias from the solution. In the NovAtel RTK system, a floating (or “continuous-valued”) ambiguity solution is continuously generated from a Kalman filter. When possible, fixed-integer ambiguity solutions are also computed because they are more accurate, and produce more robust standard-deviation estimates. Each possible discrete ambiguity value for an observation defines one lane; that is, each lane corresponds to a possible pseudorange value. There are a large number of possible lane combinations, and a receiver has to analyse each possibility in order to select the correct one. For single-frequency receivers, there is no alternative to this brute-force approach. However, one advantage of being able to make both L1 and L2 measurements is that linear combinations of the measurements made at both frequencies lead to additional values with either “wider” or “narrower” lanes. Fewer and wider lanes make it easier for the software to choose the correct lane, having used the floating solution for initialization. Once the correct wide lane has been selected, the software searches for the correct narrow lane. Thus, the searching process can more rapidly and accurately home in on the correct lane when dual-frequency measurements are available. Changes in the geometry of the satellites aids in ambiguity resolution; this is especially noticeable in L1-only solutions. In summary, NovAtel’s RTK system permits L1/L2 receivers to choose integer lanes while forcing L1only receivers to rely exclusively on the floating ambiguity solution. Once the ambiguities are known, it is possible to solve for the vector from the reference station to the remote station. This baseline vector, when added to the position of the reference station, yields the position of the remote station. In the NovAtel RTK system, the floating ambiguity and the integer position solutions (when both are available) are continuously compared for integrity purposes. The better one is chosen and output in the receiver’s matchedposition logs. The “best” ambiguities determined are used with the remote station’s local observations and a reference station observation model to generate the remote station’s low-latency observations. NovAtel’s RTK product line consists of RT-2 and RT-20 software. Performance characteristics of each are described in Appendix E. 60 MiLLennium Command Descriptions Manual B Multipath Elimination Technology B MULTIPATH ELIMINATION TECHNOLOGY B MULTIPATH ELIMINATION TECHNOLOGY Multipath signal reception is one of the most plaguing problems that detracts from the accuracy potential of GPS pseudorange differential positioning systems. This section will provide a brief look at the problems of multipath reception and some solutions developed by NovAtel. B.1 MULTIPATH Multipath occurs when an RF signal arrives at the receiving antenna from more than one propagation route (multiple propagation paths). Figure B-1 Illustration of GPS Signal Multipath Why Does Multipath Occur? When the GPS signal is emitted from the satellite antenna, the RF signal propagates away from the antenna in many directions. Because the RF signal is emitted in many directions simultaneously and is traveling different paths, these signals encounter various and differing natural and man-made objects along the various propagation routes. Whenever a change in medium is encountered, the signal is either absorbed, attenuated, refracted, or reflected. Refraction and reflection cause the signals to change direction of propagation. This change in path directions often results in a convergence of the direct path signal with one or more of the reflected signals. When the receiving antenna is the point of convergence for these multipath signals, the consequences are generally not favorable. Whenever the signal is refracted, some signal polarity shifting takes place; and when full reflection occurs, full polarity reversal results in the propagating wave. The consequences of signal polarity shifting and reversal at the receiving antenna vary from minor to significant. As well, refracted and reflected signals generally sustain some degree of signal amplitude attenuation. It is generally understood that, in multipath conditions, both the direct and reflected signals are present at the antenna and the multipath signals are lower in amplitude than the direct signal. However, in some situations, the direct signal may be obstructed or greatly attenuated to a level well below that of the received multipath signal. Obstruction of direct path signals is very common in city environments where many tall buildings block the line of sight to the satellites. As buildings generally contain an abundance of metallic materials, GPS signal reflections are abundant (if not overwhelming) in these settings. Obstructions of direct path signals can occur in wilderness settings as well. If the GPS receiver is in a valley with nearby hills, mountains and heavy vegetation, signal MiLLennium Command Descriptions Manual 61 B Multipath Elimination Technology obstruction and attenuation are also very common. Consequences of Multipath Reception Because GPS is a radio ranging and positioning system, it is imperative that ground station signal reception from each satellite be of direct line of sight. This is critical to the accuracy of the ranging measurements. Obviously, anything other than direct line of sight reception will skew and bias the range measurements and thus the positioning triangulation (or more correctly, trilateration). Unfortunately, multipath is almost always present to some degree, due to real world conditions. When a GPS multipath signal converges at the GPS antenna, there are two primary problems that occur: 1. 2. a multiple signal with amplitude and phase shifting, and a multiple signal with differing ranges. When a direct signal and multipath signal are intercepted by the GPS antenna, the two signals will sum according to the phase and amplitude of each. This summation of signals causes the composite to vary greatly in amplitude, depending on the degree of phase shift between the direct signal versus the multipath signal. If the multipath signal lags the direct path signal by less than 90° the composite signal will increase in amplitude (relative to the direct signal, depending on the degree of phase shift between 0° and 90°). As well, if the multipath signal lags the direct path signal by greater than 90° but less than 270° the composite signal will decrease in amplitude. Depending on the relative amplitude of the multipath signal (or signals), the composite signal being processed by the receiver correlator may experience substantial amplitude variations, which can play havoc with the receiver’s automatic gain control circuitry (AGC) as it struggles to maintain constant signal levels for the receiver correlator. A worst case scenario is when the multipath signal experiences a lag of 180° and is near the same strength as the direct path signal – this will cause the multipath signal to almost completely cancel out the direct path signal, resulting in loss of satellite phase lock or even code lock. Because a multipath signal travels a greater distance to arrive at the GPS antenna, the two C/A code correlations are, by varying degrees, displaced in time, which in turn causes distortion in the correlation peak and thus ambiguity errors in the pseudorange (and carrier phase, if applicable) measurements. As mentioned in previous paragraphs, it is possible that the received multipath signal has greater amplitude than the direct path signal. In such a situation the multipath signal becomes the dominant signal and receiver pseudorange errors become significant due to dominant multipath biases and may exceed 150 metres. For single point pseudorange positioning, these occasional levels of error may be tolerable, as the accuracy expectations are at the 40 metre CEP level (using standard correlator). However, for pseudorange single differencing DGPS users, the accuracy expectations are at the one to five metre CEP level (with no multipath). Obviously, multipath biases now become a major consideration in trying to achieve the best possible pseudorange measurements and position accuracy. If a differential reference station is subject to significant multipath conditions, this in turn will bias the range corrections transmitted to the differential remote receiver. And in turn, if the remote receiver also experiences a high level of multipath, the remote receiver position solutions will be significantly biased by multipath from both stations. Thus, when the best possible position solutions are required, multipath is certainly a phenomenon that requires serious consideration. B.2 HARDWARE SOLUTIONS FOR MULTIPATH REDUCTION A few options exist by which GPS users may reduce the level of multipath reception. Among these include: antenna site selection, special antenna design, and ground plane options. Antenna Site Selection Multipath reception is basically a condition caused by environmental circumstances. Some of these conditions you may have a choice about and some you may not. Many GPS reception problems can be reduced, to some degree, by careful antenna site selection. Of primary importance is to place the antenna so that unobstructed line-of-sight reception is possible from horizon to horizon and at all bearings and elevation angles from the antenna. This is, of course, the ideal situation, which may not be 62 MiLLennium Command Descriptions Manual B Multipath Elimination Technology possible under actual operating conditions. Try to place the antenna as far as possible from obvious reflective objects, especially reflective objects that are above the antenna’s radiation pattern horizon. Close-in reflections will be stronger, and typically have a shorter propagation delay allowing for autocorrelation of signals with a propagation delay of less than one C/A code chip (300 metres). Figure B-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height When the antenna is in an environment with obstructions and reflective surfaces in the vicinity, it is advantageous to mount the antenna as high as possible to reduce the obstructions, as well as reception from reflective surfaces, as much as possible. Water bodies are extremely good reflectors of GPS signals. Because of the short wavelengths at GPS frequencies, even small ponds and water puddles can be a strong source of multipath reception, especially for low angle satellites. Thus, it can be concluded that water bodies such as lakes and oceans are among the most troublesome multipath environments for low angle signal reception. Obviously, water body reflections are a constant problem for ocean going vessels. Antenna Designs Low angle reflections, such as from water bodies, can be reduced by careful selection of antenna design. For example, flat plate microstrip patch antennas have relatively poor reception properties at low elevation angles near their radiation pattern horizon. Quadrifilar helix antennas and other similar vertically high profile antennas tend to have high radiation gain patterns at the horizon. These antennas, in general, are more susceptible to the problems resulting from low angle multipath reception. So, for marine vessels, this type of antenna encourages multipath reception. However, the advantages of good low angle reception also means that satellites can be acquired more easily while rising in the horizon. As well, vessels subject to pitch and roll conditions will experience fewer occurrences of satellite loss of lock. A good antenna design will also incorporate some form of left hand circular polarization (LHCP) rejection. Multipath signals change polarization during the refraction and reflection process. This means that generally, multipath signals may be LHCP oriented. This property can be used to advantage by GPS antenna designers. If a GPS antenna is well designed for RHCP polarization, then LHCP multipath signals will automatically be attenuated somewhat during the induction into the antenna. To further enhance performance, antennas can be designed to increase the rejection of LHCP signals. NovAtel’s GPSAntenna model 501 is an example of an antenna optimized to further reject LHCP signals by more than 10 dB. MiLLennium Command Descriptions Manual 63 B Multipath Elimination Technology Figure B-3 Illustration of Quadrifilar vs. Microstrip Patch Antennae Quadrifilar Elements Radome Antenna Patch Dielectric Patch Ground Plane Quadrifilar Helix Antenna Microstrip Patch Antenna Antenna Ground Planes Nearby objects can influence the radiation pattern of an antenna. Thus, one of the roles of the antenna ground plane is to create a stabilizing artificial environment on which the antenna rests and which becomes a part of the antenna structure and its resultant radiation pattern. A small ground plane (relative to one wavelength at the operating frequency) may have minimal stabilizing effect, whereas a large ground plane (multiple wavelengths in size) will have a highly stabilizing effect. Large ground planes also exhibit a shielding effect against RF signal reflections originating below the antenna’s radiation pattern horizon. This can be a very effective low angle shield when the antenna is elevated on a hill or other structure above other reflecting surfaces such as vehicles, railway tracks, soil with high moisture content, water bodies, etc. One of the drawbacks of a "flat plate" ground plane is that they do provide an above horizon reflective surface for low angle GPS signals. This means that the flat plate is also a multipath generating surface. For pseudorange code measurements, these multipath signals are too close to cause any significant range errors. However, for carrier phase measurements, the flat plate can cause significant biases. Even if carrier phase is not being used for range measurements, the flat plate reflections could be substantial enough to cause signal fades and drop-outs due to carrier phase reversals from the flat plate reflections (keeping in mind that these problems are most substantial for low angle signals). It should also be kept in mind that low profile antennas such as the patch antenna will obviously be less susceptible to this phenomenon than higher profile quadrifilar and bifilar helix antennas. The most effective type of multipath reduction ground plane structure is the "choke ring" ground plane. Due to its surface cavity construction, surface reflections are essentially trapped, thus minimizing the problems encountered by flat plate ground planes. This is what makes NovAtel’s GPSAntenna model 501 so successful when used with the NovAtel GPSAntenna Choke Ring Ground Plane. Figure B-4 Example of GPSAntenna on a Flat Plate vs. Choke Ring Ground Plane Flat plate Choke Ring 64 MiLLennium Command Descriptions Manual B Multipath Elimination Technology NovAtel’s Internal Receiver Solutions for Multipath Reduction The multipath antenna hardware solutions described in the previous paragraphs are capable of achieving varying degrees of multipath reception reduction. These options, however, require specific conscious efforts on the part of the GPS user. In many situations, especially kinematic, few (if any) of the above solutions may be effective or even possible to incorporate. By far, the best solutions are those which require little or no special efforts in the field on the part of the GPS user. This is what makes NovAtel’s internal receiver solutions so desirable and practical. NovAtel has placed long term concerted effort into the development of internal receiver solutions and techniques that achieve multipath reduction, all of which are transparent to the GPSCard user. These achievements have led to Narrow Correlator Technology. It utilizes innovative patented correlator delay lock loop (DLL) techniques. As it is beyond the scope of this manual to describe in detail how the correlator techniques achieve the various levels of performance, the following paragraphs will provide highlights of the advantages of this technology. NARROW CORRELATOR TECHNOLOGY NovAtel’s MiLLennium GPSCard receivers achieve a higher level of pseudorange positioning "performance" vs. standard (wide) correlator, by virtue of its celebrated Narrow Correlator technology. By utilizing Narrow Correlator techniques, the MiLLennium GPSCard is capable of pseudorange measurement improvements better than 2:1 when compared to standard correlation techniques. As well, the Narrow Correlator inherently reduces multipath reception (approaching a factor of eight compared to standard correlator) by virtue of its narrower autocorrelation function. Standard correlators are susceptible to substantial multipath biases for C/A code chip delays of up to 1.5 chip, with the most significant C/A code multipath bias errors occurring at about 0.25 and 0.75 chip (approaching 80 m error). On the other hand, the Narrow Correlator multipath susceptibility peaks at about 0.2 chip (about 10 m error) and remains relatively constant out to 0.95 chip, where it rapidly declines to negligible errors after 1.1 chip. While positioning in single point mode, the multipath and ranging improvement benefits of a Narrow Correlator receiver vs. standard correlator are overridden by a multitude of GPS system biases and errors (with or without an antenna choke ring ground plane). In either case, positioning accuracy will be in the order of 40 metres CEP (SA on, no multipath). However, the benefits of the Narrow Correlator become most significant during pseudorange DGPS operation, where the GPS systematic biases are largely cancelled. Receivers operating DGPS with standard correlator technology typically achieve positioning accuracies in the two to five metre CEP range (low multipath environment and using choke ring ground plane), while NovAtel’s Narrow Correlator receivers are able to achieve positioning accuracies in the order of 0.75 metre CEP (low multipath environment and using choke ring ground plane). The Narrow Correlator achieves this higher accuracy through a combination of lower noise ranging measurements combined with its improved multipath resistance when compared to the standard correlator. SUMMARY Any localized propagation delays or multipath signal reception cause biases to the GPS ranging measurements that cannot be differenced by traditional DGPS single or double differencing techniques. Generally speaking, single point positioning systems are not too concerned with multipath reception, as the system errors are quite large to begin with. However, multipath is recognized as the greatest source of errors encountered by a system operating in differential mode. It has been discussed that careful site selection and good antenna design combined with a choke ring ground plane are fairly effective means of reducing multipath reception. Internal receiver solutions for multipath elimination are achieved through various types of correlation techniques, where the "standard correlator" is the reference by which all other techniques can be compared. The Narrow Correlator has a two fold advantage over standard correlators: improved ranging measurements due to a sharper, less noisy correlation peak, and reduced susceptibility to multipath due to rejection of C/A code delays of greater than 1.0 chip. When used with a choke ring ground plane, the Narrow Correlator provides substantial performance gains over standard correlator receivers operating in differential mode. MiLLennium Command Descriptions Manual 65 C Commands Summary C C COMMANDS SUMMARY COMMANDS SUMMARY ACCEPT The ACCEPT command controls the processing of input data and is primarily used to set the GPSCard’s COM port command interpreter for acceptance of various data formats. Each port can be controlled to allow ASCII command processing (default), binary differential data processing, or the command interpreter can be turned off. The command interpreter automatically distinguishes between ASCII commands and certain NovAtel-format ASCII and binary logs without receiving an ACCEPT command. MiLLennium GPSCards will by default interpret $RTCM59A corrections, and will interpret RTCM59 if ACCEPT RTCM has been entered. On certain GPSCards the ACCEPT port COMMANDS mode will by default accept, interpret, and process these data messages: $PVAA, PVAB, $REPA, REPB, $RTCM1A, $RTCAA, $RTCM3A, $RTCM9A, $RTCM16A, $TM1A and TM1B, without any other initialization required. The command interpreter can process some NovAtel-format binary logs (which have a proprietary header) or ASCII logs without receiving an ACCEPT command. Therefore, the ACCEPT command is needed only for the RTCA and RTCM logs. When using ACCEPT RTCM, the interpretation of the RTCM data will follow the rules defined by the RTCMRULE command (see Chapter 6, Message Formats). In the default processing mode (ACCEPT port COMMANDS), input ASCII data received by the specified port will be interpreted and processed as a valid GPSCard command. If the input data cannot be interpreted as a valid GPSCard command, an error message will be echoed from that port (if the command MESSAGES is “ON”). When valid data is accepted and interpreted by the port, it will be processed and acknowledged by echoing the port prompt (with the exception of VERSION and HELP commands, which reply with data before the prompt). In the binary differential data processing modes, (ACCEPT port RTCA/RTCM), only the applicable data types specified will be interpreted and processed by the specified COM port; no other data will be interpreted. It is important to note that only one out of two COM ports can be specified to accept binary differential correction data. Both ports cannot be set to accept differential data at the same time. When ACCEPT port NONE is set, the specified port will be disabled from interpreting any input data. Therefore, no commands or differential corrections will be decoded by the specified port. However, data can still be logged out from the port, and data can be input to the port for formatting into Pass-Through logs (see Chapter 5). If the GPSCard operator wants to time-tag non-GPS messages as a Pass-Through log, it is recommended that the port accepting the Pass-Through data be set to “NONE”. This will prevent the accepting GPSCard COM port from echoing error messages in response to receipt of unrecognized data. If you do not wish to disable the command interpreter, and do want to disable message error reporting, see the MESSAGES command, Appendix C. The GPSCard user can monitor the differential data link as well as the data decoding process by utilizing the CDSA/B logs. See the CDSA/B log, Appendix D for more information on data link monitoring. 66 MiLLennium Command Descriptions Manual C Commands Summary Syntax: ACCEPT Syntax ACCEPT port option (GPSCard model dependent) port option Range Value COM1 or COM2 NONE COMMANDS RTCA RTCM Description Command Specifies the COM port to be controlled Turn off Command Interpreter Command Interpreter attempts to interpret all incoming data. Will also interpret certain ASCII and NovAtel format binary logs. Interprets RTCAB or raw binary RTCA data only (Types 1,7) Interprets raw binary RTCM data only (Types 1,2,3,9,16 and 59N) Default commands Example: accept com1 rtcm MiLLennium Command Descriptions Manual 67 C Commands Summary ANTENNAPOWER On MiLLennium GPSCards this command enables or disables the supply of electrical power from the internal power source of the card to the low-noise amplifier (LNA) of an active antenna. Jumper P301 allows the user to power the LNA either by an internal power source (plug connects pins 1&2) or an optional external power source (plug connects pins 2&3); or, the user can cut off all power to the antenna (plug removed). For more information on these jumper settings, please refer to Chapter 3 of the MiLLennium Guide to Installation and Operation. The ANTENNAPOWER command, which is only relevant when Jumper P301 is set to connect pins 1&2, determines whether or not internal power is applied to pin 1 of Jumper P301. Table C-1 summarizes the combinations: Table C-1 Antenna LNA Power Configuration P301: plug connects pins 1&2 P301: plug connects pins 2&3 P301: no plug internal power connected to LNA no external effect no external effect ANTENNAPOWER = ON internal power cut off from LNA no external effect no external effect ANTENNAPOWER = OFF The setting of this command will affect the way the MiLLennium’s self-test diagnostics (see Table D-5, Appendix D) report the antenna’s status. Syntax: ANTENNAPOWER Command ANTENNAPOWER flag flag Range Value (none) ON OFF Description Command Displays status of the internal antenna-power supply. If plug on P301 joins pins 1&2, connects internal power to the LNA. Antenna status will be reported as “GOOD” unless a fault is detected, in which case the status will change to “BAD” and the internal power cut off from pin 1. If plug on P301 joins pins 1&2, cuts off internal power from the LNA. Antenna status will always be reported as “GOOD”. Default on Example: antennapower off 68 MiLLennium Command Descriptions Manual C Commands Summary ASSIGN This command may be used to aid in the initial acquisition of a satellite by allowing you to override the automatic satellite/channel assignment and reacquisition processes with manual instructions. The command specifies that the indicated tracking channel search for a specified satellite at a specified Doppler frequency within a specified Doppler window. The instruction will remain in effect for the specified channel and PRN, even if the assigned satellite subsequently sets. If the satellite Doppler offset of the assigned channel exceeds that specified by the Search-Window parameter of the ASSIGN command, the satellite may never be acquired or re-acquired. To cancel the effects of ASSIGN, you must issue the UNASSIGN or UNASSIGNALL command, or reboot the GPSCard. When using this command, NovAtel recommends that you monitor the channel tracking status (ETSA/B) of the assigned channel and then use the UNASSIGN or UNASSIGNALL commands to cancel the command once the channel has reached channel state 4, the Phase Lock Loop (PLL) state. See Appendix D, the ETSA/B ASCII log structure and Table D-7 for an explanation of the various channel tracking states. Syntax: ASSIGN channel Syntax prn doppler Range Value ASSIGN channel 0 - 11 prn doppler 1 - 32 -100,000 to 100,000 Hz search-window 0 - 10,000 search-window Description Default Command Desired channel number from 0 to 11 inclusive (channel 0 represents first channel, channel 11 represents twelfth channel) A satellite PRN integer number from 1 to 32 inclusive Current Doppler offset of the satellite Note: Satellite motion, receiver antenna motion and receiver clock frequency error must be included in the calculation for Doppler frequency. Error or uncertainty in the Doppler estimate above in Hz Note: Any positive value from 0 to 10000 will be accepted. Example: 500 implies ± 500 Hz. unassignall Example assign 0 29 0 2000 Example 1: assign 0,29,0,2000 In example 1, the first channel will try to acquire satellite PRN 29 in a range from -2000 Hz to 2000 Hz until the satellite signal has been detected. Example 2: assign 11,28,-250,0 The twelfth channel will try to acquire satellite PRN 28 at -250 Hz only. MiLLennium Command Descriptions Manual 69 C Commands Summary CLOCKADJUST All oscillators have some inherent drift. On the MiLLennium GPSCard, the clock and the PPS strobe have a 50 ns jitter due to the receiver's attempts to keep the clock as close as possible to GPS time. This option is disabled by entering CLOCKADJUST DISABLE. The jitter will vanish, but the unsteered and free-running clock will drift relative to GPS time. CLOCKADJUST must also be disabled if the user wishes to measure the drift rate of the oscillator using the CLKA/B data logs. Note 1: Please note that, when disabled, the range measurement bias errors will continue to accumulate with clock drift. Note 2: This feature is to be used by advanced users only. Syntax: CLOCKADJUST Syntax CLOCKADJUST switch switch Range Value enable or disable Description Command Allows or disallows adjustment to the internal clock Default enable Example: clockadjust disable 70 MiLLennium Command Descriptions Manual C Commands Summary COMn This command permits you to configure the GPSCard COM port's asynchronous drivers. Syntax: COMn bps parity Syntax COMn bps parity databits stopbits handshake echo FIFO databits stopbits Value handshake echo Description n = 1 or 2 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600 or 115,200 N (none), O (odd) or E (even) 7 or 8 1 or 2 N (none), XON (Xon/Xoff) or CTS (CTS/RTS) ON or OFF ON or OFF Specify COM port Specify bit rate Specify parity Specify number of data bits Specify number of stop bits Specify handshaking Specify echo Transmit the First In First Out queue of the GPSCard’s serial port UART. FIFO Default Example 9600 com2 19200 N 8 1 N OFF ON E 7 1 N ON OFF Examples: com2 19200,e,7,1,n,on,off com1 1200,e,8,1,n,on,off Note: Your GPSCard comes configured this way. If you have different parameters you should reconfigure the communication protocol as per requirements. COMn_DTR This command enables versatile control of the DTR handshake line for use with output data logging in conjunction with external devices such as a radio transmitter. The default state for the COM1 or COM2 DTR line is always high. Syntax: COMn_DTR Syntax control Option COMn_DTR control n = 1 or 2 high low toggle active high low variable variable lead tail active [lead] [tail] Description Selects COM1 or COM2 port control is always high control is always low control toggles between high and low (active, lead, and tail fields are TOGGLE options only) data available during high data available during low lead time before data transmission (milliseconds) tail time after data transmission (milliseconds) Default Example high com1_dtr toggle n/a high n/a n/a 300 150 Examples: com1_dtr toggle,high,300,150 com2_dtr toggle,low,200,110 MiLLennium Command Descriptions Manual 71 C Commands Summary OUTPUT DATA DTR Data 150 ms 300 ms lead tail control COMn_RTS This command enables versatile control of the RTS handshake line for use with output data logging in conjunction with external devices such as a radio transmitter. The default state for the COM1 or COM2 RTS line is always high. COMn_RTS will not influence the COMn command handshake control of incoming commands. Syntax: COMn_RTS control Syntax [lead] Option COMn_RTS control n = 1 or 2 high low toggle active high low variable variable lead tail active [tail] Description Default Selects COM1 or COM2 port control is always high control is always low control toggles between high and low (active, lead, and tail fields are TOGGLE options only) data available during high data available during low lead time before data transmission (milliseconds) tail time after data transmission (milliseconds) Example high com1_rts toggle n/a high n/a n/a 200 100 Example: com1_rts toggle,high,200,100 com2_rts toggle,low,250,125 OUTPUT DATA RTS Data 100 ms 200 ms lead tail control 72 MiLLennium Command Descriptions Manual C Commands Summary CONFIG This command switches the channel configuration of the GPSCard between pre-defined configurations. When invoked, this command loads a new satellite channel-configuration and forces the GPSCard to reset. The types of configurations possible are listed by entering this command: HELP CONFIG In some applications, only the standard (default) configuration will be listed in response. configuration of a MiLLennium GPSCard consists of 12 L1/L2 channel pairs. The standard Syntax: CONFIG cfgtype Command CONFIG cfgtype Option (none) configuration name Description Command Displays present channel configuration Loads new configuration, resets GPSCard MiLLennium Command Descriptions Manual Default standard 73 C Commands Summary CRESET Configuration Reset. Resets user configuration to the factory default. After a reset, non volatile memory (NVM) is read for user configuration. This command does not reset the hardware. See the Factory Default Settings example at the beginning of Chapter 2. Syntax: CRESET See also the FRESET and RESET commands. These three commands differ in the following way: RESET - Resets the hardware. Similar to powering the card off and on again. CRESET - Resets user configuration to the factory default. This command does not reset the hardware. FRESET - Completely resets the receiver to a factory state. Anything that was saved to NVM is erased (including Saved Config, Saved Almanac and Channel Config). The hardware is also reset. 74 MiLLennium Command Descriptions Manual C Commands Summary CSMOOTH This command sets the amount of carrier smoothing to be performed on the pseudorange measurements carrier. An input value of 100 corresponds to approximately 100 seconds of smoothing. Upon issuing the command, the locktime for all tracking satellites is reset to zero. From this point each pseudorange smoothing filter is restarted. The user must wait for at least the length of smoothing time for the new smoothing constant to take full effect. 20 seconds is the default smoothing constant used in the GPSCard. The optimum setting for this command is dependent on the user’s application and thus cannot be specified. Syntax: CSMOOTH Syntax L1 time Range Value CSMOOTH L1 time 2 to 1000 [L2 time] 2 to 1000 [L2 time] Description Command L1 carrier smoothing time constant. Value in seconds L2 carrier smoothing time constant. Value in seconds Default 20 Example: csmooth 500 NOTE: The CSMOOTH command should only be used by advanced users of GPS. It may not be suitable for every GPS application. When using CSMOOTH in a differential mode, the same setting should be used at both the reference and remote station. The shorter the carrier smoothing the more noise there will be. If you are at all unsure please call NovAtel Customer Service Department, see the NovAtel information page. MiLLennium Command Descriptions Manual 75 C Commands Summary DATUM This command permits you to select the geodetic datum for operation of the receiver. If not set, the value is defaulted to WGS84. See Table G-2 in Appendix G for a complete listing of all available predefined datums. See the USERDATUM command for user definable datums. The datum you select will cause all position solutions to be based on that datum (except PXYA/B which is always based on WGS84). Syntax: DATUM Syntax DATUM option Datum Option Description any one of 62 predefined datums USER For a complete list of all 62 predefined datums, see Table G-2 in Appendix G. datum tokyo Sets the system datum to Tokyo Default WGS84 User defined datum with parameters specified by the USERDATUM command (Default WGS84) Example: Note: The actual datum name must be entered in this command as listed in the NAME column of Table G-2. Also note that references to datum in the following logs use the GPSCard Datum ID #: MKPA/B, PRTKA/B, POSA/ B and RTKA/B. 76 MiLLennium Command Descriptions Manual C Commands Summary DGPSTIMEOUT This command has a two-fold function: (1) to set the maximum age of differential data that will be accepted when operating as a remote station. Differential data received that is older than the specified time will be ignored. When entering DGPS delay, you can ignore the ephemeris delay field. (2) to set the ephemeris delay when operating as a reference station. The ephemeris delay sets a time value by which the reference station will continue to use the old ephemeris data. A delay of 120 to 300 seconds will typically ensure that the remote stations have collected updated ephemeris. After the delay period is passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay value, you must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference station, DGPS delay will be ignored. Syntax: DGPSTIMEOUT dgps delay Command DGPSTIMEOUT dgps delay ephem delay ephem delay Option min. max. min. max. 2 1000 0 600 Description Default Command Maximum age in seconds 60 Minimum time delay in seconds 120 Example 1 (remote): dgpstimeout 15 Example 2 (reference): dgpstimeout 2,300 NOTES: The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction messages cannot be greater than 22 seconds. Therefore, for RTCA logs, the recommended DGPS delay setting is 22. The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new ephemeris before transmitting differential corrections. This time interval ensures that the remote stations will have received the new ephemeris, and will compute differential positioning based upon the same ephemeris. Therefore, for RTCA logs, the recommended ephemeris delay is 300 seconds. MiLLennium Command Descriptions Manual 77 C Commands Summary DIFF_PROTOCOL Differential Protocol Control NOTE: The DIFF_PROTOCOL command should only be used by advanced users of GPS. Features: 1. A user definable key such that many different types of encoding may be used in the same area without cross talk between the various “channels”. 2. Encodes all correction data following any header specific to the message type. 3. Non-volatile. When the base station card is restarted, the previously selected encoding key is used for all subsequent differential data. 4. The encoding key is not visible by any method of interrogation. Syntax: Syntax DIFF_PROTOCOL Type or DIFF_PROTOCOL DISABLE or DIFF_PROTOCOL Range Value DIFF_PROTOCOL - Description Key Default Command type 1, DISABLE Encoding Algorithm key 0 - FFFFFFFF 32 Bit Encoding key Notes: If no parameters are given to the command, the encoding type value will be reported. The key value is not visible at anytime. The only supported type of encoding is “Type 1”, which will only encode RTCM data with the algorithm described below. The non-volatility of the command is acquired via the SAVECONFIG command. This command stores the current settings in non-volatile memory. All header information necessary for parsing the incoming data stream remains unencoded. RTCM/A/B LOGS The NovAtel log format wrapping of the RTCMA and RTCMB logs remains unencoded and only the raw RTCM data is encoded beginning after the second word of the message. This will leave the entire header unencoded: WORD 1 WORD 2 REMAINING... 78 Preamble Modified Z-Count Encoded data... Message Type (Frame ID) Sequence No. Station ID Length of Frame Parity Parity MiLLennium Command Descriptions Manual C Commands Summary DYNAMICS This command informs the receiver of user dynamics. It is used to optimally tune receiver parameters. Syntax: DYNAMICS user_dynamics Command DYNAMICS user_dynamics Description Command air land foot receiver is an aircraft receiver is in a land vehicle with velocity less than 110 km/h (30m/s) receiver is being carried by a person with velocity less than 11 km/h (3m/s) Default dynamics air Example: dynamics foot MiLLennium Command Descriptions Manual 79 C Commands Summary ECUTOFF This command sets the elevation cut-off angle for usable satellites. The GPSCard will not start tracking a satellite until it rises above the cutoff angle; however, if a satellite being tracked drops below this angle, it will continue to be tracked until the signal is lost. Satellites that are below the cutoff angle will be eliminated from the internal position and clock offset solution computations only. All satellites in view will still be tracked and their data logged; this data may be used in post processing. If there are more satellites in view than there are channels available, the channels which are tracking satellites below the elevation cut-off will be reassigned to any healthy satellites above the cutoff which are not already assigned to a channel. This command permits a negative cutoff angle; it could be used in these situations: • the receiver is at a high altitude, and thus can look below the local horizon • satellites are visible below the horizon due to atmospheric refraction Syntax: ECUTOFF Syntax ECUTOFF angle angle Range Value -90° to +90° Description Default Command Value in degrees (relative to the horizon). -90 Example: ecutoff 5 NOTE 1: When ECUTOFF is set to zero (0), the receiver will track all SVs in view including some within a few degrees below the horizon. NOTE 2: Care must be taken when using ECUTOFF because the information you are tracking from lower elevation satellite signals are going through more atmosphere, for example ionospheric and tropospheric, and therefore being degraded. 80 MiLLennium Command Descriptions Manual C Commands Summary EXTERNALCLOCK Overview The EXTERNALCLOCK and EXTERNALCLOCK FREQUENCY commands allows the MiLLennium GPSCard to operate with an optional external oscillator. The user is able to optimally adjust the clock model parameters of the GPSCard for various types of external clocks. The three-state clock model on GPSCards having access to this command is different from that used on the other GPSCards. NOTE: The EXTERNALCLOCK command will affect the interpretation of the CLKA/B log. There are three steps involved in using an external oscillator: 1. Follow the procedure outlined in your GPSCard’s installation/operation manual for connecting an external oscillator to your GPSCard. 2. For the chosen oscillator type, use the EXTERNALCLOCK FREQUENCY command to select the operating frequency – either 5 MHz or 10 MHz. 3. Using the EXTERNALCLOCK command, select a standard oscillator or define a new one; the effect is to define h0, h-1, and h-2 in the expression for Sy(f) given below. Steps #2 and #3 define certain parameters used in the clock model for the external oscillator Theory An unsteered oscillator can be approximated by a three-state clock model, with two states representing the range bias and range bias rate, and a third state assumed to be a Gauss-Markov (GM) process representing the range bias error generated from satellite clock dither. The third state is included because the Kalman filter assumes an (unmodeled) white input error. The significant correlated errors produced by SA clock dither are obviously not white and the Markov process is an attempt to handle this kind of short-term variation. The internal units of the new clock model’s three states (offset, drift and GM state) are meters, meters per second, and meters. When scaled to time units for the output log, these become seconds, seconds per second, and seconds, respectively. Note that the old units of the third clock state (drift rate) were meters per second per second. The user has control over 3 process noise elements of the linear portion of the clock model. These are the h0, h-1, and h-2 elements of the power law spectral density model used to describe the frequency noise characteristics of oscillators: h– 2 h –1 Sy ( f ) = -------2 + ------- + h 0 + h 1 f + h 2 f f f 2 where f is the sampling frequency and Sy(f) is the clock’s power spectrum. Typically only h0, h-1, and h-2 affect the clock’s Allan variance and the clock model’s process noise elements. Usage Before using an optional external oscillator, several clock model parameters must be set. There are default settings for a voltage-controlled temperature-compensated crystal oscillator (VCTCXO), ovenized crystal oscillator (OCXO), Rubidium and Cesium standard; or, the user may choose to supply customized settings. MiLLennium Command Descriptions Manual 81 C Commands Summary Syntax: EXTERNALCLOCK Command EXTERNALCLOCK option Option disable ocxo rubidium cesium user h0 h-1 h-2 Description Default Revert to the on-board oscillator MiLLennium = VCTCXO Set defaults for ovenized crystal oscillator Set defaults for rubidium oscillator Set defaults for cesium oscillator Define custom values for process noise elements see Table C-2 Example: externalclock user 1.0e-20 1.0e-24 1.0e-28 Table C-2 Default Values of Process Noise Elements Timing Standard VCTCXO OCXO rubidium cesium user (min / max) 82 h0 1.0 e-21 2.51 e-26 1.0 e-23 2.0 e-20 1.0 e-31 ≤ h0 ≤ 1.0 e-18 h-1 1.0 e-20 2.51 e-23 1.0 e-22 7.0 e-23 1.0 e-31 ≤ h-1 ≤ 1.0 e-18 h-2 2.0 e-20 2.51 e-22 1.3 e-26 4.0 e-29 1.0 e-31 ≤ h-2 ≤ 1.0 e-18 MiLLennium Command Descriptions Manual C Commands Summary EXTERNALCLOCK FREQUENCY Please see the Overview and Theory sub-sections under the EXTERNALCLOCK command to understand the steps involved in using an optional external oscillator with a MiLLennium GPSCard. For the chosen oscillator, one must select the clock rate using the EXTERNALCLOCK FREQUENCY command. The MiLLennium GPSCard only accepts a 5 MHz or 10 MHz external input. An internal frequency synthesizer converts this input to 20 MHz, the actual clock rate required by the MiLLennium GPSCard (and that which is generated by its on-board VCTCXO). Syntax: EXTERNALCLOCK FREQUENCY Command EXTERNALCLOCK FREQUENCY clock rate clock rate Range 5 or 10 Description Set clock rate to 5 MHz or 10 MHz (Will not allow values other than 5 or 10) Default 10 Example: externalclock frequency 5 MiLLennium Command Descriptions Manual 83 C Commands Summary FIX HEIGHT This command configures the GPSCard in 2D mode with its height constrained to a given value. The command would be used mainly in marine applications where height in relation to mean sea level may be considered to be approximately constant. The height entered using this command is always referenced to the geoid (mean sea level, see the PRTKA/B log in Chapter 4 and Appendix D) and uses units of metres. The FIX HEIGHT command will override any previous FIX HEIGHT or FIX POSITION command and disables the output of differential corrections. The receiver is capable of receiving and applying differential corrections from a reference station while FIX HEIGHT is in effect. Use the UNFIX command to disable the current FIX command. No special solution status is reported in the POSA/B or PRTKA/B logs for a 2 dimensional solution. This mode is detected by the standard deviation of the height being 0.001m. Syntax: FIX HEIGHT height [auto] Syntax Range Value Description FIX HEIGHT height auto -1,000.0 to 20,000,000.0 Command Height in metres above mean sea level The receiver will automatically fix the height at the last calculated value if the number of satellites available is insufficient for a 3-D solution, to provide a 2-D solution. Height calculation will resume when the number of satellites available returns to 4 or more. The use of the UNFIX command, or a different FIX command will disable the automatic fix height mode. It is disabled by default. Default unfix Example: fix height 4.567 REMEMBER: Any error in the height estimate will cause an error in the position computed of the same order of magnitude or higher. For example, if the user fixed height to zero and the antenna was installed on a 20 metre mast, the position can be expected to be in error by 10 to 60 metres, depending on the geometry of the satellites. This command should only be used when absolutely necessary, i.e., when only three satellites are visible. NOTE: This command only affects pseudorange corrections and solutions, and so has no meaning within the context of RT-2 and RT-20. 84 MiLLennium Command Descriptions Manual C Commands Summary FIX POSITION (RTK) Invoking this command will result in the GPSCard position being held fixed. A computation will be done to solve local clock offset, pseudorange, and pseudorange differential corrections. This mode of operation can be used for time transfer applications where the position is fixed and accurate GPS time output is required (see the CLKA/B and TM1A/B logs, Appendix D for time data). As well, this command must be properly initialized before the GPSCard can operate as a GPS pseudorange reference station. Once initialized, the receiver will compute pseudorange differential corrections for each satellite being tracked. The computed differential corrections can then be output to remote stations by utilizing any of the following GPSCard differential corrections data log formats: RTCM, RTCMA, RTCMB, RTCA, RTCAA or RTCAB. The reference station servicing RT-20 remote receivers must log RTCM3 and RTCM59(N) pseudorange and carrier phase observation data in order for the RT-20 remote receiver to compute double difference carrier phase solutions. The values entered into the FIX POSITION command should reflect the precise position of the reference station antenna phase centre. Any errors in the FIX POSITION coordinates will directly bias the pseudorange corrections calculated by the reference receiver. The GPSCard performs all internal computations based on WGS84 and the datum command is defaulted as such. The datum in which you choose to operate (by changing the DATUM command) will internally be converted to and from WGS84. Therefore, all differential corrections are based on WGS84, regardless of your operating datum. The GPSCard will begin logging differential data while tracking as few as three healthy satellites. See Appendix A for further discussions on differential positioning. The FIX POSITION command will override any previous FIX HEIGHT UNFIX command to disable the FIX POSITION setting. or FIX POSITION command settings. Use the Syntax: FIX POSITION lat lon height station id [RTCM stn health] Syntax Range Value Description Default Example FIX POSITION lat 0 to ± 90.0 (Up to 8 decimal places are shown in the RCCA log but more precision is determined internally) unfix fix position 51.3455323 lon 0 to ± 360.0 (Up to 8 decimal places are shown in the RCCA log but more precision is determined internally) height -1,000 to 20,000,000 station id 0 to 1023 (10 bits) for RTCM output “xxxx” for RTCA output where ”xxxx” are four alphanumeric characters, entered between double quotes 0-7 where 0-5 Specified by user 6 Reference station transmission not monitored 7 Reference station not working Command Latitude (in degrees/decimal degrees) of fixed reference station antenna in current datum. A negative sign implies South latitude. Longitude (in degrees) of fixed reference station antenna in current datum. A negative sign implies West longitude. Height (in metres) above the geoid of reference station in current datum. Specify a reference Station identification number (optional entry) (see SETDGPSID) Specify RTCM reference station health (optional) (This field will only be reported in RTCM message header - word 2.) 6 RTCM reference station health -114.289534 1201.123 1002 0 Example: fix position 51.3455323,-114.289534,1201.123,1002,0 The above example configures the receiver as a reference station with fixed coordinates of: Latitude N 51º 20' 43.9163" (WGS84 or local datum) Longitude W 114º 17' 22.3224" Height above sea level 1201.123 metres Station ID 1002 RTCM health 0 MiLLennium Command Descriptions Manual 85 C Commands Summary FIX VELOCITY This command supports INS (Inertial Navigation System) integration. It accepts ECEF XYZ velocity values in units of metres per second (m/s). This information is only used by the tracking loops of the receiver to aid in reacquisition of satellites after loss of lock, otherwise it is ignored. It is not used in the position solution and velocity calculations. This command is only useful for very high dynamics where expected velocity changes during the signal blockage of more than 100 metres per second can occur. See Figure D-2 for ECEF definitions. The UNFIX command is used to clear the effects of the FIX VELOCITY command. The FIX VELOCITY command will override any previous FIX HEIGHT or FIX POSITION command. Use the UNFIX command to disable the current FIX command. Syntax: FIX VELOCITY Syntax vx vy vz Range Value FIX VELOCITY vx vy vz ±999.99 ±999.99 ±999.99 Description Command X = Antenna Velocity (ECEF) in the X direction [m/s]. Y = Antenna Velocity (ECEF) in the Y direction [m/s]. Z = Antenna Velocity (ECEF) in the Z direction [m/s]. Default unfix Example fix velocity 315 212 150 Example: fix velocity 315,212,150 86 MiLLennium Command Descriptions Manual C Commands Summary FREQUENCY_OUT This command allows the user to specify the frequency of the output pulse train available at the variable frequency (VARF) pin of the I/O strobe connector. This command has no effect on the operation of the GPSCard; it is only provided for user-determined applications. The frequency (in Hertz) is calculated according to formulas which require three input parameters (n,k,p), such that: if k =1 or p =1: VARF = 0 if n =1 and k ≠ 1, p ≠ 1: 20, 000, 000 VARF = ------------------------------ if n ≠ 1, k ≠ 1, p ≠ 1: 20, 000, 000 × ( n – 1 ) VARF = ----------------------------------------------------- k×p n×k×p The possible range of output frequencies is 0 - 5 MHz. As a reference, some n, k and p selections and their corresponding frequency outputs are listed in Table C-3: Table C-3 VARF Range n 1 1024 1 1 2 1 k p 1 65 536 65 536 4000 4 2 1 65 536 65 536 5000 8 2 VARF (Hz) 0 0.004 652 065 0.004 656 612 1 312 500 5 000 000 (Minimum) (Maximum) The resultant waveform is composed of active-high pulses with a repetition rate as defined above, and a jitter of 50 ns. The pulse width has a range of 100 ns - 51.25 µs, and is calculated as follows: pulse width (ns) = (n + 1) * 50 The command has two syntactical forms. One is to define a frequency, and the other is to disable this function. Syntax 1: FREQUENCY_OUT Command FREQUENCY_OUT N K P N K P Range Values Description 1 - 1024 1 - 65,536 1 - 65,536 Command Variable integer Variable integer Variable integer Example: frequency_out 2,4,8 Syntax 2: FREQUENCY_OUT Command FREQUENCY_OUT keyword keyword Range Values disable Description Command The keyword “DISABLE” is the only one defined at this time. MiLLennium Command Descriptions Manual 87 C Commands Summary FRESET This command clears all data which is stored in non-volatile memory. Such data includes the almanac, satellite channel configuration, and any user-specific configurations. The GPSCard is forced to reset and will start up with factory defaults. See also the CRESET, where the differences between these three commands are explained, and RESET commands. Syntax: FRESET 88 MiLLennium Command Descriptions Manual C Commands Summary HELP This command provides you with on-line help. The command, with no options, gives a complete list of the valid system commands. For detailed help on any command, append the optional command name to the HELP command. Syntax: HELP OR: option ? option Syntax HELP (or ?) option Range Value See Figure C-1 Description Entering HELP without an option will list all valid command options. Can be any valid system command. Information about the command entered will be displayed. Example: help dynamics Figure C-1 shows the screen display of the HELP command as it would be seen if you were using NovAtel’s graphical interface program GPSolution. Figure C-2 shows a specific example of the ASSIGN command appended to the HELP command. Figure C-1 HELP Command Screen Display Com1> help ?-Online Command Help ANTENNAPOWER -Antenna Power Control CLOCKADJUST -Adjust 1pps COM2 -Initialize Port 2 COM2_DTR -DTR Control on Port 2 C0M2_RTS -RTS Control on Port 2 CRESET -Factory Config Reset DATUM -Choose a DATUM Type DIFF_PROTOCOL -Diff.. protocol control ECUTOFF -Elevation Cutoff Angle FIX -Set Antenna Coord.. FREQUENCY OUT -Variable Freq. Output LOCKOUT -Lock Out Satellite MAGVAR -Set Magnetic Variation.on POSAVE -Position Averaging RESETHEALTH -Reset PRN Health RESETRT20 -Reset RT20 algorithm RINEX -RINEX( Configuration RTCMRULE -RTCM Bit Rule SAVECONFIG -Save User Config. SENDHEX-Send hex to a port SETHEALTH -Overr.ide PRN Health SETNAV -Set a Destination UNASSIGN -Un-Assign a Channel UNDULATION-Choose Undulation UNLOCKOUT -Restore Satellite UNLOG -Kill a Data Log USERDATUM -User Defined DATUM Com1> ACCEPT -Accept Datatypes ASSIGN -Assign PRN To a Chan. COM1 -Initialize Port 1 COM1_DTR -DTR Control on Port 1 COM1_RTS -RTS Control on Port 1 CONFIG -Configure Satellites CSMOOTH -Carrier Smoothing DGPSTIMEOUT -Max. aye of DGPS data DYNAMICS -Set Dynamics EXTERNALCLOCK -Specify Clock type RESET -Factory Card Reset HELP -Online Command Help LOG -Choose Date Logging MESSAGES -Error Messages On/Off RESET -Hardware Reset RESETHEALTHALL -Reset All PRE Health RTKMODE -Set RTK parameters RTCM16T -Input Type l6 Message SAVEALMA -Save Almanac & ION/UTC SEND -Send string to a port SETDGPSID -Set the Station ID SETL10FFSET -Set Ll PSR Offset SETTIMESYNC -Enable/Disable Timesync UNASSIGNALL -Un-Assign All Channels UNFIX -Remove Recvr. FIX(ed) UNLOCKOUTALL -Select All Satellites UNLOGALL -Kill all Data Logs VERSION -Current Software Vet. Figure C-2 Appended Command Screen Display COM2> help assign ASSIGN Channel_no, PRN, Doppler, Dop_window Assign a prn to a channel where: Channel_no = A channel number from 0-23 PRN = A satellite PRN number from 1-32 Doppler = Current satellite doppler offset (-100000 to +100000 Hz) Dop_window = Uncertainty in doppler estimate (0 to 10000 Hz) COM2> MiLLennium Command Descriptions Manual 89 C Commands Summary LOCKOUT This command will prevent the GPSCard from using a satellite by de-weighting its range in the solution computations. Note that the LOCKOUT command does not prevent the GPSCard from tracking an undesirable satellite. This command must be repeated for each satellite to be locked out. See also the UNLOCKOUT and UNLOCKOUTALL commands. Syntax: LOCKOUT Syntax LOCKOUT prn prn Range Value 1 - 32 Description Default Command A single satellite PRN integer number to be locked out unlockoutall Example: lockout 8 90 MiLLennium Command Descriptions Manual C Commands Summary LOG Many different types of data can be logged using several different methods of triggering the log events. Every log element can be directed to either the COM1 or COM2 ports. If a selected log element is to be directed to all the ports, then separate LOG commands are required to control them. The ONTIME trigger option requires the addition of the period parameter and optionally allows input of the offset parameter. See Chapter 4 and Appendix D for further information and a complete list of ASCII and Binary data log structures. The optional parameter {hold} will prevent a log from being removed when the UNLOGALL command is issued. To remove a log which was invoked using the {hold} parameter requires the specific use of the UNLOG command. The [port] parameter is optional. If [port] is not specified, [port] is defaulted to the port that the command was received on. Syntax: LOG [port] datatype [trigger] [period] [offset] {hold} Example: log com1,posa,ontime,60,1,hold The above example will cause the POSA log to be logged to COM port 1, recurring every 60 seconds, offset by one second, and with the {hold} parameter set so that logging would not be disrupted by the UNLOGALL command. To send a log only one time, the trigger option can be ignored. Example: log com1 posa log posa MiLLennium Command Descriptions Manual 91 C Commands Summary MAGVAR The GPSCard computes directions referenced to True North. Use this command (magnetic variation correction) if you intend to navigate in agreement with magnetic compass bearings. The correction value entered here will cause the "bearing" field of the NAVA/B and GPVTG logs to report bearing in degrees Magnetic. The magnetic variation correction is also reported in the GPRMC log. Syntax: MAGVAR correction Syntax MAGVAR correction Range Value ± 0 - 180 Description Command The magnetic variation correction for the area of navigation in units of degrees. Magnetic bearing = True bearing + Magnetic Variation Correction See Figure C-3. Default 0.000 Example: magvar +15.0 Figure C-3 Illustration of Magnetic Variation & Correction 92 MiLLennium Command Descriptions Manual C Commands Summary MESSAGES The MESSAGES command is used to disable the port prompt and error message reporting from a specified port. This feature can be useful if the port is connected to a modem or other device that responds with data the GPSCard does not recognize. See Chapter 5 for further information on using this command with Special Pass-Through Logs. Syntax: MESSAGES port Syntax MESSAGES port option option Range Value COM1, COM2 or all ON or OFF Description Command Specifies the port being controlled Enable or disable port prompt and error message reporting Default MESSAGES ON Example: messages com1,off MiLLennium Command Descriptions Manual 93 C Commands Summary POSAVE This command implements position averaging for reference stations. Position averaging will continue for a specified number of hours or until the averaged position is within specified accuracy limits. Averaging will stop when the time limit or the horizontal standard deviation limit or the vertical standard deviation limit is achieved. When averaging is complete, the FIX POSITION command will automatically be invoked. If the maximum time is set to 1 hour or larger, positions will be averaged every 10 minutes and the standard deviations reported in the PAVA/B log should be correct. If the maximum time is set to less than 1 hour, positions will be averaged once per minute and the standard deviations reported in the log will likely not be accurate; also, the optional horizontal and vertical standard deviation limits cannot be used. One could initiate differential logging, then issue the POSAVE command followed by the SAVECONFIG command. This will cause the GPSCard to average positions after every power-on or reset, then invoke the FIX POSITION command to enable it to send differential corrections. Syntax: POSAVE maxtime Command maxhorstd maxverstd Range Values POSAVE maxtime 0.1 - 100 mashorstd maxverstd 0.1 - 100 0.1 - 100 Description Command Maximum amount of time that positions are to be averaged (hours) Option: desired horizontal standard deviation (m) Option: desired vertical standard deviation (m) Example: posave 2,3,4 94 MiLLennium Command Descriptions Manual C Commands Summary RESET This command performs a hardware reset. Following a RESET command, the GPSCard will initiate a cold-start bootup. Therefore, the receiver configuration will revert to the factory default if no user configuration was saved or the last SAVECONFIG settings. Syntax: RESET See also the CRESET, where the differences between these three commands are explained, and FRESET commands. MiLLennium Command Descriptions Manual 95 C Commands Summary RESETHEALTH This command cancels the SETHEALTH command and restores the health of a satellite to the broadcast value contained in the almanac and ephemeris data. Syntax: RESETHEALTH Syntax prn Range Value RESETHEALTH prn 1 - 32 Description Command The PRN integer number of the satellite to be restored. Example: resethealth 4 RESETHEALTHALL This command resets the health of all satellites to the broadcast values contained in the almanac and ephemeris data. Syntax: RESETHEALTHALL 96 MiLLennium Command Descriptions Manual C RINEX Commands Summary Receiver-Independant Exchange Format The RINEX format is a broadly-accepted, receiver-independent format for storing GPS data. It features a nonproprietary ASCII file format that can be used to combine or process data generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990; subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types observation files, broadcast navigation message files and meteorological data files. Please see Chapter 7, Rinex Standard Commands and Logs for further details. MiLLennium Command Descriptions Manual 97 C Commands Summary RTCM16T This is a NovAtel command relating to the RTCM Standard ASCII message that can be sent out in RTCM Type 16 format. Once created, the RTCM16T message can be viewed in the RCCA command settings list. The text message can also be logged using the RTCM16 or RTCM16T log option. This command will limit the input message length to a maximum of 90 ASCII characters. See Chapter 6, Message Formats, RTCM Commands and Logs, for related topics. 98 MiLLennium Command Descriptions Manual C Commands Summary RTCMRULE This command allows the user flexibility in the usage of the RTCM Standard "bit rule". See Chapter 6, Message Formats, 6.2 RTCM - Format Messages, for further information. MiLLennium Command Descriptions Manual 99 C Commands Summary RTKMODE This command sets up the RTK (RT-2 or RT-20) mode. Invoking this command allows you to set different parameters and control the operation of the RTK system. The RTKMODE command is actually a family of commands; a description of the various arguments and options is as follows. Some arguments require data input, while others do not. Certain arguments can be used only at the reference station, and others only at the remote station. The structure of the syntax is shown below, followed by a detailed description of each argument. NOTE: While the arguments available for the remote station can be used in conjunction with either RTCA or RTCM-format messaging, the arguments available for the reference station can presently be used only in conjunction with RTCA-format messaging. Syntax - Reference Station (currently, for RTCA-format messaging only): RTKMODE sv_entries RTKMODE elev_mask Command 4to 20 0to 90 Argument Data Range Default RTKMODE sv_entries elev_mask 4 to 20 0 to 90 12 2 Syntax - Remote Station (for RTCA or RTCM-format messaging): RTKMODE default RTKMODE enable RTKMODE disable RTKMODE reset RTKMODE auto RTKMODE static RTKMODE kinematic RTKMODE fixed RTKMODE float RTKMODE unknown_baseline RTKMODE known_llh_position RTKMODE know_ecef_baseline 100 lat ∆x lon ∆y hgt ∆z [2σ] [m/e] [2σ] MiLLennium Command Descriptions Manual C Command Argument Commands Summary Default Argument Data Range RTKMODE default enable or disable reset auto, static or kinematic fixed or float unknown_baseline, default enable auto fixed unknown_baseline known_llh_position lat,lon,hgt,[2σ],[m/e] or lat: 0 to ± 90 lon: 0 to ± 360 hgt: -1000 to +20 000 000 2σ: 0 to 0.03 m/e: m or e (m = default) known_ecef_baseline ∆x, ∆y,∆z,[2σ] (∆x)2 + (∆y)2 +(∆z)2 ≤ (1 000 000)2 2σ: 0 to 0.03 Below is additional information for each argument: Station Reference Command rtkmode Argument elev_mask Data elevation (range 0 to 90, default = 2) RTKMODE ELEV_MASK ELEVATION causes transmission of observations for satellites above this elevation angle only. The elevation angle has units of degrees, and can be a decimal fraction value. At this time, this command affects RTCAOBS (RTCA Type 7) messages but not RTCM Type 59 messages; if RTCM-format messaging is being used, then observations for a certain satellite are transmitted as soon as it becomes visible. Example: rtkmode elev_mask 10.5 Station Command Argument Remote rtkmode default RTKMODE DEFAULT, when issued at the remote station, all RTK parameters are returned to their default values. Station Remote Command Argument rtkmode enable (default) disable RTKMODE ENABLE, when issued at the remote station, turns on its ability to receive and process RTCA or RTCM messages. RTKMODE DISABLE exits the RTK positioning mode. MiLLennium Command Descriptions Manual 101 C Commands Summary Station Remote Command rtkmode Argument Data unknown_baseline (default) known_llh_position lat,lon,height,[2σ],[m/e] known_ecef_baseline ∆x, ∆y, ∆z,[2σ] RTKMODE UNKNOWN_BASELINE prevents the RTK system from using any baseline information in the initial calculation of ambiguities. It cancels the effect of the RTKMODE KNOWN_LLH_POSITION or RTKMODE KNOWN_ECEF_BASELINE command. It indicates to the RT-2 software that the previously entered baseline can no longer be considered valid, usually because the antenna is starting to move. RTKMODE KNOWN_LLH_POSITION LAT,LON,HEIGHT,[2σ],[M/E] requires the latitude, longitude and height of the initial remote station antenna location. It can be used to initialize the RT–2 algorithms from a known antenna position. It speeds up ambiguity resolution by indicating to the RT-2 software the exact length of the vector between the remote and reference station antennas. It only affects the operation of an RT-2 system on baselines not exceeding 30 km. LAT requires a decimal fraction format; a negative sign implies South latitude. LON requires a decimal fraction format; a negative sign implies West longitude. HEIGHT (in meters) can refer either to mean sea level (default) or to an ellipsoid. The optional 2σ defines the accuracy (2 sigma, 3 dimensional) of the input position, in metres; it must be 0.03 m or less to cause the RT-2 algorithms to undergo a forced initialization to fixed integer ambiguities. If no value is entered, a default value of 0.30 m is assumed; this will not cause an initialization to occur. The optional M or E refers to the height: if “M” is entered, the height will be assumed to be above mean sea level (MSL). Note that when an MSL height is entered, it will be converted to ellipsoidal height using the NovAtel internal undulation table or the last value entered with the “UNDULATION” command. You may directly indicate an ellipsoidal height by using the optional “E” flag. Example: rtkmode known_llh_position 51.113618,-114.04358,1059.15,0.01,e RTKMODE KNOWN_ECEF_BASELINE ∆X,∆Y,∆Z,[2σ] can be used to initialize the RT–2 algorithms from a known ECEF baseline. The RT-2 system uses this to initialize its ambiguities. It only affects the operation of an RT2 system on baselines not exceeding 30 km. The ∆X,∆Y,∆Z values represent the remote station’s position minus the reference position, along each axis, in metres. The optional 2σ defines the accuracy (2 sigma, 3 dimensional) of the input baseline, in metres; it must be 0.03 m or less to cause the RT-2 algorithms to do a forced initialization to fixed integer ambiguities. If no value is entered, a default value of 0.30 m is assumed; this will not cause an initialization to occur. Example: rtkmode known_ecef_baseline 3583,2165,567,0.02 NOTE: You must be very careful when using these last two commands; erroneous input will cause poor performance and/or erroneous output. It is also very important to follow these command with an RTKMODE UNKNOWN_BASELINE command before any motion begins. 102 MiLLennium Command Descriptions Manual C Station Remote Command rtkmode Commands Summary Argument auto (default) static kinematic RTKMODE AUTO configures the RTK system to automatically detect motion. It is the default mode. It will reliably detect motion of 2.5 cm/sec or greater. If you are undergoing motion slower than this which covers more than 2 cm, you should use the manual mode selection commands (static and kinematic). RTKMODE STATIC forces the RTK software to treat the remote station as though it were stationary, regardless of the output of the motion detector. Note: If the remote station is undergoing > 2.5 cm peak-to-peak oscillations (e.g. due to wind or vibration), the performance can be increased by declaring STATIC mode when the remote station is not undergoing any motion other than the vibration. If the remote station starts to move while STATIC mode is declared, repeated resets and unpredictable performance will result. For reliable performance the antenna should not move more than 1-2 cm when in static mode. RTKMODE KINEMATIC forces the RTK software to treat the remote station as though it were in motion, regardless of the output of the motion detector. If the remote station is undergoing very slow steady motion (< 2.5 cm/sec for more than 5 seconds), you should declare KINEMATIC mode to prevent inaccurate results and possible resets. Station Remote Command rtkmode Argument fixed (default) float RTKMODE FIXED tells the RTK system to use fixed discrete ambiguities whenever the system is capable and can do so reliably; it may never do so for long baselines or poor geometries. Only RT-2 systems are capable of fixing ambiguities, so issuing this command on an RT-20 system will have no effect. RTKMODE FLOAT causes the system to compute only a floating ambiguity solution. L2 data will be used along with L1 data if the system is capable of generating L2 data. You can force the RT-2 software to not fix ambiguities when it normally would, but you cannot force it to fix ambiguities when it normally wouldn’t. Station Command Argument Remote rtkmode reset RTKMODE RESET causes the RTK algorithm (RT-20 or RT-2, whichever is active) to undergo a complete reset, forcing the system to restart the ambiguity resolution calculations. Station Reference Command rtkmode Argument sv_entries Data number (range 4 to 20, default = 12) RTKMODE SV_ENTRIES NUMBER causes the number of satellite measurements to be limited to the number indicated. NUMBER refers to the number of PRNs transmitted by the reference station; each PRN can have either an L1-only measurement or an L1/L2 pair of measurements. At this time, this command affects RTCAOBS (RTCA Type 7) messages but not RTCM Type 59 messages; if RTCM-format messaging is being used, then observations for all visible satellites are transmitted. Example: rtkmode sv_entries 8 MiLLennium Command Descriptions Manual 103 C Commands Summary SAVEALMA This command saves the latest almanac in non-volatile memory. The option ONNEW is the default; if a different setting is used, a ONNEW will resume after a reset. SAVECONFIG command must be issued or else Bit 21 in the receiver self-test status word (see Table D-5, Appendix D) indicates whether the latest almanac received by the GPS receiver is newer than the almanac saved in non-volatile memory (NVM). Syntax: SAVEALMA Command SAVEALMA option option Range Values (none) onnew onnext stop disable ➀ Description Command The latest received almanac is saved in NVM. Each almanac is saved in NVM upon reception unless if it is newer than the one already stored. This will occur continuously. The next received almanac will be saved in NVM unless it is identical to the one already stored. This only occurs once. Stops auto saving. Stops auto saving and prevents the use of the almanac, saved in NVM, on startup. Default onnew ➀The disable option must be followed by the SAVECONFIG command to have an effect. 104 MiLLennium Command Descriptions Manual C Commands Summary SAVECONFIG This command saves the user’s present configuration in non-volatile memory. Syntax: SAVECONFIG MiLLennium Command Descriptions Manual 105 C Commands Summary SEND This command is used to send ASCII printable data from the COM1 or COM2 or disk file to a specified communications port. This is a one-time command, therefore the data message must be preceded by the SEND command followed by the key ( ) each time you wish to send data. (Remember to use the MESSAGES command to disable error reporting whenever two GPSCards are connected together via the COM ports.) Syntax: SEND to-port Syntax SEND to-port data data Range Value Description Command Port option ASCII data COM1, COM2 up to 100 characters Scenario: Assume that you are operating GPSCards as reference and remote stations. It could also be assumed that the reference station is unattended but operational and you wish to control it from the remote station. From the remote station, you could establish the data link and command the reference station GPSCard to send differential corrections. Figure C-4 Using SEND Command $PVAA data log... COM1 send com1 log com 1 pvaa ontim COM 2 e5 COM 1 COM 2 messages com1 off send com1 log com1 pvaa ontime 5 Serial Cables Host PC - Reference (Operational with position fixed) 106 Host PC - Rover Rover station is commanding Reference to send PVAA differential logs MiLLennium Command Descriptions Manual C Commands Summary SENDHEX This command is like the SEND command but is used to send non-printable characters expressed as hexadecimal pairs. Syntax: SENDHEX to-port data Syntax SENDHEX to-port data Range Value COM1, COM2 • • • • even number of ASCII characters from set of 0-9, A-F spaces allowed between pairs of characters carriage return & line feed provided by entering ODOA at end of string maximum number of characters limited to about 1400 characters by command interpreter buffer (2800 ASCII characters pairs) MiLLennium Command Descriptions Manual Description Command Port option ASCII data 107 C Commands Summary SETDGPSID This command is used to enter a station ID. Once set, the receiver will only accept differential corrections from a station whose ID matches the set station ID. It is typically used when a station has data links containing RTCM or RTCA messages from several stations. By entering a specific station ID, the operator can select which station to listen to. Having set a station ID, incoming, RTCM, RTCMA, RTCA, RTCAA, and RTCAB messages will be received from only that station. When a valid station ID is entered, an improved data synchronization algorithm will be used. It is recommended to always set the station ID. This command can also be used to set the station ID for a GPSCard reference station. See FIX POSITION 4th parameter (station ID). Note: The SETDGPSID command does not affect RT2 or RT20 when using any of the possible messages RTCM59, and RTCAREF. RTCAOBS Syntax: SETDGPSID station ID # SETDGPSID all Syntax SETDGPSID station ID # Range Value 0 - 1023 or “xxxx” or all Example 1: SETDGPSID 1023 Example 2: SETDGPSID “abcd” 108 Description Command Reference station ID number for RTCM Default all Reference station name for RTCA where ”xxxx” are four alphanumeric characters, entered between double quotes Accepts differential corrections from any station MiLLennium Command Descriptions Manual C Commands Summary SETHEALTH This command permits you the flexibility to override the broadcast health of a satellite. Under certain conditions and applications, it may be desirable to track and use information from a GPS satellite even though its health has been set bad by the GPS control segment. To SETHEALTH for more than one satellite, the command must be reissued for each satellite. IMPORTANT: There is usually a reason when the GPS Control Segment sets a satellite to bad health condition. If you decide to ignore the health warnings and use the satellite information, UNPREDICTABLE ERRORS MAY OCCUR. Syntax: SETHEALTH prn Syntax SETHEALTH prn health health Range Value 1 - 32 good or bad Description Default Command A satellite PRN integer number Desired health; resethealthall Example: sethealth 4,good MiLLennium Command Descriptions Manual 109 C Commands Summary SETL1OFFSET The characteristic signal delays introduced by the antenna, coaxial cable and GPSCard RF section will vary from one system configuration to another. These delays are measurable using external test equipment. For applications which involve very precise time transfer, or where ranges are used from multiple receivers, it may be necessary to add an offset to the L1 pseudorange to compensate for these delays. This is equivalent to a system calibration in that it corrects for inter-receiver range bias It does not affect the output position, and it is unrelated to data latencies. NOTE: This feature is to be used by advanced users only. Its intended application is for use in multi-card systems, in which case the clocks on the different GPSCards must be synchronized. The command is not necessary for most applications. Syntax: SETL1OFFSET distance Command Range Values SETL1OFFSET distance -10 to +10 Description Pseudorange offset (m) Example: setl1offset 1.348693 110 MiLLennium Command Descriptions Manual C Commands Summary SETNAV This command permits entry of one set of navigation waypoints (see Figure C-5). The origin (FROM) and destination (TO) waypoint coordinates entered are considered on the ellipsoidal surface of the current datum (default WGS84). Once SETNAV has been set, you can monitor the navigation calculations and progress by observing the NAVA/B, GPRMB, and GPZTG log messages. Track offset is the perpendicular distance from the great circle line drawn between the FROM lat-lon and TO lat-lon waypoints. It establishes the desired navigation path, or track, that runs parallel to the great circle line, which now becomes the offset track, and is set by entering the track offset value in metres. A negative track offset value indicates that the offset track is to the left of the great circle line track. A positive track offset value (no sign required) indicates the offset track is to the right of the great circle line track (looking from origin to destination). See Figure C-5 for clarification. Syntax: SETNAV from-lat track offset from-lon to-lat from-port to-port to-lon SETNAV disable Syntax Range Value SETNAV from-lat 0± 90 from-lon 0± 360 to-lat to-lon track offset 0± 90 0± 360 0± 1000 from-port to-port 1 to 5 characters 1 to 5 characters Description Command Origin latitude in units of degrees/decimal degrees. A negative sign implies South latitude. No sign implies North latitude. Origin longitude in units of degrees/decimal degrees. A negative sign implies West longitude. No sign implies East longitude. Destination latitude in units of degrees/decimal degrees Destination longitude in units of degrees/decimal degrees Waypoint great circle line offset (in kilometres); establishes offset track; positive indicates right of great circle line; negative indicates left of great circle line Optional ASCII station name Optional ASCII station name Default disable Example setnav 51.1516 -114.16263 51.16263 -114.1516 -125.23 from to Example: setnav 51.1516,-114.16263,51.16263,-114.1516,-125.23,from,to MiLLennium Command Descriptions Manual 111 C Commands Summary Figure C-5 Illustration of SETNAV Parameters Reference Description 1 2 3 4 5 6 7 TO, lat-lon X-Track perpendicular reference point Current GPS position A-Track perpendicular reference point X-Track (cross-track) A-Track (along track) Distance and bearing from 3 to 1 112 MiLLennium Command Descriptions Manual C Commands Summary SETTIMESYNC This command enables or disables time synchronization, which permits two GPSCards in a master/slave relationship to be synchronized to a common external clock for range comparisons. By default, this function is disabled. With SETTIMESYNC enabled, a slave unit is able to interpret injected ($)TM1A/B data messages; for more information, please refer to the comments relating to the ($)TM1A/B special data messages, and the 1PPS signal. Syntax: SETTIMESYNC Command SETTIMESYNC flag flag Range of Values enable or disable Description Enable or disable time synchronization Default disable Example: settimesync enable Note: This command is intended for advanced users of GPS only. MiLLennium Command Descriptions Manual 113 C Commands Summary UNASSIGN This command cancels a previously issued ASSIGN command and the channel reverts to automatic control. If a channel has reached state 4 (PLL), the satellite being tracked will not be dropped when the UNASSIGN command is issued, unless it is below the elevation cutoff angle, and there are healthy satellites above the ecutoff that are not already assigned to other channels. Syntax: UNASSIGN Syntax UNASSIGN channel Example: channel Range Value 0 - 11 Description Command Reset channel to automatic search and acquisition mode Default unassignall unassign 11 UNASSIGNALL This command cancels all previously issued ASSIGN commands for all channels. Tracking and control for each channel reverts to automatic mode. If any of the channels have reached state 4 (PLL), the satellites being tracked will not be dropped when the UNASSIGNALL command is issued, unless they are below the elevation cutoff angle, and there are healthy satellites above the ecutoff that are not already assigned to other channels. Syntax: 114 UNASSIGNALL MiLLennium Command Descriptions Manual C Commands Summary UNDULATION This command permits you to either enter a specific geoidal undulation value or use the internal table of geoidal undulations. The separation values only refer to the separation between the WGS84 ellipsoid and the geoid, regardless of the datum chosen, see the PRTKA/B log in Chapter 4 and Appendix D. Syntax: UNDULATION Syntax UNDULATION separation separation Range Value Description table Command Selects the internal table of undulations and ignores any previously entered value. The internal table utilizes OSU - 89B 1.5º x ~1.5º. or enter a value Default table A numeric entry that overrides the internal table with a value in metres. Example 1: undulation table Example 2: undulation -5.6 Please see Appendix A, A.2 Height Relationships for a description of the relationships in Figure C-6. Figure C-6 MiLLennium Command Descriptions Manual Illustration of Undulation 115 C Commands Summary UNFIX This command removes all position constraints invoked with any of the FIX commands (FIX POSITION, FIX HEIGHT, or FIX VELOCITY). Syntax: UNFIX UNLOCKOUT This command allows a satellite which has been previously locked out (LOCKOUT command) to be reinstated in the solution computation. If more than one satellite is to be reinstated, this command must be reissued for each satellite reinstatement. Syntax: UNLOCKOUT prn Syntax UNLOCKOUT prn Range Value 1 - 32 Description Default Command A single satellite PRN to be reinstated unlockoutall Example: unlockout 8 UNLOCKOUTALL This command allows all satellites which have been previously locked out (LOCKOUT command) to be reinstated in the solution computation. Syntax: UNLOCKOUTALL 116 MiLLennium Command Descriptions Manual C Commands Summary UNLOG This command permits you to remove a specific log request from the system. The [port] parameter is optional. If [port] is not specified, it is defaulted to the port that the command was received on. This feature eliminates the need for you to know which port you are communicating on if you want logs to come back on the same port you are sending commands on. Syntax: UNLOG Syntax UNLOG [port] datatype [port] datatype Range Value COM1, COM2 any valid log Description Default Command COMn port from which log originated The name of the log to be disabled unlogall Example: unlog com1,posa unlog posa UNLOGALL If [port] is specified (COM1 or COM2) this command disables all logs on the specified port only. All other ports are unaffected. If [port] is not specified this command disables all logs on all ports. Syntax: UNLOGALL [port] Note: This command does not disable logs that have the HOLD attribute (see description for LOG command). To disable logs with the HOLD attribute, use the UNLOG command. MiLLennium Command Descriptions Manual 117 C Commands Summary USERDATUM This command permits entry of customized ellipsoidal datum parameters. Use this command in conjunction with the DATUM command. The default setting is WGS84. Syntax: USERDATUM semi-major Syntax Range Value USERDATUM semi-major min. 6300000.0 max. 6400000.0 min. 290.0 max. 305.0 min. - 2000.0 max. 2000.0 flattening dx,dy,dz rx,ry,rz min. max. -10 10 scale min. max. -10 10 flattening dx dy Description dz rx ry rz scale Default Example Command Datum Semi-major Axis (a) in metres 6378137.000 userdatum 6378206.4 Reciprocal Flattening, 1/f = a/(a-b) 298.257223563 294.9786982 Datum offsets from WGS84 in metres: 0.000,0.000,0.000 These will be the translation values between your datum and WGS84 (internal reference) Datum Rotation Angle about X, Y and Z axis (sec of arc): 0.000,0.000,0.000 These values will be the rotation between your datum and WGS84 Scale value is the difference in ppm between your datum 0.000 and WGS84 -12,147,192 0,0,0 0 Example: userdatum 6378206.4,294.9786982,-12,147,192,0,0,0,0 118 MiLLennium Command Descriptions Manual C Commands Summary VERSION Use this command to determine the current software version of the GPSCard. The response to the command is logged to the port from which the command originated. VERSION Syntax: VERSION Command VERSION Response Syntax Card type Model # S/N HW Rev SW Rev Date Example: version OEM-3 MILLENRT2 ESN251448497 HW 3-1 SW 4.433/2.03 Feb 18/97 com1> MiLLennium Command Descriptions Manual 119 D Logs summary D D LOGS SUMMARY LOGS SUMMARY LOG DESCRIPTIONS ALMA/B Decoded Almanac This log contains the decoded almanac parameters from subframes four and five as received from the satellite with the parity information removed and appropriate scaling applied. Multiple messages are transmitted, one for each SV almanac collected. The Ionospheric Model parameters (IONA) and the UTC Time parameters (UTCA) are also provided, following the last almanac records. For more information on Almanac data, refer to the GPS SPS Signal Specification. (See Appendix F of this manual for References.) MiLLennium cards will automatically save almanacs in their non-voatile memory (NVM), therefore creating an almanac boot file would not be necessary. 120 MiLLennium Command Descriptions Manual D Logs summary ALMA Structure: $ALMA prn ecc Mo af0 ra w A incl-angle seconds week rate-ra cor-mean-motion af1 health-4 health-5 health-alm *xx [CR][LF] ALMA FORMAT Field # Field type Data Description Example 1 2 3 4 5 6 7 8 9 $ALMA prn ecc seconds week rate-ra ra w Mo Log header Satellite PRN number for current message, dimensionless Eccentricity, dimensionless Almanac reference time, seconds into the week Almanac reference week (GPS week number) Rate of right ascension, radians Right ascension, radians Argument of perigee, radians Mean anomaly, radians $ALMA 1 3.55577E-003 32768 745 -7.8860E-009 -6.0052951E-002 -1.1824254E+000 1.67892137E+000 10 Clock aging parameter, seconds -1.8119E-005 11 af0 af1 Clock aging parameter, seconds/second -3.6379E-012 12 13 14 15 16 17 18 19 cor-mean-motion A incl-angle health-4 health-5 health-alm *xx [CR][LF] Corrected mean motion, radians/second Semi-major axis, metres Angle of inclination, radians Anti-spoofing and SV config from subframe 4, page 25 SV health, 6 bits/SV (subframe 4 or 5, page 25) SV health, 8 bits (almanac) Checksum Sentence terminator 1.45854965E-004 2.65602281E+007 9.55576E-001 1 0 0 *20 [CR][LF] 1 - 19 $ALMA Next satellite PRN almanac message 1 - 19 $ALMA Last satellite PRN almanac message 1 - 11 $IONA Ionospheric Model Parameters 1 - 11 $UTCA UTC Time Parameters Example: $ALMA,1,3.55577E-003,32768,745,-7.8860E-009,-6.0052951E-002,-1.1824254E+000, 1.67892137E+000,-1.8119E-005,-3.6379E-012,1.45854965E-004,2.65602281E+007, 9.55576E-001,1,0,0*20[CR][LF] ... $ALMA,31,4.90665E-003,32768,745,-8.0460E-009,3.05762855E+000,6.14527459E-001, 1.69958217E+000,6.67572E-006,3.63797E-012,1.45861888E-004,2.65593876E+007, 9.61664E-001,1,0,0*13[CR][LF] MiLLennium Command Descriptions Manual 121 D Logs summary IONA FORMAT Structure: $IONA act a1ot a2ot a3ot bct b1ot b2ot b3ot *xx Field # Field type [CR][LF] Data Description Example 1 2 3 4 $IONA act a1ot a2ot Log header Alpha constant term, seconds Alpha 1st order term, sec/semicircle Alpha 2nd order term, sec/(semic.)2 $IONA 1.0244548320770265E-008 1.4901161193847656E-008 -5.960464477539061E-008 5 a3ot -1.192092895507812E-007 6 7 8 bct b1ot b2ot Alpha 3rd order term, sec/(semic.)3 Beta constant term, seconds Beta 1st order term, sec/semicircle Beta 2nd order term, sec/(semic.)2 9 b3ot -1.966080000000001E+005 10 11 *xx [CR][LF] Beta 3rd order term, sec/(semic.)3 Checksum Sentence terminator 8.8064000000000017E+004 3.2768000000000010E+004 -1.966080000000001E+005 *02 [CR][LF] Example: $IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008, -1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004, -1.966080000000001E+005,-1.966080000000001E+005*02[CR][LF] UTCA FORMAT Structure: $UTCA delta-time Field # 1 2 3 4 5 6 7 8 9 10 11 pct lsop Field type $UTCA pct p1ot data-ref wk #-utc wk #-lset delta-time lsop day #-lset *xx [CR][LF] p1ot data-ref day #-lset *xx wk#-utc wk#-lset [CR][LF] Data Description Example Log header Polynomial constant term, seconds Polynomial 1st order term, seconds/second UTC data reference time, seconds Week number of UTC reference, weeks Week number for leap sec effect time, weeks Delta time due to leap sec, seconds For use when leap sec on past, seconds Day number for leap sec effect time, days Checksum Sentence terminator $UTCA -2.235174179077148E-008 -1.243449787580175E-014 32768 745 755 9 10 5 *37 [CR][LF] Example: $UTCA,-2.235174179077148E-008,-1.243449787580175E-014,32768,745,755,9,10,5*37 [CR][LF] 122 MiLLennium Command Descriptions Manual D Logs summary ALMB ALMB FORMAT: Message ID = 18 Field # 1 (header) Field Type 2 3 4 5 6 7 8 9 10 Sync Checksum Message ID Message byte count Satellite PRN number Eccentricity Almanac ref. time Almanac ref. week Omegadot - rate of right ascension Right ascension Argument of perigee Mean anomaly Clock aging parameter 11 Clock aging parameter 12 13 14 15 16 17 Corrected mean motion Semi-major axis Angle of inclination Sv health from subframe 4, discrete Sv health from subframe 5, discrete Sv health from almanac, discrete IONB FORMAT: Field # 1 (header) Message byte count = 120 Message ID = 16 Bytes Format Units Offset w Mo af0 3 1 4 4 4 8 8 4 8 8 8 8 8 integer double double integer double double double double double seconds weeks radians/second radians radians radians seconds 0 3 4 8 12 16 24 32 36 44 52 60 68 af1 8 double seconds/second 76 8 8 8 4 4 4 double double double integer integer integer radians/second metres radians 84 92 100 108 112 116 A Message byte count = 76 Field Type Bytes Format 2 3 4 Sync Checksum Message ID Message byte count Alpha constant term Alpha 1st order term Alpha 2nd order term 3 1 4 4 8 8 8 char char integer integer double double double 5 Alpha 3rd order term 8 double 6 7 8 Beta constant term Beta 1st order term Beta 2nd order term 8 8 8 9 Beta 3rd order term 8 MiLLennium Command Descriptions Manual Units seconds sec/semicircle sec/(semic.)2 Offset 0 3 4 8 12 20 28 36 double double double sec/(semic.)3 seconds sec/semic sec/(semic.)2 double sec/(semic.)3 68 44 52 60 123 D Logs summary UTCB FORMAT: Field # 1 (header) 2 3 4 5 6 7 8 9 124 Message ID = 17 Field Type Sync Checksum Message ID Message byte count Polynomial constant term Polynomial 1st order term UTC data reference time Week number UTC reference Week number for leap sec effect time Delta time due to leap sec For use when leap sec on past Day number for leap sec effect time Message Byte Count = 52 Bytes 3 1 4 4 8 8 4 4 4 4 4 4 Format char char integer integer double double integer integer integer integer integer integer Units seconds seconds/second seconds weeks weeks seconds seconds days Offset 0 3 4 8 12 20 28 32 36 40 44 48 MiLLennium Command Descriptions Manual D Logs summary BSLA/B Baseline Measurement RTK This log contains the most recent matched baseline representing the vector from the reference station receiver to the remote station receiver. It is expressed in ECEF coordinates with corresponding uncertainties along each axis, and a time tag. The estimated variance of the baseline in ECEF XYZ coordinates is the same as the XYZ position variance. It is recommended that you use the trigger ‘on changed’ which will log the selected data only when the data has changed. BSLA Structure: $BSLA ∆x week ∆y seconds ∆z rtk status Field # ∆x σ posn type #sv $BSLA week seconds #sv #high 6 7 8 9 10 11 12 13 14 15 16 17 18 L1L2 # high ∆x ∆y ∆z ∆x σ ∆y σ ∆z σ soln status rtk status posn type stn ID *xx [CR][LF] L1L2 #high ∆y σ ∆z σ soln status stn ID *xx [CR][LF] Field type 1 2 3 4 5 #high Data Description Log header GPS week number GPS time into the week (in seconds) Number of matched satellites; may differ from the number in view. Number of matched satellites above RTK mask angle; observations from satellites below mask are heavily de-weighted. Number of matched satellites above RTK mask angle with both L1 and L2 available ECEF X baseline component (remote stn. - reference stn.); in metres ECEF Y baseline component (remote stn. - reference stn.); in metres ECEF Z baseline component (remote stn. - reference stn.); in metres Standard deviation of ∆x solution element; in metres Standard deviation of ∆y solution element; in metres Standard deviation of ∆z solution element; in metres Solution status (see Table D-1) RTK status (see Tables D-3, D-4 ) Position type (see Table D-2) Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Checksum Sentence terminator Example $BSLA 872 174962.00 8 7 7 -1.346 -3.114 -2.517 0.005 0.004 0.005 0 0 4 119 *36 [CR][LF] Example: $BSLA,872,174962.00,8,7,7,-1.346,-3.114, -2.517,0.005,0.004,0.005,0,0,4,119*36[CR][LF] MiLLennium Command Descriptions Manual 125 D Logs summary BSLB Format: Message ID = 59 Message byte count = 100 Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 126 Data Sync Checksum Message ID Message byte count Week number GPS time into the week Number of matched satellites (00-12) Number of matched satellites above RTK mask angle Number of matched satellites above RTK mask angle with both L1 and L2 available ECEF X baseline ECEF Y baseline ECEF Z baseline Standard deviation of X baseline Standard deviation of Y baseline Standard deviation of Z baseline Solution status (see Table D-1) RTK status (see Tables D-3, D-4 ) Position type (see Table D-2) Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Bytes Format 3 1 4 4 4 8 4 4 char char integer integer integer double integer integer 4 integer 8 8 8 8 8 8 4 4 4 4 double double double double double double integer integer integer integer Units weeks seconds Offset 0 3 4 8 12 16 24 28 32 metres metres metres metres metres metres 36 44 52 60 68 76 84 88 92 96 MiLLennium Command Descriptions Manual D Logs summary Table D-1 GPSCard Solution Status Value 0 1 2 3 Description Solution computed Insufficient observations No convergence Singular ATPA Matrix Covariance trace exceeds maximum (trace > 1000 m) Test distance exceeded (maximum of 3 rejections if distance > 10 km) Not yet converged from cold start Height or velocity limit exceeded. (In accordance with COCOM export licencing restrictrictions) 4 5 6 7 Higher numbers are reserved for future use Table D-2 Position Type Type 0 1 2 3 4 Definition No position Single point position Differential pseudorange position RT-20 position RT-2 position Higher numbers are reserved for future use Table D-3 RTK Status for Position Type 3 (RT-20) Status 0 1 2 3 4 5 6 7 8 Definition Floating ambiguity solution (converged) Floating ambiguity solution (not yet converged) Modelling reference phase Insufficient observations Variance exceeds limit Residuals too big Delta position too big Negative variance RTK position not computed Higher numbers are reserved for future use Table D-4 RTK Status for Position Type 4 (RT-2) Status 0 1 2 3 4 5 6 7 8 9 10 Definition Narrow lane solution Wide lane derived solution Floating ambiguity solution (converged) Floating ambiguity solution (not yet converged) Modelling reference phase Insufficient observations Variance exceeds limit Residuals too big Delta position too big Negative variance RTK position not computed Higher numbers are reserved for future use MiLLennium Command Descriptions Manual 127 D Logs summary CDSA/B Communication and Differential Decode Status The GPSCard maintains a running count of a variety of status indicators of the data link. This log outputs a report of those indicators. Parity and framing errors will occur if poor transmission lines are encountered or if there is an incompatibility in the data protocol. If errors occur, you may need to confirm the bit rate, number of data bits, number of stop bits and parity of both the transmit and receiving ends. Overrun errors will occur if more characters are sent to the UART than can be removed by the on-board microprocessor. CDSA Structure $cdsa week seconds xon1 csts1 parity1 overrun1 framing1 rx1 tx1 xon2 cts2 parity2 overrun2 framing2 rx2 rtca crc rtcaa chk rtca good rtcm par rtcma chk rtcm good dcsb chk dcsb good res’d res’d res’d *xx Field # Field type 1 $CDSA Log header $CDSA 2 week GPS week number 787 3 seconds GPS seconds into the week 500227 4 xon1 Flag to indicate that the com1 is using XON/XOFF handshaking protocol and port has received an xoff and will wait for an xon before sending any more data. 0 5 cts1 Flag to indicate that com1 is using CTS/RTS handshake protocol and cts line port has been asserted. The port will wait for the line to de-assert before sending any more data. 0 6 parity1 A running count of character parity errors from the UART of COM1 0 7 overrun1 A running count of UART buffer overrun errors of COM1 0 8 framing1 A running count of character framing error from the UART of COM1 0 9 rx1 A running count of the characters rececived from COM1 0 10 tx1 A running count of the characters sent out to COM1 0 11 xon2 Flag to indicate that COM2 is using XON/XOFF handshaking protocol and port has received an xoff and will wait for an xon before sending any more data. 0 12 cts2 Flag to indicate that COM2 is using CTS/RTS handshake protocol and cts line port has been asserted. The Port will wait for the line to de-assert before sending any more data. 0 13 parity2 A running count of character parity errors from the UART of COM2 0 14 overrun2 A running count of UART buffer ourerrun errors of COM2 0 15 framing2 A running count of character framing error from the UART of COM2 0 16 rx2 A running count of the characters received from COM2 0 17 tx2 A running count of characters sent out to COM2 9 18 rtcacrc A running count of RTCA CRC failures 0 19 rtcaachk A running count of invalid ASCII $RTCA,....,*xx records indicating that the ASCII checksum “xx” failed. 0 20 rtcagood A running count of RTCA records tht pass error checking 0 21 rtcmpar A running count of 30 bit RTCM parity failures 0 22 rtcmachk A running count of invalid ASCII $RTCM,....,*xx records indicating that the ASCII checksum “xx” failed. 0 23 rtcmgood A running count of RTCM records that pass error checking 0 24 dcsachk A running count of invalid ASCII $DCSA,...., *xx records 0 128 dcsa chk tx2 dsca good [CR][LF] Data Description Example MiLLennium Command Descriptions Manual D Logs summary Field # Field type 25 dcsagood Data Description Example A running count of DCSA records that pass error checking 0 A running count of invalid binary DCSB records 0 A running count of DCSB records that pass error checking 0 28 Reserved for future use 0 29 Reserved for future use 0 26 7dcsbchk 27 dcsbgood 30 Reserved for future use 0 31 *xx Checksum *33 32 [CR][LF] Sentence terminator [CR][LF] Example: $CDSA,787,500227,0,0,0,0,0,0,9,0,0,0,0,0,0,9,0,0,0,0,0,0,0,0,0,0,0,0,0 *33[CR][LF] MiLLennium Command Descriptions Manual 129 D Logs summary CDSB Format: Message ID = 39 Field # Message byte count = 128 Data Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer 4 Message byte count 4 integer 8 2 Week number 4 integer weeks 12 3 Time of week 4 integer seconds 16 4 Xon COM1 4 integer 20 5 CTS COM1 4 integer 24 6 Parity errors COM1 4 integer 28 7 Overrun errors COM1 4 integer 32 8 Framing error COM1 4 integer 36 9 Bytes received in COM1 4 integer 40 10 Bytes sent out COM1 4 integer 44 11 Xon COM2 4 integer 48 12 CTS COM2 4 integer 52 13 Parity errors COM2 4 integer 56 14 Overrun errors COM2 4 integer 60 15 Framing error COM2 4 integer 64 16 Bytes received in COM2 4 integer 68 17 Bytes sent out COM2 4 integer 72 18 RTCA CRC fails 4 integer 76 19 RTCAA checksum fails 4 integer 80 20 RTCA records passed 4 integer 84 21 RTCM parity fails 4 integer 88 22 RTCMA checksum fails 4 integer 92 23 RTCM records passed 4 integer 96 24 DCSA checksum 4 integer 100 25 DCSA records passed 4 integer 104 26 DCSB checksum fails 4 integer 108 27 DCSB records passed 4 integer 112 28 Reserved 4 integer 116 29 Reserved 4 integer 120 30 Reserved 4 integer 124 130 MiLLennium Command Descriptions Manual D Logs summary CLKA/B Receiver Clock Offset Data This record is used to monitor the state of the receiver time. Its value will depend on the CLOCKADJUST command. If CLOCKADJUST is enabled, then the offset and drift times will approach zero. If not enabled, then the offset will grow at the oscillator drift rate. Disabling CLOCKADJUST and monitoring the CLKA/B log will allow you to determine the error in your GPSCard receiver reference oscillator as compared to the GPS satellite reference. All logs report GPS time not corrected for local receiver clock error. To derive the closest subtract the clock offset shown in the CLKA log (field 4) from GPS time reported. GPS time one must The internal units of the new clock model’s three states (offset, drift and GM state) are meters, meters per second, and meters. When scaled to time units for the output log, these become seconds, seconds per second, and seconds, respectively. Note that the old units of the third clock state (drift rate) are seconds per second per second. CLKA Structure: $CLKA week drift std Field # seconds cm status offset *xx Field type 1 2 3 4 $CLKA week seconds offset 5 drift 6 SA G-M state 7 8 9 offset std drift std cm status 10 11 *xx [CR][LF] drift SA G-M state offset std [CR][LF] Data Description Log header GPS week number GPS seconds into the week Receiver clock offset, in seconds. A positive offset implies that the receiver clock is ahead of GPS Time. To derive GPS time, use the following formula: GPS time = receiver time - (offset) Receiver clock drift, in seconds per second. A positive drift implies that the receiver clock is running faster than GPS Time. This field contains the output value of the Gauss-Markov Selective Availability clock dither estimator, in units of seconds. The value reflects both the collective SA-induced short-term drift of the satellite clocks as well as any range bias discontinuities that would normally affect the clock model’s offset and drift states. Standard deviation of receiver clock offset, in seconds Standard deviation of receiver drift, in seconds per second Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that the model is in the process of stabilization Checksum Sentence terminator Example $CLKA 637 511323.00 -4.628358547E-003 -2.239751396E-007 2.061788299E-006 5.369997167E-008 4.449097711E-009 0 *7F [CR][LF] Example $CLKA,841,499296.00,9.521895494E-008,-2.69065747E-008,2.061788299E-006, 9.642598169E-008,8.685638908E-010,0*4F MiLLennium Command Descriptions Manual 131 D Logs summary CLKB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 132 Message ID = 02 Message byte count = 68 Field Type Bytes Sync Checksum Message ID Message byte count Week number Seconds of week Clock offset Clock drift SA Gauss-Markov state StdDev clock offset StdDev clock drift Clock model status 3 1 4 4 4 8 8 8 8 8 8 4 Format char char integer integer integer double double double double double double integer Units weeks seconds seconds seconds per second seconds seconds seconds per second Offset 0 3 4 8 12 16 24 32 40 48 56 64 MiLLennium Command Descriptions Manual D Logs summary CLMA/B Receiver Clock Model The CLMA and CLMB logs contain the current clock-model matrices of the GPSCard. These logs can be both generated and received by a GPSCard. NOTE: Only advanced users should seek to alter the clock model parameters of a GPSCard. Throughout the following, these symbols are used: B= range bias (m) BR = range bias rate (m/s) SAB = Gauss-Markov process representing range bias error due to SA clock dither (m) For further information, please refer to the documentation given for the clka/b log. The standard clock model now used is as follows: clock parameters array = [ B BR SAB] covariance matrix = σB σB σBR σB σSAB σBR σB σ σBR σSAB 2 2 BR σSAB σB σSAB σBR σSAB 2 CLMA Structure: $CLMA status parameters Field # covariance Field type 1 2 $CLMA status 3 reject 4 noise time 5 update 6-8 parameters 9 - 17 covariance 18 19 *xx [CR][LF] reject noise time *xx update [CR][LF] Data Description Log header Status of clock model (0 = good; -1 to -20 = bad) Number of rejected range bias measurements (max. = 5) GPS time of last estimate (seconds) - since Jan. 3, 1980 GPS time of last update (seconds) - since Jan. 3, 1980 Parameters array (1 x 3 = 3 elements) Covariance matrix (3x3 = 9 elements), listed left-to-right by rows Checksum Sentence terminator MiLLennium Command Descriptions Manual Example $CLMA 0 0 5.113140990E+010 5.113140990E+010 5.810550069E+003, -1.07377180E+002, -1.41936974E+002 9.744136534E+004, 1.676933050E+003, -8.98776739E+004, 1.676933050E+003, 4.750666170E+002, -7.06077622E+002, -8.98776739E+004, -7.06077622E+002, 8.996728013E+004 *00 [CR][LF] 133 D Logs summary Example: $CLMA,0,0,5.113140990E+010,5.113140990E+010,5.810550069E+003, -1.07377180E+002,-1.41936974E+002,9.744136534E+004, 1.676933050E+003,-8.98776739E+004,1.676933050E+003, 4.750666170E+002,-7.06077622E+002,-8.98776739E+004, -7.06077622E+002,8.996728013E+004*00[CR][LF] CLMB Format: Field # 1 (header) 2 3 4 5 6-8 9 - 17 134 Message ID = 51 Message byte count = 132 Field Type Sync Checksum Message ID Message byte count Status of clock model (figure of quality) Number of rejected observations GPS time of last estimate GPS time of last update Parameters array (1x3 = 3 elements) Covariance matrix (3x3 = 9 elements), listed left-to-right by rows Bytes 3 1 4 4 4 4 8 8 3x8 9x8 Format char char integer integer integer integer double double double double Units Offset bytes 0 = good; -1 to -20 = bad observations seconds seconds [m m/s m] [ m2 m2/s 2 m /s m2/s2 m2/s m2 m2 m2/s m2 ] 0 3 4 8 12 16 20 28 36 60 MiLLennium Command Descriptions Manual D Logs summary COM1A/B and COM2A/B Pass-Through Logs There are two pass-through logs COM1A/B and COM2A/B, available on MiLLennium GPSCards. The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a specified port (COM1 or COM2) to any specified GPSCard port (COM1 or COM2). This capability, in conjunction with the SEND command, can allow the GPSCard to perform bi-directional communications with other devices such as a modem, terminal, or another GPSCard. Please see Chapter 5, Special Pass-Throgh Logs for more information. MiLLennium Command Descriptions Manual 135 D Logs summary DOPA/B Dilution of Precision The dilution of precision data is calculated using the geometry of only those satellites that are currently being tracked and used in the position solution by the GPSCard and updated once every 60 seconds or whenever a change in the constellation occurs. Therefore, the total number of data fields output by the log is variable, depending on the number of SVs tracking. Twelve is the maximum number of SV PRNs contained in the list. NOTE: If a satellite is locked out using the LOCKOUT command, it will still be shown in the PRN list, but is significantly deweighted in the DOP calculation. DOPA Structure: $DOPA week prn list Field # seconds *xx gdop pdop htdop hdop tdop # sats [CR][LF] Field type Data Description Example $DOPA 637 512473.00 2.9644 # sats prn list Log header GPS week number GPS seconds into the week Geometric dilution of precision - assumes 3-D position and receiver clock offset (all 4 parameters) are unknown Position dilution of precision - assumes 3-D position is unknown and receiver clock offset is known Horizontal position and time dilution of precision. Horizontal dilution of precision. Time dilution of precision - assumes 3-D position is known and only receiver clock offset is unknown Number of satellites used in position solution (0-12) PRN list of SV PRNs tracking (1-32), null field until first position solution available *xx [CR][LF] Checksum Sentence terminator 1 2 3 4 $DOPA week seconds gdop 5 pdop 6 7 8 htdop hdop tdop 9 10... variable variable 2.5639 2.0200 1.3662 1.4880 6 18,6,11,2,16, 19 *29 [CR][LF] Example: $DOPA,637,512473.00,2.9644,2.5639,2.0200,1.3662,1.4880,6,18,6,11,2,16,19 *29[CR][LF] 136 MiLLennium Command Descriptions Manual D Logs summary DOPB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11... Message ID = 07 Data Message byte count = 68+(sats*4) Bytes Format Sync 3 char Checksum 1 char Message ID 4 integer Message byte count 4 integer Week number 4 integer Seconds of week 8 double gdop 8 double pdop 8 double htdop 8 double hdop 8 double tdop 8 double Number of satellites used 4 integer 1st PRN 4 integer Next satellite PRN Offset = 68 + (sats*4) where sats = 0 to (number of sats-1) MiLLennium Command Descriptions Manual Units weeks seconds Offset 0 3 4 8 12 16 24 32 40 48 56 64 68 137 D Logs summary ETSA/B Extended Tracking Status These logs provide channel tracking status information for each of the GPSCard parallel channels. NOTE: This log is intended for status display only; since some of the data elements are not synchronized together, they are not to be used for measurement data. Please use the RGEA/B/D, SATA/B, and SVDA/B logs to obtain synchronized data for post processing analysis. If both the L1 and L2 signals are being tracked for a given PRN, two entries with the same PRN will appear in the tracking status logs. As shown in Table D-5 Receiver Self Test Status Codes these entries can be differentiated by bit 19, which is set if there are multiple observables for a given PRN, and bit 20, which denotes whether the observation is for L1 or L2. This is to aid in parsing the data. ETSA Structure: $ETSA prn sol status # obs week seconds ch-tr-status dopp C/No residual locktime psr reject code ch-tr-status dopp C/No residual locktime psr reject code : prn *xx [CR][LF] Field # Field type Data Description Example $ETSA 850 332087.00 1 2 3 $ETSA week seconds 4 5 6 7 sol status # obs prn ch-tr-status 8 9 10 11 12 dopp C/No residual locktime psr Log header GPS week number GPS seconds into the week (receiver time, not corrected for clock error, CLOCKADJUST enabled) Solution status (see Table D-1) Number of observations to follow Satellite PRN number (1-32) (channel 0) Hexadecimal number indicating channel tracking status (See Table D-7) Instantaneous carrier Doppler frequency (Hz) Carrier to noise density ratio (dB-Hz) Residual from position filter (m) Number of seconds of continuous tracking (no cycle slips) Pseudorange measurement (m) 13 14-21 .. 94-101 102 103 . reject code .. .. .. *xx [CR][LF] Indicates whether the range is valid (code = 0) or not (see Table D-11) Next PRN #,ch-tr-status,dopp,C/No,residual,locktime,psr,reject code .. Last PRN #,ch-tr-status,dopp,C/No,residual,locktime,psr,reject code Checksum Sentence terminator 138 0 24 7 00082E04 -613.5 54.682 27.617 12301.4 20257359.5 7 0 *19 [CR][LF] MiLLennium Command Descriptions Manual D Logs summary Example (carriage returns have been added between observations for clarity): $ETSA,850,332087.00,0,24, 7,00082E04,-613.5,54.682,27.617,12301.4,20257359.57,0, 7,00582E0B,-478.1,46.388,0.000,11892.0,20257351.96,13, 5,00082E14,3311.2,35.915,1.037,1224.4,24412632.47,0, 5,00582E1B,2580.4,39.563,0.000,1186.7,24412629.40,13, 9,00082E24,1183.1,53.294,-29.857,7283.8,21498303.67,0, 9,00582E2B,921.9,44.422,0.000,7250.2,21498297.13,13, 2,00082E34,-2405.2,50.824,-20.985,19223.6,22047005.47,0, 2,00582E3B,-1874.1,41.918,0.000,19186.7,22046999.44,13, 4,00082E44,3302.8,47.287,7.522,3648.1,22696783.36,0, 4,00582E4B,2573.6,37.341,0.000,3191.2,22696778.15,13, 14,00082E54,2132.7,41.786,-22.388,541.3,25117182.07,0, 14,00582E5B,1661.7,33.903,0.000,500.7,25117179.63,13, 26,00082E64,-3004.3,43.223,2.928,14536.2,25074382.19,0, 26,00582E6B,-2340.9,33.019,0.000,14491.7,25074378.01,13, 15,00082E74,-3037.7,43.669,0.508,12011.5,24104788.88,0, 15,00582E7B,-2367.0,34.765,0.000,11842.4,24104781.53,13, 24,00082E84,3814.0,37.081,7.511,95.7,25360032.49,0, 24,00582E8B,2972.0,24.148,0.000,5.2,25360030.13,13, 28,00082A90,-9800.9,0.000,0.000,0.0,0.00,9, 28,00382A90,-7637.0,0.000,0.000,0.0,0.00,9, 3,000822A0,-3328.3,0.000,0.000,0.0,0.00,9, 3,005828A0,-2593.5,0.000,0.000,0.0,0.00,9, 27,000822B0,-3851.7,0.000,0.000,0.0,0.00,9, 27,005828B0,-3001.7,0.000,0.000,0.0,0.00,9,*41[CR][LF] ETSB Format: Field # 1 (header) 2 3 4 5 Message ID = 48 Message byte count = 32 + (n x 52) where n is number of observations Data Sync Checksum Message ID Message byte count Week number Time of week Solution status(see Table D-1) Bytes char char integer integer integer double integer integer 4 4 8 8 integer integer double double 6 7 8 9 Number of observations PRN number (first observation) Channel tracking status (See Table D-7) Doppler C/N0 10 11 12 13 14 ... Residual 8 Locktime 8 Pseudorange 8 Rejection code(see Table D-11) 4 Offset = 32 + (#obs x 52) where #obs varies from 0 - 23 MiLLennium Command Descriptions Manual Format 3 1 4 4 4 8 4 4 double double double integer Units weeks seconds Hz dB-Hz metres seconds metres Offset 0 3 4 8 12 16 24 28 32 36 40 48 56 64 72 80 139 D Logs summary FRMA/B Framed Raw Navigation Data This message contains the raw framed navigation data. An individual message is sent for each PRN being tracked. The message is updated with each new frame, therefore it is best to log the data with the ‘onnew’ trigger activated. FRMA Structure: $FRMA *xx Field # week seconds prn cstatus # of bits framed raw data [CR][LF] Field type Data Description Example 1 $FRMA Log header $FRMA 2 week GPS week number 845 3 seconds GPS seconds into the week 238623.412 4 prn PRN of satellite from which data originated 120 5 cstatus Channel Tracking Status (see Table D-7) 80811F14 6 # of bits Number of bits transmitted in the message. 250 for WAAS, 300 for GPS and 85 for GLONASS. 250 7 framed raw data One field of raw framed navigation data. 9AFE5354656C2053796E636 8726F6E69636974792020202 020202020B0029E40*3F 8 *xx Checksum *42 9 [CR][LF] Sentence terminator [CR][LF] FRMB Format: Message ID = 54 Field # Message byte count = variable Data Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer 4 Message byte count 4 integer bytes 8 2 Week number 4 integer weeks 12 3 Seconds of week 8 double seconds 16 4 PRN number 4 integer 1-999 24 5 Channel Tracking Status (see Table D-7) 4 integer n/a 28 6 Number of Bits 4 integer 250 for WAAS 300 for GPS 85 for GLONASS 32 7 Data Sub-frame variable char N/A 36 140 MiLLennium Command Descriptions Manual D Logs summary GGAB Global Position System Fix Data (Binary Format Only) Time, position and fix-related data of the GPS receiver. This binary log is a replica of the NMEA GPGGA ASCII log expressed in binary format with NovAtel header added. Format: Message ID = 27 Field # Data 1 (header) Bytes Sync Checksum Message ID Message byte count UTC time of position Latitude (DDmm.mm) (+ is North, - is South) Longitude (DDDmm.mm) (+ is East, - is West) Fix status 0 = fix not available or invalid 1 = GPS fix 2 = Differential GPS fix Number of satellites in use. May be different to the number in view Horizontal dilution of precision Antenna altitude above/below mean-sea-level (geoid) Geoidal separation (see Figure C-6) 2 3 4 5 6 7 8 9 10 Age of Differential GPS data Differential reference station ID, 0000-1023 11 Note: Message byte count = 80 ➀ ➀ Format Units Offset 3 1 4 4 8 8 char char integer integer double double hhmmss.ss degrees 0 3 4 8 12 20 8 double degrees 28 4 integer 36 4 8 8 8 8 integer double double double double 40 44 52 60 68 4 integer metres metres seconds 76 The maximum age reported here is limited to 99 seconds. MiLLennium Command Descriptions Manual 141 D Logs summary GPALM Almanac Data This log outputs raw almanac data for each satellite PRN contained in the broadcast message. A separate record is logged for each PRN, up to a maximum of 32 records. Following a GPSCard reboot, no records will be output until new broadcast message data is received from a satellite. It takes a minimum of 12.5 minutes to collect a complete almanac following GPSCard boot-up. (The almanac reported here has no relationship to the NovAtel $ALMA almanac injection command. Following a cold start, the log will output null fields until a new almanac is collected from a satellite.) Structure: $GPALM # msg alm ref time omega msg # incl angle long asc node Field PRN Mo GPS wk SV hlth omegadot af1 rt axis *xx Structure ecc [CR][LF] Field Description 1 2 3 4 5 $GPALM # msg msg # PRN GPS wk Log header Total number of messages logged Current message number Satellite PRN number, 01 to 32 GPS reference week number 6 SV hlth 7 Symbol Example ➀ x.x x.x xx x.x $GPALM 17 17 28 653 SV health, bits 17-24 of each almanac page ➁ hh 00 ecc e, eccentricity ➂ hhhh 3EAF 8 alm ref time toa, almanac reference time ➂ hh 87 9 incl angle (sigma)i, inclination angle ➂ hhhh OD68 10 omegadot OMEGADOT, rate of right ascension ➂ hhhh FD30 11 rt axis (A)1/2, root of semi-major ➂ hhhhhh A10CAB 12 omega ➂ hhhhhh 6EE732 13 long asc node omega, argument of perigee (OMEGA)o,longitude of ascension node ➂ hhhhhh 525880 14 Mo Mo, mean anomaly ➂ hhhhhh 6DC5A8 15 af0 af0, clock parameter ➂ hhh 009 16 af1 ➂ hhh 005 17 18 *xx [CR][LF] af1, clock parameter Checksum Sentence terminator *hh *37 [CR][LF] axis Example: $GPALM,17,17,28,653,00,3EAF,87,0D68,FD30,A10CAB,6EE732,525880,6DC5A8,009, 005*37[CR][LF] ➀ Variable length integer, 4-digits maximum from (2) most significant binary bits of Subframe 1, Word 3 reference Table 20-I, ICD-GPS-200, Rev. B, and (8) least significant bits from subframe 5, page 25, word 3 reference Table 20-I, ICD-GPS-200, Rev. B, paragraph 20.3.3.5.1.7 ➁ Reference paragraph 20.3.3.5.1.3, Table 20-VII and Table 20-VIII, ICD-GPS-200, Rev. B ➂ Reference Table 20-VI, ICD-GPS-200, Rev. B for scalingfactors and units. To obtain copies of ICD-GPS- 200, see Appendix F, Standards and References, for address information. 142 MiLLennium Command Descriptions Manual D Logs summary GPGGA Global Position System Fix Data Time, position and fix-related data of the GPS receiver. The information contained in this log is also available in the NovAtel GGAB log in binary format. This log will output all null data fields until the GPSCard has achieved first fix. Structure: $GPGGA alt utc lat units null Field Structure 1 2 3 4 5 6 7 $GPGGA utc lat lat dir lon lon dir GPS qual 8 9 10 11 12 13 14 15 16 17 # sats hdop alt units null null age stn ID *xx [CR][LF] ➀ lat dir null age lon lon dir stn ID *xx GPS qual # sats hdop [CR][LF] Field Description Log header UTC time of position (hours/minutes/seconds/ decimal seconds) Latitude (DDmm.mm) Latitude direction (N = North, S = South) Longitude (DDDmm.mm) Longitude direction (E = East, W = West) GPS Quality indicator 0= fix not available or invalid 1= GPS fix 2= Differential GPS fix Number of satellites in use (00-12). May be different to the number in view Horizontal dilution of precision Antenna altitude above/below mean sea level (geoid) Units of antenna altitude (M = metres) (This field not available on GPSCards) (This field not available on GPSCards) Age of Differential GPS data (in seconds) ➀ Differential reference station ID, 0000-1023 Checksum Sentence terminator Symbol Example hhmmss.ss llll.ll a yyyyy.yy a x $GPGGA 220147.50 5106.7194489 N 11402.3589020 W 1 xx x.x x.x M xx xxxx *hh 08 0.9 1080.406 M ,, ,, ,, ,, *48 [CR][LF] The maximum age reported here is limited to 99 seconds. Example: $GPGGA,220147.50,5106.7194489,N,11402.3589020,W,1,08,0.9,1080.406,M,,,, *48[CR][LF] MiLLennium Command Descriptions Manual 143 D Logs summary GPGLL Geographic Position Latitude and longitude of present vessel position, time of position fix, and status. This log will output all null data fields until the GPSCard has achieved first fix. Structure: $GPGLL Field lat lat dir Structure 1 2 3 4 5 6 $GPGLL lat lat dir lon lon dir utc 7 8 9 data status *xx [CR][LF] lon lon dir utc data status Field Description Symbol Log header Latitude (DDmm.mm) Latitude direction (N = North, S = South) Longitude (DDDmm.mm) Longitude direction (E = East, W = West) UTC time of position (hours/minutes/seconds/decimal seconds) Data status: A = Data valid, V = Data invalid Checksum Sentence terminator llll.ll a yyyyy.yy a hhmmss.ss A *hh *xx [CR][LF] Example $GPGLL 5106.7198674 N 11402.3587526 W 220152.50 A *1B [CR][LF] Example: $GPGLL,5106.7198674,N,11402.3587526,W,220152.50,A*1B[CR][LF] 144 MiLLennium Command Descriptions Manual D Logs summary GPGRS GPS Range Residuals for Each Satellite Range residuals can be computed in two ways, and this log reports those residuals. Under mode 0, residuals output in this log are used to update the position solution output in the GPGGA message. Under mode 1, the residuals are re-computed after the position solution in the GPGGA message is computed. The GPSCard computes range residuals in mode 1. An integrity process using GPGRS would also require GPGGA (for position fix data), GPGSA (for DOP figures), and GPGSV (for PRN numbers) for comparative purposes. Structure: $GPGRS utc mode res res res res *xx [CR][LF] Field Structure 1 2 3 $GPGRS utc mode 4 - 15 res 16 17 *xx [CR][LF] res res res res res Field Description Log header UTC time of position (hours/minutes/seconds/ decimal seconds) Mode 0 =residuals were used to calculate the position given in the matching GGA line (apriori) (not used by GPSCard) Mode 1 =residuals were recomputed after the GGA position was computed (preferred mode) Range residuals for satellites used in the navigation solution. Order matches order of PRN numbers in GPGSA. Checksum Sentence terminator res Symbol hhmmss.ss x x.x,x.x,..... *hh res res Example $GPGRS 192911.0 1 -13.8,-1.9,11.4,-33.6,0.9, 6.9,-12.6,0.3,0.6, -22.3 *65 [CR][LF] Example: $GPGRS,192911.0,1,-13.8,-1.9,11.4,-33.6,0.9,6.9,-12.6,0.3,0.6,-22.3,, *65[CR][LF] NOTE: If the range residual exceeds ± 99.9, then the decimal part will be dropped. Maximum value for this field is ± 999. The sign of the range residual is determined by the order of parameters used in the calculation as follows: range residual = calculated range - measured range. MiLLennium Command Descriptions Manual 145 D Logs summary GPGSA GPS GPS DOP and Active Satellites receiver operating mode, satellites used for navigation and DOP values. Structure: $GPGSA mode MA prn prn prn pdop hdop vdop Field Structure 1 2 $GPGSA mode MA 3 4 - 15 mode 123 prn 16 17 18 19 20 pdop hdop vdop *xx [CR][LF] mode 123 prn *xx prn prn prn prn prn prn prn prn [CR][LF] Field Description Symbol Log header A = Automatic 2D/3D (not used by GPSCard) M = Manual, forced to operate in 2D or 3D Mode: 1 = Fix not available; 2 = 2D; 3 = 3D PRN numbers of satellites used in solution (null for unused fields), total of 12 fields Position dilution of precision Horizontal position and time dilution of precision Vertical dilution of precision Checksum Sentence terminator M x xx,xx,..... x.x x.x x.x *hh Example $GPGSA M 3 18,03,13,25,16, 24,12,20,,,, 1.5 0.9 1.2 *3F [CR][LF] Example: $GPGSA,M,3,18,03,13,25,16,24,12,20,,,,,1.5,0.9,1.2*3F[CR][LF] 146 MiLLennium Command Descriptions Manual D Logs summary GPGST Pseudorange Measurement Noise Statistics Pseudorange measurement noise statistics are translated in the position domain in order to give statistical measures of the quality of the position solution. 10 Structure: $GPGST orient Field utc rms lat std smjr std smnr std lon std alt std Structure 1 2 3 $GPGST utc rms 4 5 6 7 8 9 10 11 smjr std smnr std orient lat std lon std alt std *xx [CR][LF] *xx [CR][LF] Field Description Log header UTC time of position (hours/minutes/seconds/ decimal seconds) RMS value of the standard deviation of the range inputs to the navigation process. Range inputs include pseudoranges and DGPS corrections. Standard deviation of semi-major axis of error ellipse (metres) Standard deviation of semi-minor axis of error ellipse (metres) Orientation of semi-major axis of error ellipse (degrees from true north) Standard deviation of latitude error (metres) Standard deviation of longitude error (metres) Standard deviation of altitude error (metres) Checksum Sentence terminator Symbol Example hhmmss.ss x.x $GPGST 192911.0 28.7 x.x x.x x.x x.x x.x x.x *hh 21.6 12.0 20.4 20.7 13.6 11.9 *51 [CR][LF] Example: $GPGST,192911.0,28.7,21.6,12.0,20.4,20.7,13.6,11.9*51[CR][LF] MiLLennium Command Descriptions Manual 147 D Logs summary GPGSV GPS Satellites in View Number of SVs in view, PRN numbers, elevation, azimuth and SNR value. Four satellites maximum per message. When required, additional satellite data sent in second or third message. Total number of messages being transmitted and the current message being transmitted are indicated in the first two fields. NOTES: Satellite information may require the transmission of multiple messages. The first field specifies the total number of messages, minimum value 1. The second field identifies the order of this message (messagenumber), minimum value 1. A variable number of 'PRN-Elevation-Azimuth-SNR' sets are allowed up to a maximum of four sets per message. Null fields are not required for unused sets when less than four sets are transmitted. GPGSV logs will not output until time of first fix. Structure: $GPGSV prn # msg msg # # sats elev azimuth SNR prn elev azimuth SNR *xx [CR][LF] : Field Structure Field Description Symbol 1 2 3 4 5 6 7 8 $GPGSV # msg msg # # sats prn elev azimuth SNR Log header Total number of messages, 1 to 3 Message number, 1 to 3 Total number of satellites in view Satellite PRN number Elevation, degrees, 90¡ maximum Azimuth, degrees True, 000 to 359 SNR (C/N0) 00-99 dB, null when not tracking ... ... ... variable variable ... ... ... *xx [CR][LF] Next satellite PRN number, elev, azimuth, SNR, ... Last satellite PRN number, elev, azimuth, SNr, Checksum Sentence terminator x x xx xx xx xxx xx *hh Example $GPGSV 3 1 09 03 51 140 42 *72 [CR][LF] Example: $GPGSV,3,1,09,03,51,140,42,16,02,056,40,17,78,080,42,21,25,234,00*72[CR][LF] $GPGSV,3,2,09,22,19,260,00,23,59,226,00,26,45,084,39,27,07,017,39*78[CR][LF] $GPGSV,3,3,09,28,29,311,44*42[CR][LF] 148 MiLLennium Command Descriptions Manual D Logs summary GPRMB Navigation Information Navigation data from present position to a destination waypoint. The destination is set active by the GPSCard SETNAV command. If SETNAV has been set, a command to log either GPRMB or GPRMC will cause both logs to output data. Structure: $GPRMB data status dest ID dest lat lat dir range bearing vel Field xtrack dir dest lon arr status Structure origin ID lon dir *xx [CR][LF] Field Description 1 2 3 $GPRMB data status xtrack Log header Data status: A = data valid; V = navigation receiver warning 4 dir Direction to steer to get back on track (L/R) 5 origin ID Origin waypoint ID 6 dest ID Destination waypoint ID 7 dest lat Destination waypoint latitude (DDmm.mm 8 lat dir Latitude direction (N = North, S = South) 9 dest lon Destination waypoint longitude (DDDmm.mm) 10 lon dir Longitude direction (E = East, W = West) 11 range Range to destination, nautical miles 12 13 14 bearing vel arr status 15 16 *xx [CR][LF] Bearing to destination, degrees True Destination closing velocity, knots Arrival status: A = perpendicular passed V = destination not reached or passed Checksum Sentence terminator Cross track error ➀ ➁ ➂ ➂ ➂ ➂ ➂ ➂ ➃ Symbol Example A x.x $GPRMB V 0.011 a L c--c START c--c END llll.ll a 5106.7074 000 N yyyyy.yy 11402.349 a E x.x 0.0127611 x.x x.x A 153.093 0.3591502 V *hh *13 [CR][LF] Example: $GPRMB,V,0.011,L,START,END,5106.7074000,N,11402.3490000,W,0.0127611,153093, 0.3591502,V*13[CR][LF] ➀ - If cross track error exceeds 9.99 NM, display 9.99 - Represents track error from intended course - one nautical mile = 1,852 metres ➁ Direction to steer is based on the sign of the crosstrack error, i.e., L = xtrack error (+); R = xtrack error (–) ➂ Fields 5, 6, 7, 8, 9, and 10 are tagged from the GPSCard SETNAV command. ➃ If range to destination exceeds 999.9 NM, display 999.9 MiLLennium Command Descriptions Manual 149 D Logs summary GPRMC GPS Specific Information Time, date, position, track made good and speed data provided by the GPS navigation receiver. RMC and RMB are the recommended minimum navigation data to be provided by a GPS receiver. This log will output all null data fields until the GPSCard has achieved first fix. Structure: lat dir $GPRMC lon utc pos status lon dir speed Kn mag var var dir Field Structure *xx lat lat dir track true date [CR][LF] Field Description 1 2 3 $GPRMC utc pos status 4 5 6 7 8 9 10 11 lat lat dir lon lon dir speed Kn track true date mag var Log header UTC of position Position status: A = data valid V = data invalid Latitude (DDmm.mm) Latitude direction (N = North, S = South) Longitude (DDDmm.mm) Longitude direction (E = East, W = West) Speed over ground, knots Track made good, degrees True Date: dd/mm/yy ➀ Magnetic variation, degrees 12 13 14 var dir *xx [CR][LF] Magnetic variation direction E/W➁ Checksum Sentence terminator Symbol Example hhmmss.ss A $GPRMC 220216.50 A llll.ll a yyyyy.yy a x.x x.x xxxxxx x.x 5106.7187663 N 11402.3581636 W 0.3886308 130.632 150792 0.000 a *hh E *4B [CR][LF] Example: $GPRMC,220216.50,A,5106.7187663,N,11402.3581636,W,0.3886308,130.632,150792, 0.000,E*4B[CR][LF] ➀ Easterly variation (E) subtracts from True course Westerly variation (W) adds to True course ➁ Note that this field is the actual magnetic variation East or West and is the inverse sign of the value entered into the MAGVAR command. See MAGVAR in Appendix C for more information. 150 MiLLennium Command Descriptions Manual D Logs summary GPVTG Track Made Good And Ground Speed The track made good and speed relative to the ground. Structure: $GPVTG N track true speed km Field T track mag K *xx $GPVTG track true T track mag 5 6 7 8 9 10 11 M speed Kn N speed Km K *xx [CR][LF] speed Km [CR][LF] Structure 1 2 3 4 M Field Description Symbol Example x.x T x.x $GPVTG 24.168 T 24.168 Log header Track made good, degrees True True track indicator Track made good, degrees Magnetic; Track mag = Track true + (MAGVAR correction) See the MAGVAR command. Magnetic track indicator Speed over ground, knots Nautical speed indicator (N = Knots) Speed, kilometres/hour Speed indicator (K = km/hr) Checksum Sentence terminator M x.x N x.x K *hh M 0.4220347 N 0.781608 K *7A [CR][LF] Example: $GPVTG,24.168,T,24.168,M,0.4220347,N,0.781608,K*7A[CR][LF] MiLLennium Command Descriptions Manual 151 D Logs summary GPZDA UTC Time and Date This log will output all null data fields until the GPSCard has achieved first fix. Structure: $GPZDA utc day month NULL NULL *xx [CR][LF] Field 1 2 3 4 5 6 7 8 9 Structure $GPZDA utc day month year null null *xx [CR][LF] year Field Description Symbol Log header UTC time Day, 01 to 31 Month, 01 to 12 Year Local zone description - not available Local zone minutes description - not available Checksum Sentence terminator ➀ hhmmss.ss xx xx xxxx xx xx *hh Example $GPZDA 220238.00 15 07 1992 ,, ,, *6F [CR][LF] Example: $GPZDA,220238.00,15,07,1992,00,00*6F[CR][LF] ➀ 152 Local time zones are not supported by the GPSCard. Fields 6 and 7 will always be null. MiLLennium Command Descriptions Manual D Logs summary GPZTG UTC & Time to Destination Waypoint This log reports time to destination waypoint. Waypoint is set using the GPSCard SETNAV command. If destination waypoint has not been set with SETNAV, time-to-go and destination waypoint ID will be null. This log will output all null data fields until the GPSCard has achieved first fix. Structure: $GPZTG Field 1 2 3 4 5 6 utc time Structure $GPZTG utc time dest ID *xx [CR][LF] dest ID *xx [CR][LF] Field Description Log header UTC of position Time to go (995959.00 maximum reported) Destination waypoint ID Checksum Sentence terminator Symbol hhmmss.ss hhmmss.ss c--c *hh Example $GPZTG 220245.00 994639.00 END *36 [CR][LF] Example: $GPZTG,220245.00,994639.00,END*36[CR][LF] MiLLennium Command Descriptions Manual 153 D Logs summary MKPA/B Mark Position This log contains the estimated position of the antenna at detected mark impulse. It uses the last valid position and velocities to extrapolate the position at time of mark. Refer to the GPSCard Installation and Operating Manual Appendix for Mark Input pulse specifications. The latched time of mark impulse is in GPS weeks and seconds into the week. The resolution of the latched time is 49 ns. MKPA Structure: $MKPA week lat std Field # seconds lon std lat hgt std Field type 1 2 3 $MKPA week seconds 4 lat 5 lon 6 7 8 9 10 11 12 13 14 hgt undulation datum ID lat std lon std hgt std sol status *xx [CR][LF] lon hgt undulation sol status *xx datum ID [CR][LF] Data Description Example Log header GPS week number GPS seconds into the week measured from the receiver clock, coincident with the time of electrical closure on the Mark Input port. Latitude of position in current datum, in degrees/decimal degrees (DD.dddddddd), where a negative sign implies South latitude Longitude of position in current datum, in degrees/decimal degrees (DDD.dddddddd), where a negative sign implies West longitude Height of position in current datum, in metres with respect to MSL Geoid undulation, in metres (see Figure C-6) Current datum (see Table G-2 in Appendix G) I.D. # Standard deviation of latitude solution element, in metres Standard deviation of longitude solution element, in metres Standard deviation of height solution element, in metres Solution status as listed in Table D-1 Checksum Sentence terminator $MKPA 653 338214.773382 376 51.11227014 -114.03907552 1003.799 -16.199 61 7.793 3.223 34.509 0 *3C [CR][LF] Example: $MKPA,653,338214.773382376,51.11227014,-114.03907552,1003.799,-16.199,61, 7.793,3.223,34.509,0*3C[CR][LF] MKPB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 154 Message ID = 05 Data Sync Checksum Message ID Message byte count Week number Seconds of week Latitude Longitude Height Undulation Datum ID StdDev of latitude StdDev of longitude StdDev of height Solution status Message byte count = 88 Bytes 3 1 4 4 4 8 8 8 8 8 4 8 8 8 4 Format char char integer integer integer double double double double double integer double double double integer Units weeks seconds degrees (+ is North, - is South) degrees (+ is East, - is West) metres with respect to MSL metres metres metres metres Offset 0 3 4 8 12 16 24 32 40 48 56 60 68 76 84 MiLLennium Command Descriptions Manual D Logs summary MKTA/B Time of Mark Input This log contains the time of the detected Mark Input pulse leading edge as detected at the Mark Input I/O port. The resolution of this measurement is 49ns. Refer to the GPSCard Installation and Operating Manual Appendix for the Mark Input pulse specifications. MKTA Structure: $MKTA week utc offset Field # seconds offset offset std cm status *xx [CR][LF] Field type 1 2 3 $MKTA week seconds 4 offset 5 6 offset std utc offset 7 cm status 8 9 *xx [CR][LF] Data Description Example Log header GPS week number Seconds into the week as measured from the receiver clock, coincident with the time of electrical closure on the Mark Input port. Receiver clock offset, in seconds. A positive offset implies that the receiver clock is ahead of GPS Time. To derive GPS time, use the following formula: GPS time = receiver time - (offset) Standard deviation of receiver clock offset, in seconds This field represents the offset of GPS time from UTC time, computed using almanac parameters. To reconstruct UTC time, algebraically subtract this correction from field 3 above (GPS seconds). UTC time = GPS time - (utc offset) $MKTA 653 338214.773382376 Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that the model is in the process of stabilization Checksum Sentence terminator 0 0.000504070 0.000000013 -8.000000000 *05 [CR][LF] Example: $MKTA,653,338214.773382376,0.000504070,0.000000013,-8.000000000,0 *05[CR][LF] MKTB Format: Field # 1 (header) 2 3 4 5 6 7 Message ID = 04 Message byte count = 52 Data Sync Checksum Message ID Message byte count Week number Seconds of week Clock offset StdDev clock offset UTC offset Clock model status Bytes 3 1 4 4 4 8 8 8 8 4 MiLLennium Command Descriptions Manual Format char char integer integer integer double double double double integer Units weeks seconds seconds seconds seconds Offset 0 3 4 8 12 16 24 32 40 48 155 D Logs summary NAVA/B Waypoint Navigation Data This log reports the status of your waypoint navigation progress. It is used in conjunction with the command. REMEMBER: SETNAV The SETNAV command must be enabled before valid data will be reported from this log. NAVA Structure: $NAVA week seconds etas nav status Field # Field type 1 2 3 4 $NAVA week seconds distance 5 bearing 6 along track 7 xtrack 8 etaw 9 etas 10 11 12 13 nav status sol status *xx [CR][LF] distance sol status *xx bearing along track xtrack etaw [CR][LF] Data Description Example Log header GPS week number GPS seconds into the week Straight line horizontal distance from current position to the destination waypoint, in metres (see SETNAV command, Appendix C; Figure C-5). This value is positive when approaching the waypoint and becomes negative on passing the waypoint. Direction from the current position to the destination waypoint in degrees with respect to True North (or Magnetic if corrected for magnetic variation by MAGVAR command) Horizontal track distance from the current position to the closest point on the waypoint arrival perpendicular; expressed in metres. This value is positive when approaching the waypoint and becomes negative on passing the waypoint. The horizontal distance (perpendicular track-error) from the vessel's present position to the closest point on the great circle line that joins the FROM and TO waypoints. If a "track offset" has been entered in the SETNAV command, xtrack will be the perpendicular error from the "offset track". Xtrack is expressed in metres. Positive values indicate the current position is right of the Track, while negative offset values indicate left. Estimated GPS week number at time of arrival at the "TO" waypoint along-track arrival perpendicular based on current position and speed, in units of GPS weeks. If the receiving antenna is moving at a speed of less than 0.1 m/sec in the direction of the destination, the value in this field will be"9999". Estimated GPS seconds into week at time of arrival at destination waypoint along-track arrival perpendicular, based on current position and speed, in units of GPS seconds into the week. If the receiving antenna is moving at a speed of less than 0.1 m/sec in the direction of the destination, the value in this field will be"0.000". Navigation data status, where 0 = good, 1 = no velocity, and 2 = bad navigation calculation Solution status as listed in Table D-1 Checksum Sentence terminator $NAVA 640 333115.00 6399.6305 88.017 6396.9734 184.3929 657 51514.000 0 1 *11 [CR][LF] Example: $NAVA,640,333115.00,6399.6305,88.017,6396.9734,184.3929,657,51514.000,0,1 *11[CR][LF] NOTE: All distances and angles are calculated using Vincenty's long line geodetic equations that operate on the currently selected user datum. See Figure D-1 for an illustration of navigation parameters. 156 MiLLennium Command Descriptions Manual D Logs summary NAVB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 Message ID = 08 Data Sync Checksum Message ID Message byte count Week number Seconds of week Distance Bearing Along track Xtrack ETA week ETA seconds NAV status where 0 = good 1 = no velocity 2 = bad navigation Solution status Message byte count = 76 Bytes Format 3 1 4 4 4 8 8 8 8 8 4 8 4 char char integer integer integer double double double double double integer double integer 4 integer MiLLennium Command Descriptions Manual Units weeks seconds metres degrees metres metres weeks seconds Offset 0 3 4 8 12 16 24 32 40 48 56 60 68 72 157 D Logs summary Figure D-1 Example of Navigation Parameters A = FROM lat-lon B = TO lat-lon AB = Great circle line drawn between FROM A lat-lon and TO B lat-lon AC = Track offset from A to C BD = Track offset from B to D CD = Offset track to steer (parallel to AB) F = Current GPS position FD = Current distance and bearing from F to D E = Xtrack perpendicular reference point EF = Xtrack error from E to F (perpendicular to CD) FG = Along track from F to G (perpendicular to BD) AB - True bearing = 70° AB - Magnetic bearing = True + (MAGVAR correction) = 70° + (-20) = 50° 158 MiLLennium Command Descriptions Manual D Logs summary PAVA/B Position Averaging Status These logs are meant to be used in conjunction with the POSAVE command. If the POSAVE command has not been issued, all fields in the PAVA/B logs except week and seconds will be zero. However, when position averaging is underway, the various fields contain the parameters being used in the position averaging process. The log trigger ONCHANGED is recommended, but ONTIME can also be used. See the description of the POSAVE command. See also Appendix A, Section A.3.2 Pseudorange Algorithms. NOTE: All quantities are referenced to the WGS84 ellipsoid, regardless of the use of the DATUM or USERDATUM commands, except for the height parameter (field 6). The relation between the geoid and the WGS84 ellipsoid is the geoidal undulation, and can be obtained from the POSA/B logs. PAVA Structure : $PAVA week seconds lat lng hgt sdlat sdlng sdhgt time samples *xx Field # 1 2 3 4 5 6 7 8 9 10 11 12 13 Field type $PAVA week seconds lat lng hgt sdlat sdlng sdhgt time samples *xx [CR][LF] [CR][LF] Data Description Example Log header GPS week number GPS seconds into the week Average WGS84 latitude (degrees) Average WGS84 longitude (degrees) Average height above sea level, or geoid (m) Estimated standard deviation of the average latitude (m) Estimated standard deviation of the average longitude (m) Estimated standard deviation of the average height (m) Elapsed time of averaging (s) Number of samples in the average Checksum Sentence terminator $PAVA 846 145872.00 51.11381167 -114.04356455 1068.100 26.2 12.1 54.9 7 1 *0C [CR][LF] Example: $PAVA,846,145872.00,51.11381167,-114.04356455,1068.100,26.2,12.1,54.9,7,1*0C [CR][LF] MiLLennium Command Descriptions Manual 159 D Logs summary PAVB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 160 Message ID = 50 Message byte count = 80 Data Sync Checksum Message ID Message byte count GPS week number GPS seconds into the week Average WGS84 latitude Average WGS84 longitude Average height above sea level Estimated standard deviation of the average latitude Estimated standard deviation of the average longitude Estimated standard deviation of the average height Elapsed time of averaging Number of samples in the average Bytes Format Units Offset 3 1 4 4 4 8 8 8 8 8 char char integer integer integer double double double double double weeks seconds degrees degrees metres metres 0 3 4 8 12 16 24 32 40 48 8 double metres 56 8 double metres 64 4 4 integer integer seconds 72 76 MiLLennium Command Descriptions Manual D Logs summary POSA/B Computed Position This log will contain the last valid position and time calculated referenced to the GPSAntenna phase centre. The position is in geographic coordinates in degrees based on your specified datum (default is WGS84). The height is referenced to mean sea level. The receiver time is in GPS weeks and seconds into the week. The estimated standard deviations of the solution and current filter status are also included. See also Appendix A, Section A.3.2 Pseudorange Algorithms. POSA Structure: $POSA week lat std Field # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 seconds lon std lat hgt std lon hgt sol status undulation *xx datum ID [CR][LF] Type Data Description Example $POSA week seconds lat lon hgt undulation datum ID lat std lon std hgt std sol status *xx [CR][LF] Log header GPS week number GPS seconds into the week Latitude of position in current datum, in degrees (DD.dddddddd). A - implies South latitude Longitude of position in current datum, in degrees (DDD.dddddddd). A + implies West longitude Height of position in current datum, in metres with respect to mean sea level (see Figure D-2) Geoidal separation, in metres, where + is above spheroid and - is below spheroid (see Figure C-6) Current datum ID # (see Table G-2 in Appendix G) Standard deviation of latitude solution element, in metres Standard deviation of longitude solution element, in metres Standard deviation of height solution element, in metres Solution status as listed in Table D-1 Checksum Sentence terminator $POSA 637 511251.00 51.11161847 -114.03922149 1072.436 -16.198 61 26.636 6.758 78.459 0 *12 [CR][LF] Example: $POSA,637,511251.00,51.11161847,-114.03922149,1072.436,-16.198,61,26.636, 6.758,78.459,0*12[CR][LF] POSB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 Message ID = 01 Message byte count = 88 Data Sync Checksum Message ID Message byte count Week number Seconds of week Latitude Longitude Height Undulation Datum ID StdDev of latitude StdDev of longitude StdDev of height Solution status Bytes 3 1 4 4 4 8 8 8 8 8 4 8 8 8 4 MiLLennium Command Descriptions Manual Format char char integer integer integer double double double double double integer double double double integer Units weeks seconds degrees (+ is North, - is South) degrees (+ is East, - is West) metres with respect to MSL metres metres metres metres Offset 0 3 4 8 12 16 24 32 40 48 56 60 68 76 84 161 D Logs summary PRTKA/B Computed Position (RTK) This log contains the best available position computed by the receiver, along with three status flags. In addition, it reports other status indicators, including differential lag, which is useful in predicting anomalous behaviour brought about by outages in differential corrections. This log replaces the P20A log; it is similar, but adds extended status information. With the system operating in an RTK mode, this log will reflect the latest low-latency solution for up to 30 seconds after reception of the last reference station observations. After this 30 second period, the position reverts to the best solution available; the degradation in accuracy is reflected in the standard deviation fields, and is summarized in Chapter 1, Table 1-2. If the system is not operating in an RTK mode, pseudorange differential solutions continue for 60 seconds after loss of the data link, though a different value can be set using the DGPSTIMEOUT command. PRTKA Structure: $PRTKA week L1L2 #high lat σ lon σ posn type Field # Field type 1 2 3 4 5 6 $PRTKA week sec lag #sv #high 7 8 L1L2 #high lat 9 lon 10 11 12 13 14 15 16 17 18 19 20 21 22 hgt undulation datum ID lat σ lon σ hgt σ soln status rtk status posn type idle stn ID *xx [CR][LF] 162 lat idle sec lag #sv lon hgt undulation hgt σ stn ID soln status *xx #high datum ID rtk status [CR][LF] Data Description Log header GPS week number GPS time into the week (in seconds) Differential lag in seconds Number of matched satellites; may differ from the number in view. Number of matched satellites above RTK mask angle; observations from satellites below mask are heavily de-weighted Number of matched satellites above RTK mask angle with both L1 and L2 available Latitude of position in current datum, in decimal fraction format. A negative sign implies South latitude Longitude of position in current datum, in decimal fraction format. A negative sign implies West longitude Height of position in current datum, in metres above mean sea level Geoidal separation, in metres, where(+ve) is above ellipsoid and (-ve) is below ellipsoid Current datum (see Appendix G) Standard deviation of latitude solution element, in metres Standard deviation of longitude solution element, in metres Standard deviation of height solution element, in metres Solution status (see Table D-1) RTK status (see Tables D-3, D-4) Position type (see Table D-2) Percent idle time, percentage Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Checksum Sentence terminator Example $PRTKA 872 174963.00 1.000 8 7 7 51.11358042429 -114.04358006710 1059.4105 -16.2617 61 0.0096 0.0100 0.0112 0 0 4 42 119 *51 [CR][LF] MiLLennium Command Descriptions Manual D Logs summary Example: $PRTKA,872,174963.00,1.000,8,7,7,51.11358042429, -114.04358006710,1059.4105, -16.2617,61,0.0096,0.0100,0.0112,0,0,4,42,119*51[CR][LF] PRTKB Format: Message ID = 63 Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Message byte count = 124 Data Sync Checksum Message ID Message byte count Week number GPS time into the week Differential lag Number of matched satellites (00-12) Number of matched satellites above RTK mask angle Number of matched satellites above RTK mask angle with both L1 and L2 available Latitude Longitude Height above mean sea level Undulation Datum ID Standard deviation of latitude Standard deviation of longitude Standard deviation of height Solution status RTK status Position type Idle Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) MiLLennium Command Descriptions Manual Bytes Format Units 3 1 4 4 4 8 8 4 4 char char integer integer integer double integer integer 0 3 4 8 12 16 24 32 36 4 integer 40 8 8 8 8 4 8 8 8 4 4 4 4 4 double double double double integer double double double integer integer integer integer integer weeks seconds seconds degrees degrees metres metres metres metres metres Offset 44 52 60 68 76 80 88 96 104 108 112 116 120 163 D Logs summary PVAA/B XYZ Position, Velocity and Acceleration The PVAA/B logs contain the receiver’s latest computed position, velocity and acceleration in ECEF coordinates. The position, velocity and acceleration status fields indicate whether or not the corresponding data are valid. This command supports INS (Inertial Navigation System) integration. PVA logs can be injected into the receiver from an INS. This information is only used by the tracking loops of the receiver to aid in reacquisition of satellites after loss of lock, otherwise it is ignored. This command is only useful for very high dynamics where expected velocity changes during the signal blockage of more than 100 metres per second can occur. NOTE: These quantities are always referenced to the WGS84 ellipsoid, regardless of the use of the DATUM or commands. USERDATUM PVAA Structure: $PVAA A-x week A-y Field # A-z Field type seconds P-x P-status V-status P-y Data Description P-z V-x A-status V-y V-z *xx [CR][LF] Example 1 2 3 4 5 6 7 8 9 10 $PVAA week seconds P-x P-y P-z V-x V-y V-z A-x Log header GPS week number GPS time of week (s) Position’s X-coordinate (m) Position’s Y-coordinate (m) Position’s Z-coordinate (m) Velocity vector along X-axis (m/s) Velocity vector along Y-axis (m/s) Velocity vector along Z-axis (m/s) Acceleration vector along X-axis (m/s2) $PVAA 845 344559.00 -1634953.141 -3664681.855 4942249.361 -0.025 0.140 0.078 0.000 11 A-y Acceleration vector along Y-axis (m/s2) -0.000 12 A-z 0.000 13 14 15 16 17 P-status V-status A-status *xx [CR][LF] Acceleration vector along Z-axis (m/s2) Position status (0 = bad; 1 = good) Velocity status (0 = bad; 1 = good) Acceleration status (0 = bad; 1 = good) Checksum Sentence terminator 1 1 1 *02 [CR][LF] Example: $PVAA,845,344559.00,-1634953.141,-3664681.855,4942249.361,-0.025,0.140, 0.078,0.000,-0.000,0.000,1,1,1*02 164 MiLLennium Command Descriptions Manual D Logs summary PVAB Format: Field # 1 (header) Message ID = 49 Message byte count = 108 Field Type Bytes Format 2 3 4 5 6 7 8 9 10 Sync Checksum Message ID Message byte count GPS week number GPS time of week Position vector along X-axis Position vector along Y-axis Position vector along Z-axis Velocity vector along X-axis Velocity vector along Y-axis Velocity vector along Z-axis Acceleration vector along X-axis 3 1 4 4 4 8 8 8 8 8 8 8 8 char char integer integer integer double double double double double double double double 11 Acceleration vector along Y-axis 8 12 Acceleration vector along Z-axis 8 Offset m/s2 0 3 4 8 12 16 24 32 40 48 56 64 72 double m/s2 80 double m/s2 88 13 Position status ➀ 4 integer 14 Velocity status ➀ 4 integer 15 Acceleration status ➀ 4 integer ➀ Only the least-significant bit is used for this flag; the others are reserved for future use. MiLLennium Command Descriptions Manual Units weeks seconds metres metres metres m/s m/s m/s 96 100 104 165 D Logs summary PXYA/B Computed Cartesian Coordinate Position This log contains the last valid position, expressed in Cartesian x-y-z space coordinates, relative to the center of the Earth. The positions expressed in this log are always relative to WGS84 regardless of the setting of the DATUM or USERDATUM command. See Figure D-2 for a definition of the coordinates. PXYA Structure: $PXYA week fix status Field # x diff lag *xx y z x std y std $PXYA week seconds x y z x std y std z std sol status fix status 12 diff lag *xx [CR][LF] ➀ z std sol status [CR][LF] Field type 1 2 3 4 5 6 7 8 9 10 11 13 14 seconds Data Description Example Log header GPS week number GPS seconds into the week Position x coordinate, in metres Position y coordinate, in metres Position z coordinate, in metres Standard deviation of x, in metres Standard deviation of y, in metres Standard deviation of z, in metres Solution status as listed in Table D-1 0= fix not available or invalid 1= Single point standalone fix 2= Differential fix Age of differential correction (seconds) (= 0 if fix status ≠ 2) $PXYA 713 488150.00 -1634756.995 -3664965.028 4942151.391 2.335 3.464 4.156 0 2 Checksum Sentence terminator *08 [CR][LF] 0.4 ➀ This log provides differential fix and lag status. Example: $PXYA,713,488150.00,-1634756.995,-3664965.028,4942151.391,2.335,3.464, 4.156,0,2,0.4*08[CR][LF] 166 MiLLennium Command Descriptions Manual D Logs summary PXYB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 Message ID = 26 Message byte count = 88 Data Sync Checksum Message ID Message byte count Week number Seconds of week x y z StdDev of x StdDev of y StdDev of z Solution status Fix status Differential lag, age of differential corrections Bytes ➀ ➀ 3 1 4 4 4 8 8 8 8 8 8 8 4 4 8 Format char char integer integer integer double double double double double double double integer integer double Units weeks seconds metres metres metres metres metres metres seconds Offset 0 3 4 8 12 16 24 32 40 48 56 64 72 76 80 ➀ This log provides differential fix and lag status. MiLLennium Command Descriptions Manual 167 D Logs summary Figure D-2 The WGS84 ECEF Coordinate System 168 MiLLennium Command Descriptions Manual D Logs summary RALA/B Raw Almanac Almanac and health data are contained in subframes four and five of the satellite broadcast message. Subframe four contains information for SVs 25-32, as well as ionospheric, UTC and SV configuration data. Subframe five contains information for SVS 1-24. Subframes four and five each contain 25 pages of data, and each page contains ten 30-bit words of information as transmitted from the satellite. The RALA/B log outputs this information with parity bits checked and removed (ten words - 24 bits each). The log will not be generated unless all ten words pass parity. This log will alternately report each page from subframes four and five as they are collected. Logging this log onnew would be the optimal logging rate to capture data from pages in subframes four and five as they are received. RALA or 5). logs contain a hex representation of the raw almanac data (one of the possible 25 pages of either subframe 4 RALB contains the raw binary information. RALA Structure: $RALA chan # prn Field # Field type 1 2 3 4 $RALA chan # prn subframe 5 6 *xx [CR][LF] subframe *xx [CR][LF] Data Description Example Log header Channel number collecting almanac data (0-11) PRN of satellite from which data originated Subframe 4 or 5 of almanac data (60 hex characters) Checksum Sentence terminator $RALA 7 16 8B0A54852C964C661F086366FDBE00A 10D53DA6565F2503DD7C2AACBFED3 *05 [CR][LF] Example: $RALA,7,16,8B0A54852C964C661F086366FDBE00A10D53DA6565F2503DD7C2AACBFED3 *05[CR][LF] RALB Format: Field # 1 (header) 2 3 4 5 Message ID = 15 Data Sync Checksum Message ID Message byte count Channel number, 0-11 PRN number, 1-32 Almanac data, data [30] Filler bytes Message byte count = 52 Bytes 3 1 4 4 4 4 30 2 MiLLennium Command Descriptions Manual Format char char integer integer integer integer char char Units Offset 0 3 4 8 12 16 20 50 169 D Logs summary RASA/B Raw Almanac Set This is a single log for the entire Almanac data set. Only a complete log will be set so you do not have to worry about ephemeris data imitating an Almanac. RASA Structure: $RASA RxWeek RxSec subframe# page # subframe page # subframe AlmWeek Toa RxPrn # subframes : subframe# *xx Field # [CR][LF] Field type Data Description 1 2 3 4 5 6 7 8 9 10 $RASA RxWeek RxSec AlmWeek Toa RxPrn # subframes subframe # page # subframe Log header GPS week data received Approximate GPS seconds into week data received Almanac reference week Almanac reference seconds PRN of satellite from which data originated Number of subframes to follow Subframe Number Page Number Subframe of almanac data (60 hex characters, variable length up to 50 lines of subframe data ≅ 3300 bytes) ... ... ... variable variable ... ... ... *xx [CR][LF] Next subframe #, page # and subframe ... ... Last subframe #, page # and subframe Checksum Sentence terminator Example $RASA 926 246000 926 319488 1 30 4 2 8B0E784FDA315936EC4EF CAEFD3600A10C5C896ECE 9412862BD1AEFF0006 *32 [CR][LF] Example: $RASA,926,246000,926,319488,1,30,4,2,8B0E784FDA315936EC4EFCAEFD3600A10C5C896ECE9412862BD1AEFF 0006,4,3,8B0E784FDCB05A51184E0A26FD4C00A10DB2609586F2BE804B917BFCFFFB,4,4,8B0E784FDF315B65654 EFF68FD3A00A10CF78A21497D29E4D4504D000013,4,7,8B0E784FE6B15D2D014E07D2FD4800A10ADF5F8CDBAF9F5 720A25C22FF95,4,8,8B0E784FE9315E28E84E057AFD4600A10D1EB58EE4421223816DB8FFFFF7,4,9,8B0E784FEB B35F3D354E0BD6FD3C00A10D55E000EB1D3D371F95C8000001,4,17,8B0E784FFFB0773246204E524B414D4F444C3 54E204E38342F5A563822A8,4,18,8B0E78500232780C00FF002C00FD00000000000000034E9E0C90020CAAA9,4,2 5,8B0E785013B27F9999999099009999999099999990999080000FC0000FE8,5,1,8B0E784FD835411ED34E0835FD 4900A10C1A615B4ABE261433AAC3040001,5,2,8B0E784FDAB7428CFE4EFECDFD4000A10CF6B3DFACA157B083EBA2 CAFFE4,5,3,8B0E784FDD354314234E060EFD3600A10CD5DFDCCC69CB36EB45F407003C,5,4,8B0E784FDFB744236 74E15B4FD4800A10C850BB1F6DB53D7E65BA6060034,5,5,8B0E784FE2344509CB4E00A7FD3F00A10BEFB48EACD93 58704D58E0F000A,5,6,8B0E784FE4B54637BD4E0AB8FD3B00A10CF5E1492D95D0B001BEF6000000,5,7,8B0E784F E734474DE04E0C34FD3F00A10C57DFEF88A2B87952974463000A,5,9,8B0E784FEC344936594E0150FD3C00A10C5D 8AC38E0990CA01A8D3FE0004,5,10,8B0E784FEEB64A127F4E0E0BFD5100A10C72359FC2F5A04887F78A01001B,5, 13,8B0E784FF6374D0F544E0AA8FD4CFFA10EF2604E7FB038A9C9152201FFDB,5,14,8B0E784FF8B44E0C634E119F FD5800A10DBD37674077E0355E13D7030002,5,15,8B0E784FFB354F39E64E1902FD4D00A10D6F0D3E5342A05AC4A F843E0030,5,16,8B0E784FFDB45012294E0F48FD5400A10CA537A8C902C525BD198A040006,5,17,8B0E78500036 514FC34E19C3FD5100A10CCC0EC06367883FFB1622EA0018,5,18,8B0E785002B45238A44E0107FD3E00A10C455F0 43F43BCBA529078000018,5,19,8B0E78500536531AF54EF68FFD2D00A10D2D88F669888C38E202CA2100BD,5,21, 8B0E78500A355570FE4E0D99FD5200A10D0835E0458927E898247B0B0028,5,22,8B0E78500CB45653134EFEC6FD3 D00A10C1AB4776508EC2C7C0DFB02003D,5,23,8B0E78500F355763534E0FAAFD5400A10CF8376A23AA2FFC8D65B2 000017,5,24,8B0E785011B6583FB74E1C1EFD5200A10D8D0BCB65B2EAD8F641D8650050,5,25,8B0E78501435734 E9E00000000003F000FFFFC000000003F000000AAAAAB*39 170 MiLLennium Command Descriptions Manual D Logs summary RASB Format: Field # 1 2 3 4 5 6 7 8 9 10 11 12 13... Message ID = 66 Message byte count = 40 + (n * 32) Data Bytes Sync Checksum Message ID Message byte count Week data received Approximate seconds into week data received Almanac reference week Almanac reference seconds PRN of satellite from which data originated Number of subframes to follow Subframe number Page number Next PRN offset = 40 + (obs *32) Note: Variable Length = 40 + (n * 32). 3 1 4 4 4 8 4 4 4 4 1 1 Format char char integer integer integer double integer integer integer integer char char Maximum = 40 + (50 * 32) = 1640. MiLLennium Command Descriptions Manual Units weeks seconds weeks seconds Offset 0 3 4 8 12 16 24 28 32 36 40 41 Typical size (31 subframes) = 1032 bytes. 171 D Logs summary RBTA/B Satellite Broadcast Data: Raw Bits This message contains the satellite broadcast data in raw bits before FEC (forward error correction) decoding or any other processing. An individual message is sent for each PRN being tracked. For a given satellite, the message number increments by one each time a new message is generated. This data matches the SBTA/B data if the message numbers are equal. The data must be logged with the 'onnew' trigger activated to prevent loss of data. RBTA Structure: $RBTA week raw bits Field # seconds *xx prn cstatus message # # of bits [CR][LF] Field type Data Description Example 1 $RBTA Log header $RBTA 2 week GPS week number 883 3 seconds GPS seconds into the week 413908.000 4 prn PRN of satellite from which data originated 115 5 cstatus Channel Tracking Status 80812F14 6 message # Message sequence number 119300 7 # of bits Number of bits transmitted in the message. At present, aalways equals 256 bits. 256 8 raw bits 256 bits compressed into a 32 bytes. Hence, 64 hex characters are output. 30FB30FB30FB30F878DA621 94000F18322931B9EBDBC1C BC9324B68FBDAEBE8A 9 *xx Checksum *42 10 [CR][LF] Sentence terminator [CR][LF] RBTB Format: Message ID = 52 Field # Data Message byte count = 72 Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer 4 Message byte count 4 integer bytes 8 2 Week number 4 integer weeks 12 3 Seconds of week 8 double seconds 16 4 PRN number 4 integer 1-999 24 5 Channel Status 4 integer n/a 28 6 Message # 4 integer n/a 32 7 # of Bits 4 integer n/a 36 8 Raw Bits 32 char n/a 40 172 MiLLennium Command Descriptions Manual D Logs summary RCCA Receiver Configuration This log outputs a list of all current GPSCard command settings. Observing this log is a good way to monitor the GPSCard configuration settings. See Chapter 2 for the RCCA default list. RCCA Example: $RCCA,COM1,9600,N,8,1,N,OFF,ON*2B $RCCA,COM2,9600,N,8,1,N,OFF,ON*28 $RCCA,COM1_DTR,HIGH*70 $RCCA,COM2_DTR,HIGH*73 $RCCA,COM1_RTS,HIGH*67 $RCCA,COM2_RTS,HIGH*64 $RCCA,UNDULATION,TABLE*56 $RCCA,DATUM,WGS84*15 $RCCA,USERDATUM,6378137.000,298.257223563,0.000,0.000,0.000,0.000,0.000,0.000,0.000*6A $RCCA,SETNAV,DISABLE*5C $RCCA,MAGVAR,0.000*33 $RCCA,DYNAMICS,HIGH,AIR*6D $RCCA,UNASSIGNALL*64 $RCCA,ACCEPT,COM1,COMMANDS*5B $RCCA,ACCEPT,COM2,COMMANDS*58 $RCCA,UNLOCKOUTALL*20 $RCCA,RESETHEALTHALL*37 $RCCA,UNFIX*73 $RCCA,ANTENNAPOWER,ON*1E $RCCA,SETDGPSID,ALL*1D $RCCA,RTCMRULE,6CR*32 $RCCA,RTCM16T,*48 $RCCA,CSMOOTH,20.00*7E $RCCA,ECUTOFF,0.00*45 $RCCA,FREQUENCY_OUT,DISABLE*12 $RCCA,EXTERNALCLOCK,DISABLE*12 $RCCA,CLOCKADJUST,ENABLE*47 $RCCA,SETTIMESYNC,DISABLE*17 $RCCA,SETL1OFFSET,0.000000*3F $RCCA,MESSAGES,ALL,ON*67 $RCCA,SETCHAN,12*56 $RCCA,DGPSTIMEOUT,60.00,120.00*51 $RCCA,SAVEALMA,ONNEW*4E $RCCA,POSAVE,DISABLE*59 $RCCA,CONFIG,STANDARD*02 $RCCA,DIFF_PROTOCOL,DISABLED*47 $RCCA,LOG,COM2,RCCA,ONTIME,600.00*17 $RCCA,LOG,COM2,SATB,ONTIME,5.00*03 $RCCA,LOG,COM2,DOPB,ONCHANGED*7E $RCCA,LOG,COM2,MKPB,ONNEW*6D $RCCA,LOG,COM2,POSB,ONTIME,1.00*0D MiLLennium Command Descriptions Manual 173 D Logs summary RCSA/B Receiver Status The RCSA log will always output four records: one for VERSION, one for receiver CHANNELS, one for receiver CPU IDLE time, and one indicating receiver self-test STATUS. However, RCSB will embed the same information in a single record. Together, the RVSA/B and VERA/B logs supersede the RCSA/B logs. In other word this log is soon to be obsolete and eventually will be no longer supported. It is recommended then that you use the RVSA/B and VERA/B logs. RCSA Structure: $RCSA VERSION sw ver *xx [CR][LF] $RCSA CHANNELS # chans *xx [CR][LF] $RCSA IDLE idle time *xx [CR][LF] $RCSA STATUS rec status *xx [CR][LF] Log Data Identifier $RCSA VERSION $RCSA $RCSA CHANNELS IDLE $RCSA STATUS Data Description sw ver: Software information indicating model, S/N, S/W version and S/W version date # chans: Indicates number of parallel channels on GPSCard idle time: An integer number representing percent idle time for the CPU, with a valid range of 0 to 99 rec status: Indicates result of hardware self-test and software status as shown in Table D-5 Checksum String End *xx [CR][LF] *xx *xx [CR][LF] [CR][LF] *xx [CR][LF] Example: $RCSA,VERSION,GPSCard-2 3951R LGR94160001 HW 16 SW 3.15 Mar 31/94*16 $RCSA,CHANNELS,10*12 $RCSA,IDLE,40*03 $RCSA,STATUS,000007F6*60 The status code is a hexadecimal number representing the results of the GPSCard BIST test and software status. As an example, the status code '000000F6' indicates that the GPSAntenna is not working properly or is disconnected and the GPSCard is good, while '000000F7' indicates that the GPSAntenna and the GPSCard are both functioning properly. See Table D-5 for a detailed description of the status code. Bit 0 is the least significant bit of the status code and Bit 16 is the most significant bit. RCSB Format: Field # 1 (header) 2 3 4 5 6 NOTES: Message ID = 13 Message byte count = 100 Data Sync Checksum Message ID Message byte count Software version #, ASCII Number of receiver channels CPU idle time, percent Filler Self-test status Bytes 3 1 4 4 80 1 1 2 4 Format char char integer integer char char char bytes integer Offset 0 3 4 8 12 92 93 94 96 See Table D-5 for a detailed GPSCard Receiver Self-test Status Code table and bit descriptions. Self test bits 2, 3, 4, 6, 7 are set only once when the GPSCard is first powered up. All other bits are set by internal test processes each time the RCSA/B log is output . 174 MiLLennium Command Descriptions Manual D Logs summary REPA/B Raw Ephemeris REPA This log contains the raw Binary information for subframes one, two and three from the satellite with the parity information removed. Each subframe is 240 bits long (10 words - 24 bits each) and the log contains a total 720 bits (90 bytes) of information (240 bits x 3 subframes). This information is preceded by the PRN number of the satellite from which it originated. This message will not be generated unless all 10 words from all 3 frames have passed parity. Ephemeris data whose toe (time of ephemeris) is older than six hours will not be shown. Structure: $REPA Field # prn subframe1 subframe2 Field type subframe3 *xx Data Description [CR][LF] Example 1 2 3 $REPA prn subframe1 Log header PRN of satellite from which data originated Subframe 1 of ephemeris data (60 hex characters) 4 subframe2 Subframe 2 of ephemeris data (60 hex characters) 5 subframe3 Subframe 3 of ephemeris data (60 hex characters) 6 7 *xx [CR][LF] Checksum Sentence terminator $REPA 14 8B09DC17B9079DD7007D5D E404A9B2D 04CF671C6036612560000021 804FD 8B09DC17B98A66FF713092F 12B359D FF7A0254088E1656A10BE2F F125655 8B09DC17B78F0027192056E AFFDF2724C 9FE159675A8B468FFA8D066 F743 *57 [CR][LF] Example: $REPA,14,8B09DC17B9079DD7007D5DE404A9B2D04CF671C6036612560000021804FD, 8B09DC17B98A66FF713092F12B359DFF7A0254088E1656A10BE2FF125655, 8B09DC17B78F0027192056EAFFDF2724C9FE159675A8B468FFA8D066F743*57[CR][LF] REPB Format: Field # 1 (header) 2 3-4-5 Message ID = 14 Data Sync Checksum Message ID Message byte count PRN number, 1-32 Ephemeris data, data [90] Filler bytes Message byte count = 108 Bytes 3 1 4 4 4 90 2 MiLLennium Command Descriptions Manual Format char char integer integer integer char char Offset 0 3 4 8 12 16 106 175 D Logs summary RGEA/B/D Channel Range Measurements RGEA/B/D contain the channel range measurements for the currently observed satellites. The RGED message is a compressed form of the RGEB message. When using these logs, please keep in mind the constraints noted along with the description. It is important to ensure that the receiver clock has been set and can be monitored by the bits in the rec-status field. Large jumps in range as well as ADR will occur as the clock is being adjusted. If the ADR measurement is being used in precise phase processing it is important not to use the ADR if the "parity known" flag in the ch-tr-status field is not set as there may exist a half (1/2) cycle ambiguity on the measurement. The tracking error estimate of the pseudorange and carrier phase (ADR) is the thermal noise of the receiver tracking loops only. It does not account for possible multipath errors or atmospheric delays. RGEA and RGEB contain all of the new extended channel tracking status bits (see Table D-7), while RGED contains only the lowest 24 bits. The receiver self-test status word (see Table D-5, following the RGEA/B/D log tables) now also indicates L2, OCXO and new almanac status. If both the L1 and L2 signals are being tracked for a given PRN, two entries with the same PRN will appear in the range logs. As shown in Table D-7 (Channel Tracking Status), these entries can be differentiated by bit 19, which is set if there are multiple observables for a given PRN, and bit 20, which denotes whether the observation is for L1 or L2. This is to aid in parsing the data. 176 MiLLennium Command Descriptions Manual D Logs summary RGEA Structure: $RGEA prn week seconds # obs rec status psr psr std adr adr std dopp C/No locktime ch-tr-status psr psr std adr adr std dopp C/No locktime ch-tr-status : prn *xx Field # [CR][LF] Field type Data Description Example 1 2 3 4 5 6 7 $RGEA week seconds # obs rec status prn psr Log header GPS week number GPS seconds into the week Number of satellite observations with information to follow Receiver self-test status (see Table D-5, following) Satellite PRN number (1-32) of range measurement Pseudorange measurement (m) $RGEA 845 511089.00 14 000B20FF 4 23907330.296 8 psr std Pseudorange measurement standard deviation (m) 0.119 9 adr Carrier phase, in cycles (accumulated Doppler range) -125633783.992 10 11 12 adr std dopp C/N0 Estimated carrier phase standard deviation (cycles) Instantaneous carrier Doppler frequency (Hz) Signal to noise density ratio C/N0 = 10[log10(S/N0)] (dB-Hz) 0.010 3714.037 44.8 13 14 locktime ch-tr-status 1928.850 82E04 ... ... ... variable variable ... ... ... *xx [CR][LF] Number of seconds of continuous tracking (no cycle slipping) Hexadecimal number indicating phase lock, channel number and channel tracking state, as shown in Table D-7. Next PRN #, psr, psr std, adr, adr std, dopp, C/No, locktime,ch-tr-status ... Last PRN #, psr, psr std, adr, adr std, dopp, C/No, locktime, ch-tr-status Checksum Sentence terminator *30 [CR][LF] Example (carriage returns have been added between observations for clarity): $RGEA,845,511089.00,14,000B20FF 4,23907330.296,0.119,-125633783.992,0.010,3714.037,44.8,1928.850,82E04, 4,23907329.623,1.648,-97896180.284,0.013,2894.285,35.0,1746.760,582E0B, 2,21298444.942,0.040,-111954153.747,0.006,-1734.838,54.2,17466.670,82E14, 2,21298444.466,0.637,-87236867.557,0.006,-1351.607,43.3,17557.260,582E1B, 9,22048754.383,0.063,-115874135.450,0.006,2174.006,50.4,5489.100,82E24, 9,22048754.424,0.641,-90291443.071,0.006,1694.238,43.2,5489.100,582E2B, 15,23191384.847,0.261,-121887295.980,0.017,-2069.744,38.0,9924.740,82E34, 15,23191384.663,0.596,-94977002.452,0.010,-1612.587,43.8,9881.830,582E3B, 26,24063897.737,0.199,-126477739.189,0.014,-2654.682,40.3,12821.640,82E54, 26,24063898.913,1.043,-98553986.239,0.013,-2068.380,39.0,12793.280,582E5B, 7,20213352.139,0.037,-106237901.461,0.005,439.943,55.0,10313.040,82E74, 7,20213351.196,0.498,-82782498.454,0.007,343.020,45.4,9977.400,582E7B, 27,24393726.829,0.123,-128229016.323,0.012,-4047.338,44.5,22354.119,82E94, 27,24393728.057,1.805,-99918535.513,0.013,-3153.559,34.2,22301.830,582E9B *30 MiLLennium Command Descriptions Manual 177 D Logs summary RGEB Format: Message ID = 32 Field # 1 (header) Message byte count = 32 + (obs x 44) Data Bytes Format Units Offset 2 3 4 5 6 7 8 9 Sync Checksum Message ID Message byte count Week number Seconds of week Number of observations (obs) Receiver self-test status PRN Pseudorange StdDev pseudorange Carrier phase - accumulated Doppler range, cycles 3 1 4 4 4 8 4 4 4 8 4 8 char char integer integer integer double integer integer integer double float double 10 StdDev - accumulated Doppler range, cycles 4 float 11 12 Doppler frequency C/N0 4 4 float float Hz dB-Hz 60 64 13 14 15... Locktime Tracking status Next PRN offset = 32 + (obs x 44) 4 4 float integer seconds 68 72 178 weeks seconds metres metres 0 3 4 8 12 16 24 28 32 36 44 48 56 MiLLennium Command Descriptions Manual D Logs summary RGED Format: Message ID = 65 Field # Data 1 (header) Sync Checksum Message ID Message byte count Number of obs Week number Seconds of week Receiver status First PRN range record 2 3 4 5 6 Message byte count =24 + (20 x number of obs) Bytes 3 1 4 4 2 2 4 4 20 Format Scale char char integer integer integer integer See Table D-6, following the Detailed Bit Descriptions of the Self-Test 1 1 1/100 1 Offset 0 3 4 8 12 14 16 20 24 Next PRN offset = 24 + (20 x number of obs) MiLLennium Command Descriptions Manual 179 D Logs summary Table D-5 Receiver Self-Test Status Codes N7 N 6 27 26 25 N 5 24 23 22 21 N 4 20 N 3 19 18 17 16 15 14 13 12 11 N 2 10 9 N 1 8 7 6 5 N 0 4 3 2 1 0 <- <- Nibble Number B it Descriptio n lsb = 0 ANTENNA 1 L1 PLL Range Values Hex Value 1 =good, 0 =bad 00000001 1 =good, 0 =bad 00000002 2 RAM 1 =good, 0 =bad 00000004 3 ROM 1 =good, 0 =bad 00000008 4 DSP 1 =good, 0 =bad 00000010 5 L1 AGC 1 =good, 0 =bad 00000020 6 COM 1 1 =good, 0 =bad 00000040 7 COM 2 1 =good, 0 =bad 00000080 8 WEEK 1 =not set , 0 =set 00000100 9 NO COARSETIME 1 =not set , 0 =set 00000200 10 NO FINETIME 1 =not set , 0 =set 00000400 11 L1 JAMMER 1 =present , 0 =normal 00000800 12 BUFFER COM 1 1 =overrun, 0 =normal 00001000 13 BUFFER COM 2 1 =overrun, 0 =normal 00002000 14 BUFFER CONSOLE 1 =overrun, 0 =normal 00004000 15 CPU OVERLOAD 1 =overload, 0 =normal 00008000 16 ALMANAC SAVED IN NVM 1 =yes, 0 =no 00010000 17 L2 AGC 1 =good, 0 =bad 00020000 18 L2 JAMMER 1 =present , 0 =normal 00040000 19 L2 PLL 1 =good, 0 =bad 00080000 20 OCXO PLL 1 =good, 0 =bad 00100000 21 SAVED ALMA. NEEDS UPDATE 1 =yes, 0 =no 00200000 22 ALMANAC INVALID 1 =invalid, 0 =valid 00400000 23 POSITION SOLUTION INVALID 1 =invalid, 0 =valid 00800000 24 POSITION FIXED 1 =yes, 0 =no 01000000 25 CLOCK MODEL INVALID 1 =invalid, 0 =valid 02000000 26 CLOCK STEERING DISABLED 1 =disabled, 0 =enabled 04000000 27 RESERVED 28-31 RESERVED Notes on Table D-5: 1. Bit 3: On OEM GPSCards, “ROM” includes all forms of non-volatile memory. 2. Bits 12-15: Flag is reset to 0 five minutes after the last overrun/overload condition has occurred. GPSCard example: All OK = 0000 0000 0000 1010 0000 0000 1111 1111 (binary) = 000A00FF (hexadecimal) ; using a VCTCXO oscillator. RECEIVER STATUS - DETAILED BIT DESCRIPTIONS OF SELF-TEST Bit 0 Antenna 1 This bit will be set good if the antenna is drawing the appropriate amount of current from the GPSCard antenna jack. 0 If the antenna connections are shorted together then this bit will be clear (0) indicating a possible antenna port problem. Bit 1 L1 PLL 1 When the L1 RF downconverter passes self-test, the bit will be set to 1. 0 If a fault is detected in the L1 RF downconverter, this bit is set to 0. Bit 2 RAM 1 When this bit is set to 1, the receiver RAM has passed the self-test requirements. 0 If the bit has been set to 0, then RAM test has failed; please contact NovAtel Customer Service. Bit 3 ROM (Note: “ROM” includes all forms of nov-volatile memory (NVM)) 1 When this bit is set to 1, the receiver ROM test has passed the self test requirements. 0 A zero bit indicates the receiver has failed the ROM test. Bit 4 DSP 180 MiLLennium Command Descriptions Manual D Logs summary 1 This bit will be set to 1 when the digital signal processors (DSP) have passed the self-test requirements. 0 If this bit is set to 0, one or both of the Service. Bit 5 L1 AGC 1 When set to 1, the L1AGC circuits are operating within normal range of control. 0 This bit will be set clear if the L1AGC is operating out of normal range. Failure of this test could be the result of various possibilities, such as: bad antenna LNA, excessive loss in the antenna cable, faulty RF downconverter, or a pulsating or high power jamming signal causing interference. If this bit is continuously set clear, and you cannot identify an external cause for the failed test, please contact NovAtel Customer Service. DSP chips has failed self-test; please contact NovAtel Customer Bit 6 COM1 1 When set to 1, the COM1 UART has passed the self-test requirements. 0 If set to 0, the COM1 UART has failed self-test and cannot be used for reliable communications. Bit 7 COM2 1 When set to 1, the COM2 UART has passed the self-test requirements. 0 If set to 0, the COM2 UART has failed self-test and cannot be used for reliable communications. Bits 8, 9, 10 Week / No Coarsetime / No Finetime 0 These bits indicate the state of the receiver time and are set only once, generally in the first few minutes of operation, in the presence of adequate numbers of satellite signals to compute position and time. 1 If these bits are not all set to zero, then the observation data, pseudorange measurement, carrier phase, and Doppler measurements may jump as the clock adjusts itself. Bit 11 L1 Jammer Detection 0 Normal operation is indicated when this bit is 0. 1 If set to 1, the receiver has detected a high power signal causing interference. When this happens, the receiver goes into a special anti-jamming mode where it re-maps the A/D decode values as well as special L1AGC feedback control. These adjustments help to minimize the loss that will occur in the presence of a jamming signal. You should monitor this bit, and if set to 1, do your best to remedy the cause of the jamming signal. Nearby transmitters or other electronic equipment could be the cause of interference; you may find it necessary to relocate your antenna position if the problem persists. Bits 12, 13, 14 Buffer COM 1 / COM 2 0 Normal operation is indicated by a 0 value. 1 These bits are set to 1 to inform the user when any of the 8-Kbyte output buffers have reached an overrun condition (COM1 or COM2). Over-run is caused by requesting more log data than can be taken off the GPSCard because of bit rate limitations or slow communications equipment. If this happens, the new data attempting to be loaded into the buffer will be discarded. The receiver will not load a partial data record into an output buffer. The flag resets to 0 five minutes after the last overrun occurred. Bit 15 CPU Overload 0 Normal operation is indicated by a 0 value. 1 A value of 1 indicates that the CPU is being over-taxed. This may be caused by requesting an excessive amount of information from the GPSCard. If this condition is occurring, limit redundant data logging or change to using binary data output formats, or both. You should attempt to tune the logging requirements to keep the idle time above 20% for best operation. If the average idle % drops below 10% for prolonged periods of time (2-5 seconds), critical errors may result in internal data loss and the over-load bit will be set to 1. You can monitor the CPU % idle time by using the RvSA log message. The flag resets to 0 five minutes after the first overload occurred. Note: As the amount of CPU power becomes limited, the software will begin to slow down the position calculation rate. If the CPU becomes further limited, the software will begin to skip range measurement processing. Priority processing goes to the tracking loops. MiLLennium Command Descriptions Manual 181 D Logs summary Bit 16 Almanac Saved 0 Almanac not saved in non-volatile memory. 1 Almanac saved in non-volatile memory (12 channel OEM cards only). Bit 17 L2AGC 1 When set to 1, the L2ARG circuits are operating within normal range of control. 0 This bit will be set clear if the L2AGC is operating out of normal range. Failure of this test could be the result of various possibilities, such as: bad antenna LNA, excessive loss in the antenna cable, faulty RF downconverter, or a pulsating or high power jamming signal causing interference. If this bit is continuously set clear, and you cannot identify an external cause for the failed test, please contact NovAtel Customer Service. Bit 18 L2Jammer Detection 0 Normal operation is indicated when this bit is 0. 1 If set to 1, the receiver has detected a high power signal causing interference. When this happens, the receiver goes into a special anti-jamming mode where it re-maps the A/D decode values as well as special L2AGC feedback control. These adjustments help to minimize the loss that will occur in the presence of a jamming signal. You should monitor this bit, and if set to 1, do your best to remedy the cause of the jamming signal. Nearby transmitters or other electronic equipment could be the cause of interference; you may find it necessary to relocate your antenna position if the problem persists. Bit 19 L2PLL 1 When the L2 RF downconverter passes self-test, the bit will be set to 1. 0 If a fault is detected in the L2 RF downconverter, this bit is set to 0. Bit 20 OCXOPLL 1 When the OCXOPLL bit passes self-test, the bit will be set to 1. 0 If a fault is detected in the OCXOPLL bit, this bit is set to 0. Bit 21 Saved Almanac Needs Update 1 When the almanac received is newer than the one currently stored in NVM (non-volatile memory), the bit will be set to 1. 0 This bit will be set to 0 if an almanac has not been received that is newer than the one stored in memory. Bit 22 Almanac Invalid 1 No almanac in use 0 Valid almanac in use Bit 23 Position Solution Invalid 1 Position solution is not valid 0 Valid position computed Bit 24 Position Fixed 1 A fix position command has been accepted 0 Position has not been fixed Bit 25 Clock Model Invalid 1 Clock model has not stabilized 0 Clock model is valid Bit 26 Clock Steering Disabled 1 Clockadjust disable command has been accepted 0 Clockadjust is enabled 182 MiLLennium Command Descriptions Manual D Logs summary Table D-6 Range Record Format (RGED only) Data PRN ① C/No ② Lock time ③ ADR ④ Doppler frequency Pseudorange StdDev - ADR StdDev - pseudorange Channel Tracking status ➅ Bit(s) from first to last Length (bits) 0..5 6..10 11.31 32..63 68..95 64..67 msn; 96..127 lsw 128..131 132..135 136..159 6 5 21 32 28 36 4 4 24 Format integer integer integer integer 2's comp. integer 2's comp. integer 2's comp. integer integer Scale Factor 1 (20+n) dB-Hz 1/32 s 1/256 cycles 1/256 Hz 1/128 m (n+1) / 512 cyc see ➄ see Table D-7 Notes on Table D-6: ① Only PRNs 1 - 63 are reported correctly (Note: while there are only 32 PRNs in the basic GPS scheme, situations exist which require the use of additional PRNs) ② C/No is constrained to a value between 20 - 51 dB-Hz. Thus, if it is reported that C/No = 20 dB-Hz, the actual value could be less. Likewise, if it is reported that C/No = 51 dB-Hz, the true value could be greater. ③ Lock time rolls over after 2,097,151 seconds. ④ ADR (Accumulated Doppler Range) is calculated as follows: ADR_ROLLS = [( -RGED_PSR / WAVELENGTH - RGED_ADR)] / MAX_VALUE IF (ADR_ROLLS ≤ -0.5) ADR_ROLLS = ADR_ROLLS - 0.5 ELSE ADR_ROLLS = ADR_ROLLS + 0.5 (At this point integerise ADR_ROLLS) CORRECTED_ADR = RGED_ADR + (MAX_VALUE * ADR_ROLLS) where: ADR has units of cycles WAVELENGTH = 0.1902936727984 for L1 WAVELENGTH = 0.2442102134246 for L2 MAX_VALUE = 8388608 ➄ Code RGED 0 0.000 to 0.050 1 0.051 to 0.075 2 0.076 to 0.113 3 0.114 to 0.169 4 0.170 to 0.253 5 0.254 to 0.380 6 0.381 to 0.570 7 0.571 to 0.854 8 0.855 to 1.281 9 1.282 to 2.375 10 2.376 to 4.750 11 4.751 to 9.500 12 9.501 to 19.000 13 19.001 to 38.000 14 38.001 to 76.000 15 76.001 to 152.000 ➅ Only bits 0 - 23 are represented in the RGED log MiLLennium Command Descriptions Manual 183 D Logs summary Table D-7 Channel Tracking Status N 7 31 30 29 N 6 28 27 26 25 N 5 24 23 22 21 N 4 20 19 18 17 N 3 16 15 14 13 N 2 12 11 10 9 N 1 8 7 6 5 N 0 4 3 2 1 0 <- <- Nibble Number Bit Description Range Values lsb =0 Hex. 1 1 Tracking st at e 0 - 11 See below 2 2 4 3 8 4 10 5 0 - n (0 =f irst , n =last ) 20 6 Channel number (n depends on GPSCard) model) 40 1 =Lock, 0 =Not locked 200 7 8 80 100 9 Phase lock f lag 10 Parit y known f lag 1 =Known, 0 =Not known 400 11 Code locked f lag 1 =Lock, 0 =Not locked 800 0 - 7 See below 2000 12 1000 13 Correlat or spacing 14 4000 15 0=GPS 3=Pseudolit e GPS 8000 16 Sat ellit e syst em 1=GLONASS 4-7 Reserved 10000 17 2=WAAS 18 Reserved 20000 40000 19 Grouping 1 =Grouped, 0 =Not grouped 80000 20 Frequency 1 =L2, 0 =L1 100000 21 Code t ype 0 =C/ A 2 =P-codeless 200000 22 1 =P 3 =Reserved Foreword error 23 Forward errorcorrection correct i 1 =FEC enabled, 0 =no FEC 400000 800000 24 : Reserved 29 30 Ext ernal range 1 =Ext . range, 0 =Int . range 31 Channel assignment 1 =Forced, 0 =Aut omat ic Table D-7 is referenced by the ETSA/B, and RGEA/B/D logs. Table D-7, Bits 0 - 3 : Channel Tracking State State 0 1 2 3 4 5 Description L1 Idle L1 Sky search L1 Wide frequency band pull-in L1 Narrow frequency band pull-in L1 Phase-lock loop L1 Re-acquisition State 6 7 8 9 10 11 Description L1 Steering L1 Frequency-lock loop L2 Idle L2 P-code alignment L2 Search L2 Phase-lock loop Higher numbers are reserved for future use Table D-7, Bits 12-14 : Correlator Spacing State 0 1 2 Description Unknown: this only appears in versions of software previous to x.4x, which didn’t use this field Standard correlator: spacing = 1 chip Narrow Correlator: spacing < 1 chip Higher numbers are reserved for future use 184 MiLLennium Command Descriptions Manual D Logs summary RINEX The Receiver-Independent Exchange (RINEX) format is a broadly-accepted, receiver-independent format for storing GPS data. It features a non-proprietary ASCII file format that can be used to combine or process data generated by receivers made by different manufacturers. RINEX was originally developed at the Astronomical Institute of the University of Berne. Version 2, containing the latest major changes, appeared in 1990; subsequently, minor refinements were added in 1993. To date, there are three different RINEX file types observation files, broadcast navigation message files and meteorological data files. Please see Chapter 7, Rinex Standard Commands and Logs for further details. MiLLennium Command Descriptions Manual 185 D Logs summary RPSA/B Reference Station Position and Health This log contains the ECEF XYZ position of the reference station as received through the RTCA Type 7 or RTCM Type 3 message. It also features a time tag, the health status of the reference station, and the station ID. This information is set at the reference station using the FIX POSITION command. RPSA Structure: $RPSA week Field # seconds X Field type 1 2 3 4 5 6 7 8 $RPSA week seconds X Y Z health stn ID 9 10 *xx [CR][LF] Y Z health stn ID [CR][LF] *xx Data Description Example Log header GPS week number GPS time into the week (seconds) ECEF X value (metres) ECEF y value (metres) ECEF z value (metres) Reference Station Health Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Checksum Sentence terminator $RPSA 872 174962.00 -1634962.8660 -3664682.4140 4942301.3110 0 119 *32 [CR][LF] Example: $RPSA,872,174962.00,-1634962.8660,-3664682.4140,4942301.3110,0,119*32[CR][LF] RPSB Format: Field # 1 (header) 2 3 4 5 6 7 8 186 Message ID = 60 Message byte count = 56 Data Sync Checksum Message ID Message byte count GPS week number GPS time into the week ECEF X value ECEF Y value ECEF Z value Reference station health Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Bytes 3 1 4 4 4 8 8 8 8 4 4 Format char char integer integer integer double double double double integer integer Units weeks seconds metres metres metres Offset 0 3 4 8 12 16 24 32 40 48 52 MiLLennium Command Descriptions Manual D Logs summary RTCA Standard Logs The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential Global Navigation Satellite System (DGNSS) Special Category I (SCAT-I) precision instrument approaches. The RTCA Standard is in a preliminary state. NovAtel’s current support for this Standard is based on "Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I (SCAT-I)" dated August 27, 1993 (RTCA/DO-217). See Chapter 6, Message Formats, 6.1 RTCA Standard Logs for more detailed information on RTCA standard logs. RTCM Standard Logs The Radio Technical Commission for Maritime Services (RTCM) was established to facilitate the establishment of various radio navigation standards, which includes recommended GPS differential standard formats. The standards recommended by the Radio Technical Commission for Maritime Services Special Committee 104, Differential GPS Service (RTCM SC-104,Washington, D.C.), have been adopted by NovAtel for implementation into the GPSCard. Because the GPSCard is capable of utilizing RTCM formats, it can easily be integrated into positioning systems around the globe. See Chapter 6, Message Formats, 6.2 RTCM Standard Commands and Logs for more detailed information on standard logs. RTCM MiLLennium Command Descriptions Manual 187 D Logs summary RTKA/B Computed Position - Time Matched RTK This log represents positions that have been computed from time matched reference and remote observations. There is no reference station extrapolation error on these positions but because they are based on buffered measurements, they lag real time by some amount depending on the latency of the data link. If the remote receiver has not been enabled to accept RTK differential data, or is not actually receiving data leading to a valid solution, this will be reflected by the code shown in field #16 (RTK ststus) and #17 (position type). The data in the logs will change only when a reference observation (RTCM Type 59 or the corresponding RTCA Type 7) changes. If the log is being output at a fixed rate and the differential data is interrupted, then the RTKA/B logs will continue to be output at the same rate but the position and time will not change. A good message trigger for this log is "ONCHANGED". Then, only positions related to unique reference station messages will be produced, and the existence of this log will indicate a successful link to the reference station. RTKA Structure: $RTKA week lon lat lat σ lon σ posn type Field # seconds hgt hgt σ dyn mode Field type #sv #high undulation datum ID soln status stn ID L1L2 #high *xx rtk status [CR][LF] Data Description Example 1 2 3 4 5 $RTKA week seconds #sv #high 6 7 L1L2 #high lat 8 lon 9 10 hgt undulation 11 12 datum ID lat σ Log header GPS week number GPS time into the week (in seconds) Number of matched satellites; may differ from the number in view. Number of matched satellites above RTK mask angle; observations from satellites below mask are heavily de-weighted Number of matched satellites above RTK mask angle with both L1 and L2 available Latitude of position in current datum, in decimal fraction format. A negative sign implies South latitude Longitude of position in current datum, in decimal fraction format. A negative sign implies West longitude Height of position in current datum, in metres above mean sea level Geoidal separation, in metres, where positive is above ellipsoid and negative is below ellipsoid Current datum (see Appendix G) Standard deviation of latitude solution element, in metres $RTKA 872 174962.00 8 7 13 lon σ Standard deviation of longitude solution element, in metres 0.0039 14 hgt σ Standard deviation of height solution element, in metres 0.0066 15 16 17 18 19 20 21 soln status rtk status posn type dyn mode stn ID *xx [CR][LF] Solution status (seeTable D-1) RTK status (see Tables D-3, D-4 ) Position type (see Table D-2) Dynamics mode (0= static, 1= kinematic) Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385) Checksum Sentence terminator 0 0 4 0 119 *33 [CR][LF] 7 51.11358039754 -114.04358003164 1059.4105 -16.2617 61 0.0036 Example: $RTKA,872,174962.00,8,7,7,51.11358039754,-114.04358003164,1059.4105, -16.2617,61,0.0036,0.0039,0.0066,0,0,4,0,119*33[CR][LF] 188 MiLLennium Command Descriptions Manual D Logs summary RTKB Format: Message ID = 61 Message byte count = 116 Field # Data 1 (header) Sync Checksum Message ID Message byte count Week number GPS time into the week Number of matched satellites (00-12) Number of matched satellites above RTK mask angle Number of matched satellites above RTK mask angle with both L1 and L2 available Latitude Longitude Height above mean sea level Undulation Datum ID Standard deviation of latitude Standard deviation of longitude Standard deviation of height Solution status RTK status Position type Dynamics mode Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 15179385) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 MiLLennium Command Descriptions Manual Bytes Format 3 1 4 4 4 8 4 4 4 char char integer integer integer double integer integer integer 8 8 8 8 4 8 8 8 4 4 4 4 4 double double double double integer double double double integer integer integer integer integer Units weeks seconds degrees degrees metres metres metres metres metres Offset 0 3 4 8 12 16 24 28 32 36 44 52 60 68 72 80 88 96 100 104 108 112 189 D Logs summary RTKOA/B RTK Solution Parameters This is the “RTK output” log, and it contains miscellaneous information regarding the RTK solution. It is based on the matched update. Note that the length of the log messages will vary depending on the number of matched satellites in the solution, a quantity represented by #sv in the field numbers. RTKOA Structure: $RTKOA week sec status #sat #high L1L2 #high #sv σxy σxz σyx σyy σyz ∆y ∆z σ∆x σ∆y σ∆z dyn search combn σxx σzx σzy σzz ∆x rsrv rsrv ref id sat id amb res sat id amb res *xx [CR][LF] #res : Field# Field type 1 2 3 4 5 6 $RTKOA week sec status #sat #high 7 L1L2 #high 8 #sv 9 10 11 12-20 dyn search combn [σ] Data Description Example Log header GPS week number GPS time into the week (in seconds) RTK status (see Table D-10) Total number of matched satellites available to both receivers Number of matched satellites above RTK mask angle; observations from satellites below mask are heavily deweighted Number of matched satellites above RTK mask angle with both L1 and L2 available Number of matched satellites in solution; may differ from the number in view. Dynamics mode (0=static, 1=kinematic) Searcher status (see Table D-9). Number of possible lane combinations remaining The σxx,σxy,σxz,σyx,σyy,σyz,σzx,σzy, and σzz components, in (meters)2, of the ECEF position covariance matrix (3 x 3) 21-23 24-26 ∆x,∆y,∆z σ∆x,σ∆y,σ∆z ECEF x.y,z of baseline from float solution in meters x,y,z standard deviations of float solution baseline in meters 27 28 29 30 31 32 33 ... ... ... variable variable rsrv rsrv ref id #res sat id amb res ... ... ... *xx [CR][LF] Reserved for future use Reserved for future use Reference PRN Number of residual sets to follow PRN number Ambiguity type (see Table D-8) Residual in metres Next PRN number, amb, res ... Last PRN number, amb, res Checksum Sentence terminator 190 $RTKOA 929 237639.00 1 8 8 8 8 0 4 1 0.000006136,0.000003797,-0.000003287, 0.000003797,0.000013211,-0.000007043, -0.000006287,-0.000007043,0.000018575 3.2209,-3.0537,-1.2024 0.0183,0.0138,0.0124 0 0.0000 1 7 21 6 -0.001199 *60 [CR][LF] MiLLennium Command Descriptions Manual D Logs summary Example: $RTKOA,929,237639.00,1,8,8,8,8,0,4,1,0.000006136,0.000003797, -0.000006287,0.000003797,0.000013211,-0.000007043,-0.000006287, -0.000007043,0.000018575,3.2209,-3.0537, -1.2024,0.0183,0.0138,0.0124,0,0.0000,1,7, 21,6,-0.001199,23,6,0.005461,31,6,0.009608,9,6,0.001963, 15,6,0.000208,29,6,-0.005643,25,6,-0.004366*60[CR][LF] RTKOB Format: Message ID = 62 Message byte count = 196 + (#res)*16 Field # 1 (header) Data Bytes Format Units Offset 3 1 4 4 4 8 4 4 char char integer integer integer double integer integer 4 integer 32 4 integer 36 4 4 4 4 integer integer integer integer 40 44 48 52 12-20 Sync Checksum Message ID Message byte count GPS week number GPS time into the week RTK status (see Table D-10) Total number of matched satellites available to both receivers. Number of matched satellites above RTK mask angle Number of matched satellites above RTK mask angle with both L1 and L2 available Number of matched satellites in solution Dynamics mode (0=static, 1=kinematic) Searcher status (see Table D-9). Number of possible lane combinations remaining Position covariance matrix 72 double 21-23 24-26 27 28 29 30 31 32 33 34 Baseline in ECEF x,y,z from float filter Standard deviations of x,y,z from float filter Reserved for future use Reserved for future use Reference PRN Number of residual sets to follow PRN number Ambiguity type (see Table D-8) Residual Next PRN offset = 196 + (#res)*16 24 24 4 8 4 4 4 4 8 double double integer double integer integer integer integer double 2 3 4 5 6 7 8 9 10 11 MiLLennium Command Descriptions Manual weeks s m2 m m 0 3 4 8 12 16 24 28 56 128 152 176 180 188 192 196 m 191 D Logs summary Table D-8 Ambiguity Types Ambiguity Type 0 1 2 3 4 5 6 7 8 9 10 Definition L1 only floating Wide lane fixed integer Reserved Narrow lane floating Iono–free floating Reserved Narrow lane fixed integer Iono–free fixed discrete L1 only fixed integer Reserved Undefined type Higher numbers are reserved for future use Table D-9 Searcher Status Searcher Status Definition 0 1 2 3 4 No search requested Searcher buffering measurements Currently searching Search decision made Hand-off to L1 and L2 complete Higher numbers are reserved for future use Table D-10 RTK Status RTK Status 1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 192 Definition Good narrowlane solution Good widelane solution Good L1/L2 converged float solution Good L1/L2 unconverged float solution Good L1 converged solution Good L1 unconverged solution Reserved for future use Insufficient observations Variance exceeds limit Residuals exceed limit Delta position too large Negative variance Undefined RTK initialize MiLLennium Command Descriptions Manual D Logs summary RVSA/B Receiver Status This log conveys various status parameters of the receiver system. If the system is a multiple-GPSCard unit with a master card, certain parameters are repeated for each individual GPSCard. If the system is composed of only one GPSCard, then only the parameters for that unit are listed. Together, the RVSA/B and VERA/B logs supersede the RCSA/B logs. Note that the number of satellite channels (the number of satellites the receiver is capable of tracking) is not necessarily the same as the number of signal channels. This is because one L1/L2 satellite channel requires two signal channels. Therefore the 12-channel MiLLennium GPSCard will report 24 signal channels in this field. This number represents the maximum number of channels reporting information in logs such as ETSA/B and RGEA/ B/D. RVSA Structure: $RVSA idle week seconds sat_chan sig_chan num reserve status : idle *xx status [CR][LF] Field # 1 2 3 4 5 6 7 8 9 ... ... ... variable variable Field type $RVSA week seconds sat_chan sig_chan num reserve idle status ... ... ... *xx [CR][LF] Data Description Log header GPS week number GPS seconds into the week. Number of satellite channels Number of signal channels Number of cards Reserved field First GPSCard: CPU idle time (percent) First GPSCard: Self-test status (see Table D-5) Next GPSCard: CPU idle time & self-test status ... Last GPSCard: CPU idle time & self-test status Checksum Sentence terminator Example $RVSA 847 318923.00 12 24 1 16.00 000B00FF *42 [CR][LF] Example: $RVSA,847,318923.00,12,24,1,,16.00,000B00FF*42[CR][LF] MiLLennium Command Descriptions Manual 193 D Logs summary RVSB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 8 & 9 are repeated for each card Message ID = 56 Data Message byte count =28+ (8 x number of cards) Bytes Sync 3 Checksum 1 Message ID 4 Message byte count 4 Week number 4 Seconds of week 8 Number of satellite channels 1 Number of signal channels 1 Number of cards 1 Reserved 1 CPU idle time, percent 4 Self-test status 4 Next Card offset =28 + (8 x card number) Format char char integer integer integer double char char char byte float integer Units weeks seconds Offset 0 3 4 8 12 16 24 25 26 27 28 32 NOTE: For Field 9, self-test bits 2, 3, 4, 6, & 7 are set only once (when the GPSCard is first powered up). All other bits are set by internal test processes each time the RVSB log is output. 194 MiLLennium Command Descriptions Manual D Logs summary SATA/B Satellite Specific Data This log provides satellite specific data for satellites actually being tracked. The record length is variable and depends on the number of satellites. Each satellite being tracked has a reject code indicating whether it is used in the solution, or the reason for its rejection from the solution. The reject value of 0 indicates the observation is being used in the position solution. Values of 1 through 11 indicate the observation has been rejected for the reasons specified in Table D-11. A range reject code of 8 only occurs when operating in differential mode and an interruption of corrections has occurred or the DGPSTIMEOUT has been exceeded. SATA Structure: $SATA week seconds sol status # obs azimuth elevation residual reject code prn azimuth elevation residual reject code *xx [CR][LF] prn : Field # Field type 1 2 3 4 5 6 7 $SATA week seconds sol status # obs prn azimuth 8 elevation 9 residual 10 reject code ... ... ... variable variable ... ... ... *xx [CR][LF] Data Description Log header GPS week number GPS seconds into the week Solution status as listed in Table D-1 Number of satellite observations with information to follow: Satellite PRN number (1-32) Satellite azimuth from user position with respect to True North, in degrees Satellite elevation from user position with respect to the horizon, in degrees Satellite range residual from position solution for each satellite, in metres Indicates that the range is being used in the solution (code 0) or that it was rejected (code 1-11), as shown in Table D-11 Next PRN number, azimuth, elevation, residual, reject code ... Last PRN number, azimuth, elevation, residual, reject code Checksum Sentence terminator Example $SATA 637 513902.00 0 7 18 168.92 5.52 9.582 0 *1F [CR][LF] Example: $SATA,637,513902.00,0,7,18,168.92,5.52,9.582,0,6,308.12,55.48,0.737,0, 15,110.36,5.87,16.010,0,11,49.63,40.29,-0.391,0, 2,250.05,58.89,-12.153,0,16,258.55,8.19,-20.237,0, 19,118.10,49.46,-14.803,0*1F[CR][LF] MiLLennium Command Descriptions Manual 195 D Logs summary SATB Format: Message ID =12 Field # Message byte count = 32 + (obs*32) Data Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer 4 Message byte count 4 integer 8 2 Week number 4 integer weeks 12 3 Seconds of week 8 double seconds 16 4 Solution status 4 integer 24 5 Number of observations (obs) 4 integer 28 6 PRN 4 integer 32 7 Azimuth 8 double degrees 36 8 Elevation 8 double degrees 44 9 Residual 8 double metres 52 10 Reject Code 4 integer 11... Next PRN offset = 32 + (obs*32) where obs varies form 0 to (obs-1) 60 Table D-11 GPSCard Range Reject Codes Value 0 1 2 3 4 5 6 7 8 9 10 11 12 13 196 Description Observations are good Bad satellite health is indicated by ephemeris data Old ephemeris due to data not being updated during last 3 hours Eccentric anomaly error during computation of the satellite’s position True anomaly error during computation of the satellite’s position Satellite coordinate error during computation of the satellite’s position Elevation error due to the satellite being below the cutoff angle Misclosure too large due to excessive gap between estimated and actual positions No differential correction is available for this particular satellite Ephemeris data for this satellite has not yet been received Invalid IODE due to mismatch between differential stations Locked Out: satellite is excluded by user (LOCKOUT command) Low Power: satellite rejected due to low signal/noise ratio L2 measurements are not currently used in the filter MiLLennium Command Descriptions Manual D Logs summary SBTA/B SATELLITE BROADCAST DATA: RAW SYMBOLS This message contains the satellite broadcast data in raw symbols before FEC decoding or any other processing. An individual message is sent for each PRN being tracked. For a given satellite, the message number increments by one each time a new message is generated. This data matches the RBTA/B data if the message numbers are equal. The data must be logged with the 'onnew' trigger activated to prevent loss of data. SBTA Structure: $SBTA week seconds raw symbols *xx prn cstatus message # # of symbols [CR][LF] Field # Field type Data Description Example 1 $SBTA Log header $SBTA 2 week GPS week number 883 3 seconds GPS seconds into the week 413908.000 4 prn PRN of satellite from which data originated 115 5 cstatus Channel Tracking Status 80812F14 6 message # Message sequence number 119300 7 # of symbols Number of symbols transmitted in the message. At present, always equals 256 symbols. 256 8 raw symbols 256 symbols compressed into a 128 bytes, i.e. 4 bits/symbol. Hence, 256 hex characters are output. If FEC decoding is enabled, soft symbols are output with values ranging from E to 3 where 3’s represent binary 1 and E’s represent binary 0 output. EE33EEEE33333E33EE33EEEE33 333E33EE33EEEE33333E33EE33E EEE33333EEEE3333EEE33E33E3 EE33EEE3EEEE33EE3E3EEEEEE EEEEEEEE3333EEE33EEEEE33E E3EEE3E3EE3EE33EEE33E333EE 3333E3E3333E33E3333EEEEE333 EE3E3333EE3EE3EE33EE3EE3EE 3E33E33E3EEE33333E3333E33E3 E333E3E33333E3EEE3E3E 9 *xx Checksum *4C 10 [CR][LF] Sentence terminator [CR][LF] SBTB Format: Message ID = 53 Field # Data Message byte count = 168 Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer Message byte count 4 integer bytes 8 2 Week number 4 integer weeks 12 3 Seconds of week 8 double seconds 16 4 PRN number 4 integer 1-999 24 5 Channel Status 4 integer n/a 28 6 Message # 4 integer n/a 32 7 # of Symbols 4 integer n/a 36 8 Raw Symbols 128 char n/a 40 MiLLennium Command Descriptions Manual 4 197 D Logs summary SPHA/B Speed and Direction Over Ground This log provides the actual speed and direction of motion of the GPSCard antenna over ground, at the time of measurement, and is updated up to 10 times per second. It should be noted that the GPSCard does not determine the direction a vessel, craft, or vehicle is pointed (heading), but rather the direction of motion of the GPS antenna relative to ground. SPHA Structure: $SPHA week vert spd Field # seconds hor spd sol status *xx Field type 1 2 3 4 5 $SPHA week seconds hor spd trk gnd 6 vert spd 7 8 9 sol status *xx [CR][LF] trk gnd [CR][LF] Data Description Example Log header GPS week number GPS seconds into the week Horizontal speed over ground, in metres per second Actual direction of motion over ground (track over ground) with respect to True North, in degrees Vertical speed, in metres per second, where positive values indicate increasing altitude (up) and negative values indicate decreasing altitude (down) Solution status as listed in Table D-1 Checksum Sentence terminator $SPHA 640 333111.00 0.438 325.034 2.141 0 *02 [CR][LF] Example: $SPHA,640,333111.00,0.438,325.034,2.141,0*02[CR][LF] SPHB Format: Field # 1 (header) 2 3 4 5 6 7 198 Message ID = 06 Message byte count = 52 Data Sync Checksum Message ID Message byte count Week number Seconds of week Horizontal speed Track over ground (TOG) Vertical speed Solution status Bytes 3 1 4 4 4 8 8 8 8 4 Format char char integer integer integer double double double double integer Units weeks seconds metres per second degrees metres per second Offset 0 3 4 8 12 16 24 32 40 48 MiLLennium Command Descriptions Manual D Logs summary SVDA/B SV Position in ECEF XYZ Coordinates with Corrections When combined with a RGEA/B/D log, this data set contains all of the decoded satellite information necessary to compute the solution: satellite coordinates (ECEF WGS84), satellite clock correction, ionospheric corrections (from broadcast model), tropospheric corrections (Hopfield model), decoded differential correction used and range weight standard deviation. The corrections are to be added to the pseudoranges. Only those satellites that are healthy are reported here. Also see the PXYA/B log, Figure D-2. SVDA Structure: week $SVDA prn seconds rec clk err # obs x y z clk corr ion corr trop corr diff corr rng std prn x y z clk corr ion corr trop corr diff corr rng std *xx [CR][LF] : Field # Field type 1 2 3 $SVDA week seconds 4 5 6 7 8 9 10 11 12 13 14 ... ... ... variable variable rec clk err # obs prn x y z clk corr ion corr trop corr diff corr rng std ... ... ... *xx [CR][LF] Data Description Log header GPS week number GPS seconds into the week (receiver time, not corrected for clock error, CLOCKADJUST enabled) Solved receiver clock error (metres) Number of satellite observations to follow Satellite PRN number (1-32) Satellite x coordinate (metres) Satellite y coordinate (metres) Satellite z coordinate (metres) Satellite clock correction (metres) Ionospheric correction (metres) Tropospheric correction (metres) Decoded differential correction used (metres) Range weight standard deviation (metres) Next PRN number, x, y, z, clk corr, ion corr, trop corr, diff corr, mg std ... Last PRN number, x, y, z, clk corr, ion corr, trop corr, diff corr, mg std Checksum Sentence terminator Example $SVDA 766 143860.00 -4.062 7 20 -15044774.225 -9666598.520 19499537.398 6676.013 -1.657 -2.662 16.975 0.674 *23 [CR][LF] Example: $SVDA,766,143860.00,-4.062,7, 20,-15044774.225,-9666598.520,19499537.398,6676.013,-1.657,-2.662,16.975,0.674 5,-10683387.874,-21566845.644,11221810.349,18322.228,-1.747,-2.819,-8.864,0.790, 6,-20659074.698,-28381.667,16897664619,57962.693,-2.543,4.401,-37.490,1.203, 16,142876.148,-26411452.927,2795075.561,-22644.136,-2.733,-4.904,7.701,1.259, 24,-852160.876,-16138149.057,21257323.813,229594.682,-1.545,-2.451,32.178,0.420, 25,-12349609.643,11102877.199,20644151.935,-4313.339,-3.584,-8.579, -42.813,1.370, .., 4,14209626.440,-9259502.647,20544348.215,12811.399,-2.675,-4.741,-10.778,1.239 *23[CR][LF] MiLLennium Command Descriptions Manual 199 D Logs summary SVDB Format: Field # 1 (header) 2 3 4 5 6 7 8 9 10 11 12 13 14 15... 200 Message ID = 36 Data Message byte count = 36 +(obs*68) Bytes Format Sync 3 char Checksum 1 char Message ID 4 integer Message byte count 4 integer Week number 4 integer Time in seconds 8 double Receiver clock error 8 double Number of observations to follow (obs) 4 integer Satellite PRN number 4 integer x coordinate of satellite 8 double y coordinate of satellite 8 double z coordinate of satellite 8 double Satellite clock correction 8 double Ionospheric correction 8 double Tropospheric correction 8 double Decoded differential correction used 8 double Range weight standard deviation 8 double Next PRN offset = 36 + (obs *68) where obs varies from 0 to (obs-1) Units weeks seconds metres metres metres metres metres metres metres metres metres Offset 0 3 4 8 12 16 24 32 36 40 48 56 64 72 80 88 96 MiLLennium Command Descriptions Manual D Logs summary TM1A/B Time of 1PPS This log provides the time of the GPSCard 1PPS, normally high, active low pulse (1 millisecond), where falling edge is reference, in GPS week number and seconds into the week. It also includes the receiver clock offset, the standard deviation of the receiver clock offset and clock model status. This log will output at a maximum rate of 1 Hz. TM1A Structure: $TM1A week utc offset seconds cm status Field # Field type 1 2 3 $TM1A week seconds 4 offset 5 6 offset std utc offset 7 cm status 8 9 *xx [CR][LF] offset *xx offset std [CR][LF] Data Description Example Log header GPS week number GPS seconds into the week at the epoch coincident with the 1PPS output strobe (receiver time) Receiver clock offset, in seconds. A positive offset implies that the receiver clock is ahead of GPS Time. To derive GPS time, use the following formula: GPS time = receiver time - (offset) Standard deviation of receiver clock offset, in seconds This field represents the offset of GPS time from UTC time, computed using almanac parameters. To reconstruct UTC time, algebraically subtract this correction from field 3 above (GPS seconds). UTC time = GPS time + (utc offset) Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that the model is in the process of stabilization Checksum Sentence terminator $TM1A 794 414634.99999996 6 -0.000000078 0.000000021 -9.999999998 0 *57 [CR][LF] Example: $TM1A,794,414634.999999966,-0.000000078,0.000000021,-9.999999998,0*57[CR][LF] TM1B Format: Field # 1 (header) 2 3 4 5 6 7 Message ID = 03 Data Sync Checksum Message ID Message byte count Week number Seconds of week Clock offset Stddev clock offset UTC offset Clock model status Message byte count = 52 Bytes 3 1 4 4 4 8 8 8 8 4 MiLLennium Command Descriptions Manual Format char char integer integer integer double double double double integer Units weeks seconds seconds seconds seconds Offset 0 3 4 8 12 16 24 32 40 48 201 D Logs summary VERA/B Receiver Hardware and Software Version Numbers This log contains the current hardware type and software version number for the GPSCard. Together with the RVSA/B log, it supersedes the RCSA/B log. VERA Structure: $VERA Field # week seconds version Field type *xx [CR][LF] Data Description Example 1 2 3 4 $VERA week seconds version Log header GPS week number GPS seconds into the week. GPSCard hardware type and software version number 5 6 *xx [CR][LF] Checksum Sentence terminator $VERA 853 401364.50 OEM-3 MILLENSTD CGL96170069 HW 3-1 SW 4.42/2.03 May 14/96 *2B [CR][LF] Example: $VERA,853,401364.50,OEM-3 MILLENSTD CGL96170069 HW 3-1 SW 4.42/2.03 May 14/ 96*2B[CR][LF] VERB Format: Field # 1 (header) 2 3 4 202 Message ID = 58 Data Sync Checksum Message ID Message byte count Week number Time into week Version numbers Message byte count = 104 Bytes 3 1 4 4 4 8 80 Format char char integer integer integer double char Units weeks s Offset 0 3 4 8 12 16 24 MiLLennium Command Descriptions Manual D Logs summary VLHA/B Velocity, Latency, and Direction over Ground This log is similar to the SPHA/B message. As in the SPHA/B messages the actual speed and direction of the GPSCard antenna over ground is provided. The VLHA/B differs in that it provides a measure of the latency in the velocity time tag and a new velocity status word which gives the user more velocity quality information. The velocity status indicates varying degrees of velocity quality. To ensure healthy velocity, the position sol-status must also be checked. If the sol-status is non-zero, the velocity will likely be invalid. Also, it includes the age of the differential corrections used in the velocity computation. It should be noted that the GPSCard does not determine the direction a vessel, craft, or vehicle is pointed (heading), but rather the direction of motion of the GPS antenna relative to ground. VLHA Structure: $VLHA week vert spd Field # seconds latency sol status vel status Field type 1 2 3 4 $VLHA week seconds latency 5 6 7 age hor spd trk gnd 8 vert spd 9 10 11 12 sol status vel status *xx [CR][LF] ➀ Velocity Latency ➀ age hor spd *xx trk gnd [CR][LF] Data Description Log header GPS week number GPS seconds into the week A measure of the latency in the velocity time tag in seconds. It should be subtracted from the time to give improved results. Age of Differential GPS data in seconds Horizontal speed over ground, in metres per second Actual direction of motion over ground (track over ground) with respect to True North, in degrees Vertical speed, in metres per second, where positive values indicate increasing altitude (up) and negative values indicate decreasing altitude (down) Solution status as listed in Table D-1 Velocity status as listed in Table D-12 Checksum Sentence terminator Example $VLHA 640 333111.00 0.250 3.500 0.438 325.034 2.141 0 0 *02 [CR][LF] The velocity is computed using Doppler values derived from differences in consecutive carrier phase measurements. As such, it is an average velocity based on the time difference between successive position computations and not an instantaneous velocity at the SPHA/B time tag. Under normal operation the position's coordinates are updated at a rate of two times per second. The velocity latency compared to this time tag will normally be 1/2 the time between position fixes. The default filter rate is 2 Hz, so this latency is typically 0.25 second, but if, for example, the POSA records were to be logged ontime 0.2, then the velocity latency would be one half of 0.2, or 0.1 second. The latency can be reduced further by the user requesting the POSA/B, the SPHA/B, or the VLHA/B messages at rates higher than 2 Hz. For example, a rate of 10 Hz will reduce the velocity latency to 1/20 of a second. For integration purposes, the velocity latency should be applied to the record time tag. Example: $VLHA,640,333111.00,0.250,3.500,0.438,325.034,2.141,0,0*02[CR][LF] MiLLennium Command Descriptions Manual 203 D Logs summary VLHB Format: Message ID = 34 Field # Message byte count = 72 Data 1 (header) Bytes Sync Checksum Message ID Message byte count Week number Seconds of week Latency Age Horizontal speed Track over ground (TOG) Vertical speed Solution status Velocity status 2 3 4 5 6 7 8 9 10 3 1 4 4 4 8 8 8 8 8 8 4 4 Format char char integer integer integer double double double double double double integer integer Units weeks seconds metres per second seconds metres per second degrees metres per second Offset 0 3 4 8 12 16 24 32 40 48 56 64 68 Table D-12 GPSCard Velocity Status Value 0 1 2 3 4 5 ➂ ➂ ➂ Description Velocity computed from differentially corrected carrier phase data Velocity computed from differentially corrected Doppler data Old velocity from differentially corrected phase or Doppler (higher latency) Velocity from single point computations Old velocity from single point computations (higher latency) Invalid velocity Higher values reserved for future use 204 MiLLennium Command Descriptions Manual D Logs summary WRCA/B Wide Band Range Correction (Grouped Format) This message contains the wide band range correction data. A correction is generated for each PRN being tracked and these group together into a single log. Internally, the correction for each satellite is updated asynchronously at a 1 Hz rate. Therefore, logging this message at a rate higher than 1 Hz will result in duplicate data being output. Each range correction is statistically independent and is derived from the previous 1 second of data. WRCA Structure: $WRCA prn week seconds # obs ch-tr-status tr-bandwidth wide band correction prn ch-tr-status tr-bandwidth wide band correction *xx [CR][LF] : Field # Field type Data Description Example 1 $WRCA Log header $WRCA 2 week GPS week number 637 3 seconds GPS seconds into the week 513902.00 4 # obs Number of satellite observations with information to follow: 7 5 prn Satellite PRN number 18 6 ch-tr-status Channel Tracking Status: Hexadecimal number indicating phase lock, channel number and channel tracking state as shown in Table D-7. E04 7 tr-bandwidth DLL tracking loop bandwidth in Hz 0.050 8 wide band correction Wide band range correction in metres 1.323 ... ... ... ... ... ... Next PRN number, ch-tr-status, tr-bandwidth, wide band correction ... Last PRN number, ch-tr-status, tr-bandwidth, wide band correction variable *xx Checksum *1F variable [CR][LF] Sentence terminator [CR][LF] WRCB Format: Message ID = 67 Field # Data Message byte count = 28 + (obs*16) Bytes Format Units Offset 1 Sync 3 char 0 (header) Checksum 1 char 3 Message ID 4 integer Message byte count 4 integer bytes 8 2 Week number 4 integer weeks 12 3 Seconds of week 8 double seconds 16 4 Number of observations (obs) 4 integer 24 5 PRN 4 integer 28 6 Channel tracking status 4 - - 32 7 DLL tracking loop bandwidth 4 float Hz 36 8 Wide Band Range Correction 4 float metres 40 9... Next PRN offset = 28 + (obs*16) MiLLennium Command Descriptions Manual 4 205 E Comparison Of RT-2 And RT-20 E COMPARISON OF RT-2 AND RT-20 E COMPARISON OF RT-2 AND RT-20 E.1 RT-2 & RT-20 PERFORMANCE RT-2 and RT-20 are real-time kinematic software products developed by NovAtel. They can only be used in conjunction with NovAtel GPS receivers. A quick comparison of RT-2 and RT-20 is shown in Table E-1: Table E-1 Comparison of RT-2 and RT-20 RT-2 GPS Frequencies Utilized Nominal Accuracy Lane Searching RT-20 L1 & L2 L1 2 cm (CEP) 20 cm (CEP) Wide lane and narrow lane None NovAtel’s RTK software algorithms utilize both carrier and code phase measurements; thus, the solutions are robust, reliable, accurate and rapid. While both RT-20 and RT-2 operate along similar principles, RT-2 achieves its extra accuracy and precision due to its being able to utilize dual-frequency measurements. Dual-frequency GPS receivers have two main advantages over their single-frequency counterparts when running RTK software: 1. 2. resolution of cycle ambiguity is possible due to the use of wide lane searching longer baselines are possible due to the removal of ionospheric errors The MiLLennium L1/L2 receivers are capable of transmitting RTK messages for both the GPSCard RT-20 and the MiLLennium RT-2 systems. Depending on the receiving receiver, it is capable of various levels of accuracy. Please refer to the particular accuracy as shown in Table E-2. Table E-2 RTK Messages Vs. Accuracy Transmitting (Reference) MiLLennium L1/L2 transmitting RTCA (i.e. RTCAOBS and RTCAREF) Receiving (Remote) MiLLennium L1/L2 receiver 100 metre 2DRMS MiLLennium RT-2 receiver 2 centimetre CEP GPSCard RT-20 receiver MiLLennium L1/L2 transmitting RTCM type 3 and 59 GPSCard RT-20 transmitting RTCM type 3 and 59 GPSCard RT-20 or MiLLennium L1/L2 transmitting RTCM or RTCA type 1 Accuracy Expected ➀ 20 centimetre CEP MiLLennium L1/L2 receiver 100 meter 2DRMS MiLLennium RT-2 receiver 20 centimetre CEP GPSCard RT-20 receiver 20 centimetre CEP MiLLennium L1/L2 receiver 100 meter 2DRMS MiLLennium RT-2 receiver 20 centimetre CEP GPSCard RT-20 receiver 20 centimetre CEP MiLLennium L1/L2 receiver 1 metre SEP MiLLennium RT-2 receiver 1 metre SEP GPSCard RT-20 receiver 1 metre SEP ➀ Not yet implemented in receiver firmware revision 3.34 206 MiLLennium Command Descriptions Manual E Comparison Of RT-2 And RT-20 RT-2 Performance The RT-2 software provides the accuracies shown in Table E-3 & Figure E-1 (static mode) and Table E-4 & Figure E-2 (kinematic mode) for “typical” multipath, ionospheric, tropospheric, and ephemeris errors, where “typical” is described as follows: • A typical multipath environment would provide no carrier-phase double-difference multipath errors greater than 2 cm or pseudorange double-difference multipath errors greater than 2 m on satellites at 11° elevation or greater. For environments where there is greater multipath, please consult NovAtel Customer Service. • Typical unmodeled ionospheric, tropospheric and ephemeris errors must be within 2σ of their average values, at a given elevation angle and baseline length. It is assumed that the tropospheric correction is computed with standard atmospheric parameters. All performance specifications assume that at least 6 satellites above the mask angle (varies between 11 and 14 degrees) are being tracked on both L1 and L2. All accuracy values refer to horizontal RMS error, and are based on matched positions. The level of position accuracy at any time will be reflected in the standard deviations output with the position. Table E-3 RT-2 Performance: Static Mode Baseline length Time since L2 lock-on with at least 6 satellites above mask angle Horizontal accuracy at the stated time Runs meeting the stated accuracy at the stated time < 10 km 70 seconds + 1.5 sec/km 2 cm + 0.5 ppm 75.0% < 10 km 5 minutes 1 cm + 1 ppm 75.0% < 15 km 4 minutes 5 cm 66.7% < 25 km 7 minutes 7 cm 66.7% < 35 km 10 minutes 35 cm 66.7% < 35 km 30 minutes 25 cm 66.7% Table E-4 RT-2 Performance: Kinematic Mode Baseline length Time since L2 lock-on with at least 6 satellites above mask angle Horizontal accuracy at the stated time Runs meeting the stated accuracy at the stated time < 10 km 120 seconds + 1.5 sec/km 2 cm + 0.5 ppm 75.0% < 15 km 8 minutes 8 cm 66.7% < 25 km 14 minutes 10 cm 66.7% < 35 km 20 minutes 40 cm < 35 km 60 minutes 25 cm MiLLennium Command Descriptions Manual 66.7% 66.7% 207 E Comparison Of RT-2 And RT-20 Figure E-1 Typical RT-2 Horizontal Convergence - Static Mode 1.4 1.2 Baselines CEP(meters) 1 0.1 km 15 km 0.8 25 km 50 km 1500 1800 0.6 0.4 0.2 0 0 300 600 900 1200 2100 2400 2700 3000 3300 3000 3300 Seconds of Convergence Figure E-2 Typical RT-2 Horizontal Convergence - Kinematic Mode 1.4 1.2 Baselines CEP(meters) 1 0.1 km 15 km 25 km 50 km 0.8 0.6 0.4 0.2 0 0 300 600 900 1200 1500 1800 2100 2400 2700 Seconds of Convergence 208 MiLLennium Command Descriptions Manual E Comparison Of RT-2 And RT-20 For baselines under 30 km long, the RT-2 solution shows two pronounced steps in accuracy convergence; these correspond to the single-point solution switching to the floating ambiguity solution which in turn switches to the narrow lane solution. If you were monitoring this using NovAtel’s GPSolution program, the convergence sequence might look something like what is shown in Figure E-3. Figure E-4 shows the performance of the RT-2 system running RTCM59 corrections at 1/2 Hz rate. Figure E-3 RT-2 Accuracy Convergence Single-point solution Floating ambiguity solution Narrow lane solution Figure E-4 Illustration of RT-2 Steady State Performance RT-20 Performance As shown in Table E-5, Figure E-5 and Figure E-6 the RT-20 system provides nominal 20 cm accuracy (CEP) after 3 minutes of continuous lock in static mode. After an additional period of continuous tracking (from 10 to 20 minutes), the system reaches steady state and position accuracies in the order of 3 to 4 cm are typical. The time to steady state is about 3 times longer in kinematic mode. RT-20 double-difference accuracies are based on PDOP < 2 and continuous tracking of at least 5 satellites (6 preferred) at elevations of at least 11.5°. All accuracy values refer to horizontal RMS error, and are based on low-latency positions. The level of position accuracy at any time will be reflected in the standard deviations output with the position. MiLLennium Command Descriptions Manual 209 E Comparison Of RT-2 And RT-20 Table E-5 RT-20 Performance Tracking Time (sec) Mode ① Data Delay (sec) Distance (km) Accuracy (CEP) 1 - 180 180 - 3000 > 3000 Static Static Static 0 0 0 1 1 1 100 to 25 cm 25 to 5 cm 5 cm or less 1 - 600 600 - 3000 > 3000 Kinematic Kinematic Kinematic Either Either Either Either Either Either Either Either 0 0 0 0-2 2-7 7 - 30 30 - 60 > 60 0 0 0 1 1 1 1 1 1 1 1 0 - 10 10 - 20 20 - 50 100 to 25 cm 25 to 5 cm 5 cm or less +1 cm/sec +2 cm/sec +5 cm/sec +7 cm/sec (single point) +0.5 cm/km +0.75 cm/km +1.0 cm/km ➁ ② ③ ① Mode = Static or Kinematic (during initial ambiguity resolution) ② The accuracy specifications refer to the PRTKA/B logs which include about 3 cm extrapolation error. RTKA/B logs are more accurate but have increased latency associated with them. ③ Between 30 and 60 seconds assumes pseudorange differential positioning. If Type 1 corrections have not been transmitted, the accuracy drops to single-point mode after 60 seconds. Figure E-5 Typical RT-20 Convergence - Static Mode 1.4 1.2 Baselines CEP(meters) 1 0.1 km 15 km 0.8 25 km 50 km 1500 1800 0.6 0.4 0.2 0 0 300 600 900 1200 2100 2400 2700 3000 3300 Seconds of Convergence 210 MiLLennium Command Descriptions Manual E Comparison Of RT-2 And RT-20 Figure E-6 Typical RT-20 Convergence - Kinematic Mode 1.4 Baselines 1.2 0.1 km 15 km CEP(meters) 1 25 km 50 km 1500 1800 0.8 0.6 0.4 0.2 0 0 300 600 900 1200 2100 2400 2700 3000 3300 Seconds of Convergence Figure E-7 shows the performance of the RT-20 system running with RTCM59 corrections received at a 1/2 Hz rate. Figure E-7 RT-20 Steady State Performance MiLLennium Command Descriptions Manual 211 E Comparison Of RT-2 And RT-20 E.2 PERFORMANCE CONSIDERATIONS When referring to the “performance” of RTK software, two factors are introduced: 1 Baseline length: the position estimate becomes less precise as the baseline length increases. Note that the baseline length is the distance between the phase centres of the two antennas. Identifying the exact position of your antenna’s phase centre is essential; this information is typically supplied by the antenna’s manufacturer or vendor. The RTK software automatically makes the transition between short and longer baselines, but the best results are obtained for baselines less than 10 km. The following are factors which are related to baseline length: • ephemeris errors - these produce typical position errors of 0.75 cm per 10 km of baseline length. • ionospheric effects - the dominant error for single-frequency GPS receivers on baselines exceeding 10 km. Differential ionospheric effects reach their peak at dusk and dawn, being at a minimum during hours of darkness. Ionospheric effects can be estimated and removed on dual-frequency GPS receivers, greatly increasing the permissible baseline length, but at the cost of introducing additional “noise” to the solution. Therefore, this type of compensation is only used in cases where the ionospheric error is much larger than the noise and multipath error. • tropospheric effects - these produce typical position errors of approximately 1 cm per 10 km of baseline length. This error increases if there is a significant height difference between the reference and remote stations, as well as if there are significantly different weather conditions between the two sites. A related issue is that of multipath interference, the dominant error on short differential baselines. Generally, multipath can be reduced by choosing the antenna’s location with care, and by the use of a choke-ring antenna ground plane, see Appendix B. 2. Convergence time: the position estimate becomes more accurate and more precise with time. However, convergence time is dependent upon baseline length: while good results are available after a minute or so for short baselines, the time required increases with baseline length. Convergence time is also affected by the number of satellites which can be used in the solution: the more satellites, the faster the convergence. Performance Degradation The performance will degrade if satellites are lost at the remote or if breaks occur in the differential correction transmission link. The degradations related to these situations are described in the following paragraphs. Provided lock is maintained on at least 4 SVs and steady state has been achieved, the only degradation will be the result of a decrease in the geometrical strength of the observed satellite constellation. If steady state has not been achieved, then the length of time to ambiguity resolution under only 4-satellite coverage will be increased significantly. REMOTE TRACKING LOSS If less than 4 satellites are maintained, then the RT-20 filter will be reset and all ambiguity information for all satellites (tracked or not) will be lost. When this occurs, the POSA/B and P20A/B logs will be generated with differential (if RTCM Type 1 messages are transmitted with the Type 59 messages) or single point pseudorange solutions. When the satellites are reacquired, the RT-20 initialization process described below occurs (see Figure E-8). DIFFERENTIAL LINK BREAKDOWN 1. 212 Provided the system is in steady state, and the loss of observation data is for less than 30 seconds, the RT-20 positions will degrade according to the divergence of the monitor observation extrapolation filters. This causes a decrease in accuracy of about an order of magnitude per 10 seconds without a monitor observation, and this degradation is reflected in the standard deviations of the POSA/B and P20A/B logs. Once the data link has been re-established, the accuracy will return to normal after several samples have been received. MiLLennium Command Descriptions Manual E Comparison Of RT-2 And RT-20 2. If the loss of differential corrections lasts longer than 30 seconds, the RT-20 filter is reset and all ambiguity and monitor model information is lost. The timeout threshold for RT-20 differential corrections is 30 seconds, but for Type 1 pseudorange corrections, the timeout is 60 seconds. Therefore, when the RT-20 can no longer function because of this timeout, the pseudorange filter can produce differential positions for an additional 30 seconds (provided RTCM Type 1 messages were transmitted along with the Type 59 messages) before the system reverts to single point positioning. Furthermore, once the link is reestablished, the pseudorange filter produces an immediate differential position while the RT-20 filter takes an additional 14 seconds to generate its positions. The monitor models require 7 monitor observations before they are declared useable, and this will take 14 seconds, based on a 1/2 Hz differential correction rate. The monitor model must be healthy before solutions are logged to the POSA/B and P20A/B logs, so there is a delay in the use of real time carrier positioning to the user once the link has been re-established. The RT20A/B log uses matched observations only (no extrapolated observations), and these will be available after three monitor observations are received, but will have about 1.5 seconds latency associated with them. Figure E-8 RT-20 Re-initialization Process REFERENCE REMOTE RTCM59 messages required following RESETRT20 1 2 3 4 5 Reference Start generating reference phase Doppler models and RTKA/B logs 6 Models Ready 7 Generate RTKA/B and PRTKA/B logs The RT-20 system is based on a time-matched double difference observation filter. This means that observations at the remote site have to be buffered while the monitor observation is encoded, transmitted, and decoded. Only two seconds of remote observations are saved, so the monitor observation transmission process has to take less than 2 seconds if any time matches are to be made. In addition, only remote observations on even second boundaries are retained, so monitor observations must also be sent on even seconds if time matches are to be made. MiLLennium Command Descriptions Manual 213 F Standards and References F F STANDARDS AND REFERENCES STANDARDS AND REFERENCES RTCM STANDARDS REFERENCE For detailed specifications of RTCM, refer to RTCM SC104 Version 2.1 of "RTCM Recommended Standards For Differential NAVSTAR GPS Service", January 3, 1994 Radio Technical Commission for Maritime Services 655 15th Street NW, Suite 300 Washington, D.C. 20005 U.S.A. Telephone: 202-639-4006 Fax: 202-347-8540 Website: http://www.navcen.uscg.mil/dgps/dgeninfo/RTCM104.txt RTCA STANDARDS REFERENCE For copies of the Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category-I (SCAT-I), contact: RTCA, Incorporated 1140 Connecticut Avenue N.W., Suite 1020 Washington, D.C. 20036-4001 U.S.A. Telephone: 202-833-9339 Fax: 202-833-9434 Website: http://www.rtca.org GPS SPS SIGNAL SPECIFICATION REFERENCE For copies of the Interface Control Document (ICD)-GPS-200, contact: ARINC Research Corporation 2551 Riva Road Annapolis, MD 21401-7465 Telephone: 410-266-4000 Fax: 410-266-4049 Website: http://www.arinc.com NMEA REFERENCE National Marine Electronics Association, NMEA 0183 Standard for Interfacing Marine Electronic Devices, Version 2.00, January 1, 1992 NMEA Executive Director P.O. Box 50040 Mobile, Alabama 36605 U.S.A. Website: http://www4.coastalnet.com/nmea GEODETIC SURVEY OF CANADA Geodetic Survey of Canada 615 Boothe Street Ottawa, Ontario K1A 0E9 Telephone: (613) 995-4410 Fax: (613)995-3215 Website: http://www.geod.emr.ca U.S. NATIONAL GEODETIC SURVEY NGS Information Services 1315 East-West Highway Station 9244 Silver Springs, MD 20910-3282 Telephone: (301)713-2692 Fax: (301)713-4172 Website: http://www.ngs.noaa.gov Note: 214 Website addresses may be subject to change however they are accurate at the time of publication. MiLLennium Command Descriptions Manual G Geodetic Datums G GEODETIC DATUMS G GEODETIC DATUMS The following tables contain the internal ellipsoid parameters and transformation parameters used in the GPSCard. The values contained in these tables were derived from the following DMA technical reports: 1. TR 8350.2 Department of Defence World Geodetic System 1984 and Relationships with Local Geodetic Systems - Revised March 1, 1988. 2. TR 8350.2B Supplement to Department of Defence World Geodetic System 1984 Technical Report - Part II - Parameters, Formulas, and Graphics for the Practical Application of WGS84 - December 1, 1987. Table G-1 Reference Ellipsoid Constants ELLIPSOID ID CODE Airy 1830 Modified Airy Australian National Bessel 1841 Clarke 1866 Clarke 1880 Everest (India 1830) Everest (Brunei & E.Malaysia) Everest (W.Malaysia & Singapore) Geodetic Reference System 1980 Helmert 1906 Hough 1960 International 1924 South American 1969 World Geodetic System 1972 World Geodetic System 1984 a (metres) AW AM AN BR CC CD EA EB ED RF HE HO IN SA WD WE 6377563.396 6377340.189 6378160.0 6377397.155 6378206.4 6378249.145 6377276.345 6377298.556 6377304.063 6378137.0 6378200.0 6378270.0 6378388.0 6378160.0 6378135.0 6378137.0 1/f 299.3249647 299.3249647 298.25 299.1528128 294.9786982 293.465 300.8017 300.8017 300.8017 298.257222101 298.30 297.00 297.00 298.25 298.26 298.257223563 f 0.00334085064038 0.00334085064038 0.00335289186924 0.00334277318217 0.00339007530409 0.00340756137870 0.00332444929666 0.00332444929666 0.00332444929666 0.00335281068118 0.00335232986926 0.00336700336700 0.00336700336700 0.00335289186924 0.00335277945417 0.00335281066475 Table G-2 Transformation Parameters (Local Geodetic to WGS84) GPSCard Datum ID number NAME DX DY DZ DATUM DESCRIPTION ELLIPSOID 1 ADIND -162 -12 206 Adindan (Ethiopia, Mali, Senegal & Sudan) Clarke 1880 2 ARC50 -143 -90 -294 ARC 1950 (SW & SE Africa) Clarke 1880 3 ARC60 -160 -8 -300 ARC 1960 (Kenya, Tanzania) Clarke 1880 4 AGD66 -133 -48 148 Australian Geodetic Datum 1966 Australian National 5 AGD84 -134 -48 149 Australian Geodetic Datum 1984 Australian National 6 BUKIT -384 664 -48 Bukit Rimpah (Indonesia) Bessel 1841 7 ASTRO -104 -129 239 Camp Area Astro (Antarctica) International 1924 8 CHATM 175 -38 113 Chatum 1971 (New Zealand) International 1924 9 CARTH -263 6 431 Carthage (Tunisia) Clarke 1880 10 CAPE -136 -108 -292 CAPE (South Africa) Clarke 1880 11 DJAKA -377 681 -50 Djakarta (Indonesia) Bessel 1841 12 EGYPT -130 110 -13 Old Egyptian Helmert 1906 13 ED50 -87 -98 -121 European 1950 International 1924 14 ED79 -86 -98 -119 European 1979 International 1924 15 GUNSG -403 684 41 G. Segara (Kalimantan - Indonesia) Bessel 1841 MiLLennium Command Descriptions Manual 215 G Geodetic Datums Table G-2 Transformation Parameters (Local Geodetic to WGS84) 16 GEO49 84 -22 209 Geodetic Datum 1949 (New Zealand) International 1924 17 GRB36 375 -111 431 Great Britain 1936 (Ordinance Survey) Airy 1830 18 GUAM -100 -248 259 Guam 1963 (Guam Island) Clarke 1866 19 HAWAII 89 -279 -183 Hawaiian Hawaii (Old) International 1924 20 KAUAI 45 -290 -172 Hawaiian Kauai (Old) International 1924 21 MAUI 65 -290 -190 Hawaiian Maui (Old) International 1924 22 OAHU 56 -284 -181 Hawaiian Oahu (Old) International 1924 23 HERAT -333 -222 114 Herat North (Afghanistan) International 1924 24 HJORS -73 46 -86 Hjorsey 1955 (Iceland) International 1924 25 HONGK -156 -271 -189 Hong Kong 1963 International 1924 26 HUTZU -634 -549 -201 Hu-Tzu-Shan (Taiwan) International 1924 27 INDIA 289 734 257 Indian (India, Nepal, Bangladesh) Everest (EA) 28 IRE65 506 -122 611 Ireland 1965 Modified Airy 29 KERTA -11 851 5 Kertau 1948 (West Malaysia and Singapore) Everest (ED) 30 KANDA -97 787 86 Kandawala (Sri Lanka) Everest (EA) 31 LIBER -90 40 88 Liberia 1964 Clarke 1880 32 LUZON -133 -771 -51 Luzon (Philippines excluding Mindanoa Is.) Clarke 1866 33 MINDA -133 -70 -72 Mindanoa Island Clarke 1866 34 MERCH 31 146 47 Merchich (Morocco) Clarke 1880 35 NAHR -231 -196 482 Nahrwan (Saudi Arabia) Clarke 1880 36 NAD83 0 0 0 N. American 1983 (Includes Areas 37-42) GRS-80 37 CANADA -10 158 187 N. American Canada 1927 Clarke 1866 38 ALASKA -5 135 172 N. American Alaska 1927 Clarke 1866 39 NAD27 -8 160 176 N. American Conus 1927 Clarke 1866 40 CARIBB -7 152 178 N. American Caribbean Clarke 1866 41 MEXICO -12 130 190 N. American Mexico Clarke 1866 42 CAMER 0 125 194 N. American Central America Clarke 1866 43 MINNA -92 -93 122 Nigeria (Minna) Clarke 1880 44 OMAN -346 -1 224 Oman Clarke 1880 45 PUERTO 11 72 -101 Puerto Rica and Virgin Islands Clarke 1866 46 QORNO 164 138 -189 Qornoq (South Greenland) International 1924 47 ROME -255 -65 9 Rome 1940 Sardinia Island International 1924 48 CHUA -134 229 -29 South American Chua Astro (Paraguay) International 1924 49 SAM56 -288 175 -376 South American (Provisional 1956) International 1924 50 SAM69 -57 1 -41 South American 1969 S. American 1969 51 CAMPO -148 136 90 S. American Campo Inchauspe (Argentina) International 1924 52 SACOR -206 172 -6 South American Corrego Alegre (Brazil) International 1924 53 YACAR -155 171 37 South American Yacare (Uruguay) International 1924 54 TANAN -189 -242 -91 Tananarive Observatory 1925 (Madagascar) International 1924 55 TIMBA -689 691 -46 Timbalai (Brunei and East Malaysia) 1948 Everest (EB) 56 TOKYO -128 481 664 Tokyo (Japan, Korea and Okinawa) Bessel 1841 57 TRIST -632 438 -609 Tristan Astro 1968 (Tristan du Cunha) International 1924 58 VITI 51 391 -36 Viti Levu 1916 (Fiji Islands) Clarke 1880 59 WAK60 101 52 -39 Wake-Eniwetok (Marshall Islands) Hough 1960 60 WGS72 0 0 4.5 World Geodetic System - 72 WGS72 61 WGS84 0 0 0 World Geodetic System - 84 WGS84 62 ZANDE -265 120 -358 Zanderidj (Surinam) International 1924 63 USER 0 0 0 User Defined Datum Defaults User * 216 MiLLennium Command Descriptions Manual G Geodetic Datums Notes: * Default user datum is WGS84. * Also see the DATUM and USERDATUM commands in Chapter 2 and Appendix C. * The GPSCard DATUM command sets the Datum value based on the name entered as listed in the "NAME" column in Table G-2 (e.g., NAD83). * The following GPSCard logs report Datum used according to the "GPSCard Datum ID" column: B, PRTKA/B, RTKA/B, and MKPA/B. MiLLennium Command Descriptions Manual POSA/ 217 H Some Common Unit Conversions H SOME COMMON UNIT CONVERSIONS H SOME COMMON UNIT CONVERSIONS Listed below are several commonly used equivalents between the SI (Système Internationale) units of weights and measures used in the metric system, and those used in the imperial system. Distance 1 metre (m) = 100 centimetres (cm) = 1000 millimetres (mm) Volume 1 kilometre (km) = 1000 metres (m) 1 litre (l) = 1000 cubic centimetres (cc) 1 international foot = 0.3048 metre 1 gallon (British) = 4.546 litres 1 US survey foot = 0.3048006096 metre 1 gallon (US) = 3.785 litres 1 statute mile = 1609 metres 1 nautical mile = 1852 metres Temperature Weight degrees Celsius = (5/9) x [(degrees Fahrenheit) - 32] 1 kilogram (kg) = 1000 grams degrees Fahrenheit = [(9/5) x (degrees Celsius)] + 32 1 pound = 0.4536 kilogram (kg) GPS Time of Week to Calendar Day (example) 511200 seconds Day 511200 / 86400 seconds per day = 5.916666667 days Hour .916666667 x 86400 / 3600 seconds per hour = Minute .000 x 3600 / 60 seconds per minute = Second .000 x 60 = 22.0000 hours 0.000 minutes 0.00 seconds Day 5 (Thursday) + 22 hours, 0 minutes, 0 seconds into Friday. Calendar Date to GPS Time (example: January 22, 1995 at 11:30 hours) Days from January 6, 1980 to January 22, 1995 = 15 years x 365 days /year = 5475 days Add one day for each leap year (a year which is divisible by 4 or 400 but not by 100; every 100 years a leap year is skipped) 4 days Days into 1997 (22nd is not finished) 21 days Total days 5500 days Deduct 5 days: Jan. 1 through 5, 1980 GPS Week: 5495 days 5495 x 86400 seconds per day = Seconds into week 22nd day: GPS time of week: Week 785, 41400 second 218 474768000 seconds/ 604800 sc per week = 785 11.5 hrs x 3600 sec/hr 41400 seconds MiLLennium Command Descriptions Manual I Information Messages INFORMATION MESSAGES I I INFORMATION MESSAGES TYPE 1 INFORMATION MESSAGES To date, the only Type 1 messages are the !ERRA and the !MSGA logs. !ERRA !ERRA Field # 1 2 3 4 5 6 7 type severity error string Field type !ERRA type severity error string opt. description *xx [CR][LF] opt. description *xx [CR][LF] Data Description Log header Log type, numbered 0 - 999 (see Table I-1) Only one is defined to date: severity_fatal (number = 0); causes reset Error message (see Table I-1) Optional description Checksum Sentence terminator Example: !ERRA,1,0,Authorization Code Invalid,*22[CR][LF] Table I-1 Type 1 !ERRA Types Log type 0 1 2 3 4 5 6 7+ Error String Unknown ERRA Type Authorization Code Invalid No Authorization Code Found Invalid Expiry In Authorization Code Unable To Read ESN Reserved For Future Use Card Has Stopped Unexpectedly Reserved For Future Use !MSGA !MSGA Field # 1 2 3 4 5 6 type message opt. description Field type !MSGA type message opt. description *xx [CR][LF] *xx [CR][LF] Data Description Log header Log type, numbered from 1000 (see Table I-2) Message (see Table I-2) Optional description Checksum Sentence terminator Example: !MSGA,1001,Authorization Code Is Time Limited, Model 3951R Expires on 960901*6C[CR][LF] MiLLennium Command Descriptions Manual 219 I Information Messages Table I-2 Type 1 !MSGA Types Log type 1000 1001 1002+ Message String Unknown MSGA Type Authorization Code Is Time Limited Reserved For Future Use TYPE 2 INFORMATION MESSAGES The following is a list of information messages which are generated by the Command Interpreter in response to a user’s input. This list is not necessarily complete, but it is the most accurate one available at the time of publication. It is intended to be a trouble-shooting tool. Error Message Meaning All Ok Argument Must Be Hexadecimal (0-9,A-F) Pairs Argument Must Be Numeric Authorization Changes Not Available On This Card No errors to report. An argument which is not hexadecimal was entered. An argument which is not numeric was entered. An attempt has been made to change the Authorization Code on a card which is not an OEM card. The checksum is incorrect for the Authorization Code. The Authorization Code was most likely entered incorrectly. The existing Authorization Code is invalid. Please contact NovAtel GPS customer service for a new Authorization Code. The existing Authorization Code cannot be changed. Please contact NovAtel GPS customer service for assistance. The clock model status in a $TM1A command is invalid. The $TM1A command is rejected when the clock model has not been set. The CLOCKADJUST command is not available on this model. Authorization Code Entered Incorrectly Authorization Code Is Invalid Can't Change Authorization Code Clock Model not set TM1A rejected CLOCK_ADJUST Command Not Available On This Model Complete Almanac not received yet - try again later Data Too Large To Save To NVM Differential Corrections Not Available On This Model EXTERNALCLOCK Command Not Available On This Model FREQUENCY_OUT Command Not Available On This Model FROM port name too LONG Invalid $ALMA CheckSum Invalid $DCSA CheckSum Invalid $DEBUG Options Invalid $IONA CheckSum Invalid $PXYA CheckSum Invalid $REPA CheckSum Invalid $RTCA CheckSum/CRC Invalid $RTCM CheckSum Invalid $TM1A CheckSum Invalid $UTCA CheckSum Invalid $VXYA CheckSum Invalid ADJUSTCLOCK Option Invalid Baudrate Invalid Carrier Smoothing Constant 220 The almanac cannot be saved because a complete almanac has not yet been received. A SAVEALMA command should be performed at a later time when a complete almanac has been received. The configuration data being saved is too large. This model does not have the ability to send or receive differential corrections. The EXTERNALCLOCK command is not available on this model. The FREQUENCY_OUT command is not available on this model. The FROM port name in a SETNAV command is too long. The checksum of a $ALMA command is invalid. The checksum of a $DCSA command is invalid. An invalid option was entered in the $DEBUG command. The checksum of a $IONA command is invalid. The checksum of a $PXYA command is invalid. The checksum of a $REPA command is invalid. The CRC of a $RTCA command is invalid. The checksum of a $RTCA command is invalid. The checksum of a $TM1A command is invalid. The checksum of a $UTCA command is invalid. The checksum of a $VXYA command is invalid. An invalid CLOCKADJUST switch has been entered. The bit rate in a COMn command is invalid. The carrier smoothing constant of the CSMOOTH command is invalid. MiLLennium Command Descriptions Manual I Information Messages Invalid Channel Number Invalid Coarse Modulus Field Invalid Command CRC Invalid Command Name Invalid Command Option Invalid Coordinates Invalid Datatype Invalid Datum Offset Invalid DATUM Option Invalid Datum Rotation Invalid Degree Field Invalid DGPS time-out value Invalid Doppler Invalid Doppler Window Invalid DTR choice Invalid DTR Toggle Option Invalid DTR Toggle Setup Time (0-1000) Invalid DTR Toggle Terminate Time (0-1000) Invalid DYNAMICS Option Invalid Echo Option Invalid Elevation Cutoff Angle Invalid ERRMSG Flag Invalid ERRMSG Port Invalid EXTERNALCLOCK Option Invalid EXTERNALCLOCK USER Argument(s) Invalid Fine Modulus Field Invalid FIX Option Invalid Flattening Invalid Handshake Option Invalid HEALTH Override Invalid Height Invalid Logger Datatype Invalid Logger Offset Invalid Logger Period Invalid Logger Port Option Invalid Logger Trigger Invalid Magnetic Variation Invalid Number of $ALMA Arguments Invalid Number of $DCSA Arguments Invalid Number of $IONA Arguments Invalid Number of $PXYA Arguments Invalid Number of $REPA Arguments Invalid Number of $TM1A Arguments Invalid Number of $UTCA Arguments Invalid Number of $VXYA Arguments Invalid Number of Arguments Invalid Number of Databits Invalid Number of StopBits Invalid Parity Option An invalid channel number has been entered in a command such as ASSIGN. The coarsemod argument of the FREQUENCY_OUT command is invalid. The received command has an invalid checksum. An invalid command name has been received. One or more arguments of a command are invalid. Invalid coordinates received in a command such as $PVCA, $PXYA, etc. The data type in an ACCEPT command is invalid. The datum offset in a USERDATUM command is invalid. An option in a DATUM command is invalid. The datum rotation angle in a USERDATUM command is invalid. An invalid degree field has been entered in a command such as FIX POSITION or SETNAV. An invalid timeout value was entered in the DGPSTIMEOUT command. An invalid Doppler has been entered in an ASSIGN command. An invalid Doppler window has been entered in an ASSIGN command. An invalid option was entered in the COMn_DTR command. The active option in the COMn_ DTR command is invalid. The lead time option in the COMn_ DTR command is invalid. The tail time option in the COMn_ DTR command is invalid. The option in a DYNAMICS command is invalid. The echo option in a COMn command is invalid. The elevation cutoff angle in an ECUTOFF command is invalid. The option (on/off) specified in a MESSAGE command is invalid. The port specified in a MESSAGE command is invalid. An invalid external clock was entered in the EXTERNALCLOCK command. An invalid argument was entered in the EXTERNALCLOCK command. The finemod argument of the FREQUENCY_OUT command is invalid. An option other than height, position or velocity was specified in a FIX command. The flattening in a USERDATUM command is invalid. The handshake option in a COMn command is invalid. An invalid health has been entered in a SETHEALTH or FIX command. The height in a FIX HEIGHT command is invalid. An invalid log has been specified in a LOG/UNLOG command. An invalid offset has been specified in a LOG command. An invalid period has been specified in a LOG command. An invalid port number has been specified in a LOG/UNLOG command. An invalid trigger has been specified in a LOG command. The magnetic variation in a MAGVAR command is invalid. The number of arguments in a $ALMA command is invalid. The number of arguments in a $DCSA command is invalid. The number of arguments in a $IONA command is invalid. The number of arguments in a $PXYA command is invalid. The number of arguments in a $REPA command is invalid. The number of arguments in a $TM1A command is invalid. The number of arguments in a $UTCA command is invalid. The number of arguments in a $VXYA command is invalid. A command has been received which has an invalid number of arguments. The number of data bits in a COMn command is invalid. The number of stop bits in a COMn command is invalid. The parity in a COMn command is invalid. MiLLennium Command Descriptions Manual 221 I Information Messages Invalid Port Invalid Port number Invalid PPS Modulus Field Invalid RINEX Option Invalid RTCA option Invalid RTCA station Name (\XXXX\) Invalid RTCM Bit Rule Invalid RTCM station Name (0..1023) Invalid RTCM16T string length - maximum 90 Invalid RTS choice Invalid RTS Toggle Option Invalid RTS Toggle Setup Time (0-1000) Invalid RTS Toggle Terminate Time (0-1000) Invalid Satellite Number Invalid Scaling Invalid Seconds Into Week in TM1A Invalid SemiMajor Axis Invalid Standard Deviation Limit (0.1-100 m) Invalid Symbol Period 1,2,4,5,10,20 Invalid Time Limit (0.1-100 hours) Invalid Token Invalid Track Offset Invalid Velocity Invalid Week Number in TM1A MET Command Not Available On This Model Model Invalid NVM Error - Unable To Save RINEX string too LONG RT20 Logs Not Available On This Model RTCM9 Logs Not Available On This Model SAVE Command Not Available On This Model Save Complete SETCLOCK disabled TM1A rejected Standard Deviation not allowed with small time limits TO Portname too LONG User Defined DATUM Not Set Valid Option but Missing Process 222 The port in a SEND command is invalid. The port number in an ACCEPT command is invalid. The ppsmod argument of the FREQUENCY_OUT command is invalid. An option of a RINEX command is invalid. An invalid RTCA rule has been entered. The RTCA station name in a FIX POSITION message is invalid. An invalid RTCM rule has been entered. The RTCM station name in a FIX POSITION message is invalid. The RTCM16T string exceeds 90 characters. An invalid option was entered in the COMn_RTS command. The active option in the COMn_RTS command is invalid. The lead time option in the COMn_RTS command is invalid. The tail time option in the COMn_RTS command is invalid. An invalid satellite number has been entered in an ASSIGN, SETHEALTH, LOCKOUT or UNLOCKOUT command. The scale value in a USERDATUM command is invalid. The time in a $TM1A command is invalid. The semi-major axis in a USERDATUM command is invalid. A standard deviation in a POSSE command is invalid. The symbol period is invalid for an ASSIGN on a pseudolite channel. The averaging time in a POSAVE command is invalid. This error should never occur. If it does, please contact NovAtel GPS customer service. The track offset in the SETNAV command is invalid. An invalid velocity has been received, either in a FIX VELOCITY command, or in a command such as $PVCA, $PVCB. The week in a $TM1A command is invalid. The MET command is not available on this model. The Authorization Code has an invalid Model. Please contact NovAtel GPS customer service for assistance. The SAVE operation did not complete successfully. Indicates that the entered RINEX command is too long. This model does not have the ability to send or receive RT20 differential corrections. This model does not have the ability to send or receive RTCM9 logs. A SAVE operation was attempted which is not available on this model. The SAVE operation completed successfully. The $TM1A command is rejected because the user has not enabled clock synchronization using the SETCLOCK command. In a POSAVE command, a standard deviation cannot be entered with a small time. Enter a larger averaging time if standard deviations are desired. The TO port name in a SETNAV command is too long. This error should not occur. By default the user defined DATUM is set to WGS84. If you get this error message, please contact NovAtel GPS customer service. This message indicates an error in the software. A command option is valid but software cannot process it MiLLennium Command Descriptions Manual J Listing Of Tables J LISTING OF TABLES J LISTING OF TABLES This section is provided for ease of reference. The tables reproduced in the pages that follow are: 1-1 1-2 2-1 2-2 4-1 4-2 6-1 C-1 C-2 C-3 D-1 D-2 D-3 D-4 D-5 D-6 D-7 D-8 D-9 D-10 D-11 D-12 E-1 E-2 E-3 E-4 E-5 GPSCard Pseudorange Differential Initialization Summary Latency - Induced Extrapolation Error Commands Table GPSCard Command Summary Chart Logs Table GPSCard Log Summary Positioning Modes Antenna LNA Power Configuration Default Values of Process Noise Elements VARF Range GPSCard Solution Status Position Type RTK Status For Position Type 3 (RT-20) RTK Status For Position Type 4 (RT-2) Receiver Self-Test Status Codes Range Record Formats (RGED only) Channel Tracking Status Ambiguity Types Searcher Status RTK Status GPSCard Range Reject Codes GPSCard Velocity Status Comparison of RT-2 and RT-20 RTK Messages Vs. Accuracy RT-2 Performance - Static Mode RT-2 Performance - Kinematic Mode RT-20 Performance MiLLennium Command Descriptions Manual 223 J Listing Of Tables Table 1-1 GPSCard Pseudorange Differential Initialization Summary REFERENCE MONITOR STATION Required: REMOTE STATION Required: FIX POSITION lat lon hgt id (health) LOG port DATATYPE ontime 5 Recom m ended Options: ACCEPT port DATATYPE Recom m ended Options: (binary): RTCMB RTCAB RTCM RTCA ACCEPT DATATYPES (binary): RTCM RTCA (ascii): RTCMA RTCAA Related Com m ands /Logs: RTCMRULE DATUM ACCEPT COM M ANDS (ascii): RTCMA RTCAA LOG DATATYPES LOG DATATYPES Related Com m ands /Logs: RTCMRULE DATUM POSA/B VLHA/B CDSA/B GPGGA Exam ple 1: Exam ple 1: accept com2 rtcm log com1 posa ontime 1 fix position 51.3455323 -114.2895345 1201.123 555 0 log com1 RTCM ontime 2 Exam ple 2: Exam ple 2: accept com2 commands log com1 posa ontime 0.2 log com1 vlha ontime 0.2 fix position 51.3455323 -114.2895345 1201.123 555 log com2 rtcaa ontime 2 NOTES: Italicized entries indicate user definable. Table 1-2 Latency-Induced Extrapolation Error Time since last reference station observation Typical extrapolation error (CEP) 0-2 seconds 2-7 seconds 7-30 seconds 1 cm/sec 2 cm/sec 5 cm/sec 224 MiLLennium Command Descriptions Manual J Listing Of Tables Table 2-1 Commands By Function Table COMMUNICATIONS, CONTROL AND STATUS Commands Descriptions ANTENNAPOWER Power to the low-noise amplifier of an active antenna COMn COMn_DTR COMn port configuration control DTR handshaking control COMn_RTS RTS handshaking control DIFF_PROTOCOL FREQUENCY_OUT Differential Protocol Control Variable frequency output (programmable) LOG MESSAGES Logging control Disable error reporting from command interpreter RINEX Configure the user defined fields in the file header RTCMRULE RTCM16T Sets up RTCM bit rule Enters an ASCII message SEND SENDHEX Sends ASCII message to COM port Sends non-printable characters SETL1OFFSET Add an offset to the L1 psuedorange to compensate for signal delays GENERAL RECEIVER CONTROL AND STATUS Commands Descriptions $ALMA CRESET Download almanac data file Reset receiver to factory default DYNAMICS HELP Set correlator tracking bandwidth On-line command help RESET Performs a hardware reset (OEM only) SAVEALMA Saves the latest almanac in NVM SAVECONFIG Saves current configuration (OEM only) $TM1A VERSION Injects receiver time of 1 PPS Software/hardware information POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL Commands Descriptions CSMOOTH DATUM Sets amount of carrier smoothing Choose a DATUM name type ECUTOFF Satellite elevation cut-off for solutions FIX HEIGHT FIX POSITION Constrains to fixed height (2D mode) Constrains to fixed lat, lon, height FRESET $IONA Clears all data which is stored in NVM Download ionospheric correction data LOCKOUT Deweights a satellite in solutions $PVAA RTKMODE Position, velocity and acceleration in ECEF coordinates Setup the RTK mode UNDULATION USERDATUM Ellipsoid-geoid separation User-customized datum MiLLennium Command Descriptions Manual 225 J Listing Of Tables Table 2-1 Commands By Function Table (continued) SATELLITE TRACKING AND CHANNEL CONTROL Commands Descriptions $ALMA Download almanac data file ASSIGN CONFIG Satellite channel assignment Switches the channel configuration of the GPSCard DYNAMICS Sets correlator tracking bandwidth FIX VELOCITY RESETHEALTH Aids high velocity reacquisition Reset PRN health SETHEALTH Overrides broadcast satellite health WAYPOINT NAVIGATION Commands Descriptions MAGVAR Magnetic variation correction SETNAV Waypoint input DIFFERENTIAL REFERENCE STATION Commands Descriptions DGPSTIMEOUT FIX POSITION Sets ephemeris delay Constrain to fixed (reference) LOG Selects required differential-output log POSAVE Implements position averaging for reference station RTCMRULE Selects RTCM bit rule SETDGPSID Set reference station ID DIFFERENTIAL REMOTE STATION Commands Descriptions ACCEPT Accepts RTCM, RTCA or RTCAB differential inputs $ALMA DGPSTIMEOUT Input almanac data Set maximum age of differential data accepted RESET Performs a hardware reset $RTCA RTCA differential correction input (ASCII) $RTCM RTCM differential correction input (ASCII) RTCMRULE SETDGPSID Selects RTCM bit rule Select differential reference station ID to receive POST PROCESSING DATA Commands Descriptions Depends on operating platform CLOCK INFORMATION, STATUS, AND TIME Commands CLOCKADJUST Descriptions EXTERNALCLOCK EXTERNALCLOCK FREQUENCY Enable clock modelling & 1PPS adjust Sets default parameters of an optional external oscillator Sets clock rate SETTIMESYNC Enable or disable time synchronization $UTCA Download UTC data 226 MiLLennium Command Descriptions Manual J Listing Of Tables Table 2-2 GPSCard Command Summary Command $ALMA $IONA $PVAA $REPA $RTCA $RTCM $TM1A $UTCA ACCEPT ANTENNAPOWER ASSIGN UNASSIGN UNASSIGNALL CLOCKADJUST COMn COMn_DTR COMn_RTS CONFIG CRESET CSMOOTH DATUM USERDATUM DGPSTIMEOUT DIFF_PROTOCOL DYNAMICS ECUTOFF EXTERNALCLOCK EXTERNALCLOCK FREQUENCY FIX HEIGHT FIX POSITION FIX VELOCITY UNFIX FREQUENCY_OUT FRESET HELP or ? LOCKOUT UNLOCKOUT UNLOCKOUTALL LOG UNLOG UNLOGALL Description Injects almanac Injects ionospheric refraction corrections Injects latest computed position, velocity and acceleration Injects raw GPS ephemeris data Injects RTCA format DGPS corrections in ASCII (Type 1) Injects RTCM format differential corrections in ASCII (Type 1) Injects receiver time of 1 PPS Injects UTC information Port input control (set command interpreter) Power to the low-noise amplifier of an active antenna Assign a prn to a channel # Un-assign a channel Un-assign all channels Disable clock steering mechanism Initialize Serial Port (1 or 2) Programmable DTR lead/tail time Programmable RTS lead/tail time Switches the channel configuration of the GPSCard Configuration reset to factory default Sets carrier smoothing Choose a DATUM name type User defined DATUM Sets maximum age of differential data to be accepted and ephemeris delay Differential correction message encoding and decoding for implementation in the GPS card firmware Set receiver dynamics Set elevation cutoff angle Sets default parameters of an optional external oscillator Sets clock rate Sets height for 2D navigation Set antenna coordinates for reference station Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of SVs Remove all receiver FIX constraints Variable frequency output (programmable) Clears all data which is stored in non-volatile memory On-line command help Lock out satellite Restore satellite Restore all satellites Choose data logging type Disable a data log Disable all data logs MiLLennium Command Descriptions Manual Syntax (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) (follows NovAtel ASCII log format) accept port,option antennapower flag assign channel,prn,doppler, search window unassign channel unassignall clockadjust switch comn bps,parity,databits,stopbits, handshake,echo comn_dtr control,active,lead,tail comn_rts control,active,lead,tail config cfgtype creset csmooth value datum option userdatum semi-major,flattening,dx,dy,dz, rx,ry,rz, scale dgpstimeout value value diff_protocol type key or diff_protocol disable or diff_protocol dynamics option [user_dynamics] ecutoff angle externalclock option external frequency clock rate fix height height [auto] fix position lat,lon,height [station id] [health] fix velocity vx,vy,vz unfix frequency_out n,k freset help option or ? option lockout prn unlockout prn unlockoutall log [port],datatype,[trigger],[period],[offset],{hold} unlog [port],data type unlogall [port] 227 J Listing Of Tables Table 2-2 GPSCard Command Summary (continued) MAGVAR MESSAGES POSAVE RESET RINEX RTCM16T SETNAV Set magnetic variation correction Disable error reporting from command interpreter Implements position averaging for reference station Performs a hardware reset (OEM only) Configure the user defined fields in the file headers Enter an ASCII text message to be sent out in the RTCM data stream Set variations of the RTCM bit rule Set up the RTK mode Save the latest almanac in non-volatile memory Save current configuration in non-volatile memory (OEM only) Send an ASCII message to any of the communications ports Sends non-printable characters in hexadecimal pairs Enter in a reference station ID Override PRN health Reset PRN health Reset all PRN health Add an offset to the L1 pseudorange to compensate for signal delays Set a destination waypoint SETTIMESYNC UNDULATION VERSION Enable or disable time synchronization Choose undulation Current software and hardware information RTCMRULE RTKMODE SAVEALMA SAVECONFIG SEND SENDHEX SETDGPSID SETHEALTH RESETHEALTH RESETHEALTHALL SETL1OFFSET 228 magvar value messages port,option posave maxtime, maxhorstd, maxverstd reset rinex cfgtype rtcm16t ascii message rtcmrule rule rrtkmode arguement, data range savealma option saveconfig send port ascii-message sendhex port data setdgpsid option sethealth prn,health resethealth prn resethealthall setL1offset distance setnav from lat,from lon,to lat, to lon,track offset, from port,to port settimesync flag undulation separation version MiLLennium Command Descriptions Manual J Listing Of Tables Table 4-1 Logs By Function Table COMMUNICATIONS, CONTROL AND STATUS Logs Descriptions CDSA/B COM port communications status COM1A/B COM2A/B Log data from COM1 Log data from COM2 COMnA/B Pass-through data logs RCSA/B RTCM16T Receiver self-test status NovAtel ASCII format special message RTCM16 RTCM format special message GENERAL RECEIVER CONTROL AND STATUS Logs Descriptions PVAA/B Receiver’s latest computed position, velocity and acceleration in ECEF coordinates RCCA Receiver configuration status RCSA/B RVSA/B Version and self-test status Receiver status VERA/B Receiver hardware and software version numbers POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL Logs Descriptions DOPA/B DOP of SVs currently tracking GGAB GPS fix data GPGGA GPGLL NMEA, position data NMEA, position data GPGRS GPGSA NMEA, range residuals NMEA, DOP information GPGST NMEA, measurement noise statistics MKPA/B Position at time of mark POSA/B Position data PRTKA/B PXYA/B Computed position Position (Cartesian x,y,z coordinates) RTKA/B RTKOA/B Computed position RTK Output SPHA/B Speed and direction over ground SATELLITE TRACKING AND CHANNEL CONTROL Logs Descriptions ALMA/B DOPA/B Current decoded almanac data DOP of SVs currently tracking ETSA/B Provides channel tracking status information for each of the GPSCard parallel channels GPALM NMEA, almanac data GPGSA NMEA, SV DOP information GPGSV RALA/B NMEA, satellite-in-view information Raw almanac RASA/B RGEA/B/D Raw GPS almanac set Satellite range measurements SATA/B SVDA/B Satellite specific information SV position (ECEF xyz) MiLLennium Command Descriptions Manual 229 J Listing Of Tables Table 4-1 Logs By Function Table (continued) Logs WAYPOINT NAVIGATION Descriptions GPRMB NMEA, waypoint status GPRMC NMEA, navigation information GPVTG GPZTG NMEA, track made good and speed NMEA, time to destination MKPA/B NAVA/B Position at time of mark input Navigation waypoint status POSA/B Position data SPHA/B Speed and course over ground VLHA/B Velocity, latency & direction over ground Logs DIFFERENTIAL REFERENCE STATION Descriptions ALMA/B Current almanac information CDSA/B PAVA/B COM port data transmission status Parameters being used in the position averaging process RGEA/B/D Channel range measurements RPSA/B Reference station position and health Transmits RTCA differential corrections in NovAtel ASCII or Binary RTCAA/B RTCM Transmits RTCM SC104 standard corrections RTCM3 Reference position RTCM59 NovAtel format RT-20 observation data RTCMA/B SATA/B Transmits RTCM information in NovAtel ASCII/binary Satellite specific information Logs DIFFERENTIAL REMOTE STATION Descriptions CDSA/B Communication and differential decode status GPGGA NMEA, position fix data GGAB POSA/B NovAtel binary version of GPGGA Position information PRTKA/B Computed Position – best available RTKA/B Computed Position – Time Matched SATA/B Satellite specific information SVDA/B VLHA/B SV position in ECEF XYZ with corrections Velocity, latency & direction over ground Logs POST PROCESSING DATA Descriptions BSLA/B Most recent matched baseline expressed in ecef coords CLKA/B REPA/B Receiver clock offset information Raw ephemeris information RGEA/B/D SATA/B Satellite and ranging information Satellite specific information SVDA/B SV position in ECEF XYZ with corrections CLOCK INFORMATION, STATUS, AND TIME Logs Descriptions CLKA/B Receiver clock offset information CLMA/B GPZDA Current clock-model matrices of the GPSCard NMEA, UTC time and date GPZTG MKTA/B NMEA, UTC and time to waypoint Time of mark input TM1A/B Time of 1PPS 230 MiLLennium Command Descriptions Manual J Listing Of Tables Table 4-2 GPSCard Log Summary Syntax: log port,datatype,[trigger],[period],[offset],{hold} NovAtel Format Logs Datatype ALMA/B BSLA/B CDSA/B Description Datatype Description Decoded Almanac Baseline Measurement Communication and Differential Decode Status Receiver Clock Offset Data Receiver Clock Model Log data from COM1 Log data from COM2 RALA/B RASA/B RCCA Raw Almanac Raw GPS Almanac Set Receiver Configuration REPA/B RGEA/B/D RPSA/B RTCAA/B RTKA/B RTKOA/B RTCMA/B MKPA/B MKTA/B NAVA/B PAVA/B POSA/B Dilution of Precision Extended Tracking Status Global Position System Fix Data - Binary Format Mark Position Time of Mark Input Navigation Data Positioning Averaging Status Computed Position PRTKA/B PVAA/B Computed Position XYZ Position, Velocity and Acceleration TM1A/B VERA/B PXYA/B Computed Cartesian Coordinate Position VLHA/B NMEA Format Logs Raw Ephemeris Channel Range Measurements Reference Station Position and Health RTCA format Differential Corrections with NovAtel headers Computed Position - Time Matched RTK Solution Parameters RTCM Type 1 Differential Corrections with NovAtel headers Special Message Receiver Status Satellite Specific Data Speed and Direction Over Ground SV Position in ECEF XYZ Coordinates with Corrections Time of 1PPS Receiver Hardware and Software Version Numbers Velocity, Latency, and Direction over Ground GPALM GPGGA GPGLL GPGRS GPGSA GPGST Almanac Data GPGSV Global Position System Fix Data GPRMB Geographic Position - lat/lon GPRMC GPS Range Residuals for Each Satellite GPVTG GPS DOP and Active Satellites GPZDA Pseudorange Measurement Noise GPZTG Statistics RTCA Format RTCA RTCA Differential Corrections: Type 1 and Type 7 RTCM Format RTCM RTCM3 RTCM9 RTCM16 RTCM59 Type 1 Differential GPS Corrections Type 3 Reference Station Parameters Type 9 Partial Satellite Set Differential Corrections Type 16 Special Message Type 59N-0 NovAtel Proprietary Message: RT20 Differential Observations CLKA/B CLMA COM1A/B COM2A/B DOPA/B ETSA/B GGAB N.B. A/B/D RTCM16T RVSA/B SATA/B SPHA/B SVDA/B GPS Satellites in View Generic Navigation Information GPS Specific Information Track Made Good and Ground Speed UTC Time and Date UTC & Time to Destination Waypoint A refers to GPSCard output logs in ASCII format. B refers to GPSCard output logs in Binary format. D refers to GPSCard output logs in Compressed binary format. MiLLennium Command Descriptions Manual 231 J Listing Of Tables Table 6-1 Positioning Modes Reference station: L1 RTCM Type 59N Reference station: L1 RTCA Type 7 Reference station: L1 & L2 RTCM Type 59N Reference station: L1 & L2 RTCA Type 7 Remote station: L1 RT-20 RT-20 RT-20 RT-20 Remote station: L1 & L2 RT-20 RT-20 RT-20 RT-2 Table C-1 Antenna LNA Power Configuration P301: plug connects pins 1&2 ANTENNAPOWER = ON ANTENNAPOWER = OFF internal power connected to LNA internal power cut off from LNA P301: plug connects pins 2&3 P301: no plug no external effect no external effect no external effect no external effect Table C-2 Default Values of Process Noise Elements h0 Timing Standard VCTCXO OCXO rubidium cesium user (min / max) h-1 1.0 e-21 2.51 e-26 1.0 e-23 2.0 e-20 1.0 e-31 ≤ h0 ≤ 1.0 e-18 1.0 e-20 2.51 e-23 1.0 e-22 7.0 e-23 1.0 e-31 ≤ h-1 ≤ 1.0 e-18 h-2 2.0 e-20 2.51 e-22 1.3 e-26 4.0 e-29 1.0 e-31 ≤ h-2 ≤ 1.0 e-18 Table C-3 VARF Range (Software Version 4.42 or higher) n 1 1024 1 1 2 1 232 k p 1 65 536 65 536 4000 4 2 1 65 536 65 536 5000 8 2 VARF (Hz) 0 0.004 652 065 0.004 656 612 1 312 500 5 000 000 (Minimum) (Maximum) MiLLennium Command Descriptions Manual J Listing Of Tables Table D-1 GPSCard Solution Status Value 0 1 2 3 Description Solution computed Insufficient observations No convergence Singular ATPA Matrix Covariance trace exceeds maximum (trace > 1000 m) Test distance exceeded (maximum of 3 rejections if distance > 10 km) Not yet converged from cold start Height or velocity limit exceeded. (In accordance with COCOM export licensing restrictions) 4 5 6 7 Higher numbers are reserved for future use Table D-2 Position Type Type 0 1 2 3 4 Definition No position Single point position Differential pseudorange position RT-20 position RT-2 position Higher numbers are reserved for future use Table D-3 RTK Status for Position Type 3 (RT-20) Status 0 1 2 3 4 5 6 7 8 Definition Floating ambiguity solution (converged) Floating ambiguity solution (not yet converged) Modelling reference phase Insufficient observations Variance exceeds limit Residuals too big Delta position too big Negative variance RTK position not computed Higher numbers are reserved for future use MiLLennium Command Descriptions Manual 233 J Listing Of Tables Table D-4 RTK Status for Position Type 4 (RT-2) Status Definition 0 1 2 3 4 5 6 7 8 9 10 Narrow lane solution Wide lane derived solution Floating ambiguity solution (converged) Floating ambiguity solution (not yet converged) Modelling reference phase Insufficient observations Variance exceeds limit Residuals too big Delta position too big Negative variance RTK position not computed Higher numbers are reserved for future use Table D-5 Receiver Self-Test Status Codes N7 N 6 27 26 25 N 5 24 23 22 21 N 4 20 N 3 19 18 17 16 15 14 13 12 11 N 2 10 9 N 1 8 7 6 5 N 0 4 3 2 1 0 <- <- Nibble Number B it Descriptio n lsb = 0 ANTENNA 1 L1 PLL Range Values Hex Value 1 =good, 0 =bad 00000001 1 =good, 0 =bad 00000002 2 RAM 1 =good, 0 =bad 00000004 3 ROM 1 =good, 0 =bad 00000008 4 DSP 1 =good, 0 =bad 00000010 5 L1 AGC 1 =good, 0 =bad 00000020 6 COM 1 1 =good, 0 =bad 00000040 7 COM 2 1 =good, 0 =bad 00000080 8 WEEK 1 =not set , 0 =set 00000100 9 NO COARSETIME 1 =not set , 0 =set 00000200 10 NO FINETIME 1 =not set , 0 =set 00000400 11 L1 JAMMER 1 =present , 0 =normal 00000800 12 BUFFER COM 1 1 =overrun, 0 =normal 00001000 13 BUFFER COM 2 1 =overrun, 0 =normal 00002000 14 BUFFER CONSOLE 1 =overrun, 0 =normal 00004000 15 CPU OVERLOAD 1 =overload, 0 =normal 00008000 16 ALMANAC SAVED IN NVM 1 =yes, 0 =no 00010000 17 L2 AGC 1 =good, 0 =bad 00020000 18 L2 JAMMER 1 =present , 0 =normal 00040000 19 L2 PLL 1 =good, 0 =bad 00080000 20 OCXO PLL 1 =good, 0 =bad 00100000 21 SAVED ALMA. NEEDS UPDATE 1 =yes, 0 =no 00200000 22 ALMANAC INVALID 1 =invalid, 0 =valid 00400000 23 POSITION SOLUTION INVALID 1 =invalid, 0 =valid 00800000 24 POSITION FIXED 1 =yes, 0 =no 01000000 25 CLOCK MODEL INVALID 1 =invalid, 0 =valid 02000000 26 CLOCK STEERING DISABLED 1 =disabled, 0 =enabled 04000000 27 RESERVED 28-31 RESERVED Notes on Table D-5: 1. Bit 3: On OEM GPSCards, “ROM” includes all forms of non-volatile memory. 2. Bits 12-15: Flag is reset to 0 five minutes after the last overrun/overload condition has occurred. 234 MiLLennium Command Descriptions Manual J Listing Of Tables Table D-6 Range Record Format (RGED only) Data PRN ① C/No ② Lock time ③ ADR ④ Doppler frequency Pseudorange StdDev - ADR StdDev - pseudorange ChannelTracking status ➅ Bit(s) from first to last Length (bits) 0..5 6..10 11.31 32..63 68..95 64..67 msn; 96..127 lsw 128..131 132..135 136..159 6 5 21 32 28 36 4 4 24 Format integer integer integer integer 2's comp. integer 2's comp. integer 2's comp. integer integer Scale Factor 1 (20+n) dB-Hz 1/32 s 1/256 cycles 1/256 Hz 1/128 m (n+1) / 512 cyc see ➄ see Table D-7 Notes on Table D-6: ① Only PRNs 1 - 63 are reported correctly (Note: while there are only 32 PRNs in the basic GPS scheme, situations exist which require the use of additional PRNs) ② C/No is constrained to a value between 20 - 51 dB-Hz. Thus, if it is reported that C/No = 20 dB-Hz, the actual value could be less. Likewise, if it is reported that C/No = 51 dB-Hz, the true value could be greater. ③ Lock time rolls over after 2,097,151 seconds. ④ ADR (Accumulated Doppler Range) is calculated as follows: ADR_ROLLS = [( -RGED_PSR / WAVELENGTH - RGED_ADR)] / MAX_VALUE IF (ADR_ROLLS ≤ -0.5) ADR_ROLLS = ADR_ROLLS - 0.5 ELSE ADR_ROLLS = ADR_ROLLS + 0.5 (At this point integerise ADR_ROLLS) CORRECTED_ADR = RGED_ADR + (MAX_VALUE * ADR_ROLLS) where: ADR has units of cycles WAVELENGTH = 0.1902936727984 for L1 WAVELENGTH = 0.2442102134246 for L2 MAX_VALUE = 8388608 ➄ Code RGED 0 0.000 to 0.050 1 0.051 to 0.075 2 0.076 to 0.113 3 0.114 to 0.169 4 0.170 to 0.253 5 0.254 to 0.380 6 0.381 to 0.570 7 0.571 to 0.854 8 0.855 to 1.281 9 1.282 to 2.375 10 2.376 to 4.750 11 4.751 to 9.500 12 9.501 to 19.000 13 19.001 to 38.000 14 38.001 to 76.000 15 76.001 to 152.000 ➅ Only bits 0 - 23 are represented in the RGED log MiLLennium Command Descriptions Manual 235 J Listing Of Tables Table D-7 Channel Tracking Status N 7 31 30 29 N 6 28 27 26 25 N 5 24 23 22 21 N 4 20 19 18 17 N 3 16 15 14 13 N 2 12 11 10 9 N 1 8 7 6 5 N 0 4 3 2 1 0 <- <- Nibble Number Bit Description Range Values lsb =0 Hex. 1 1 Tracking st at e 0 - 11 See below 2 2 4 3 8 4 10 5 0 - n (0 =f irst , n =last ) 20 6 Channel number (n depends on GPSCard) model) 40 1 =Lock, 0 =Not locked 200 7 8 80 100 9 Phase lock f lag 10 Parit y known f lag 1 =Known, 0 =Not known 400 11 Code locked f lag 1 =Lock, 0 =Not locked 800 0 - 7 See below 2000 12 1000 13 Correlat or spacing 14 4000 15 0=GPS 3=Pseudolit e GPS 8000 16 Sat ellit e syst em 1=GLONASS 4-7 Reserved 10000 17 2=WAAS 18 Reserved 20000 40000 19 Grouping 1 =Grouped, 0 =Not grouped 80000 20 Frequency 1 =L2, 0 =L1 100000 21 Code t ype 0 =C/ A 2 =P-codeless 200000 22 1 =P 3 =Reserved Foreword error 23 Forward errorconnection correct i 1 =FEC enabled, 0 =no FEC 400000 800000 24 : Reserved 29 30 Ext ernal range 1 =Ext . range, 0 =Int . range 31 Channel assignment 1 =Forced, 0 =Aut omat ic Table D-7 is referenced by the ETSA/B, and RGEA/B/D logs. Table D-7, Bits 0 - 3 : Channel Tracking State State 0 1 2 3 4 5 Description L1 Idle L1 Sky search L1 Wide frequency band pull-in L1 Narrow frequency band pull-in L1 Phase-lock loop L1 Re-acquisition State 6 7 8 9 10 11 Description L1 Steering L1 Frequency-lock loop L2 Idle L2 P-code alignment L2 Search L2 Phase-lock loop Higher numbers are reserved for future use Table D-7, Bits 12-14 : Correlator Spacing State 0 1 2 Description Unknown: this only appears in versions of software previous to x.4x, which didn’t use this field Standard correlator: spacing = 1 chip Narrow Correlator: spacing < 1 chip Higher numbers are reserved for future use 236 MiLLennium Command Descriptions Manual J Listing Of Tables Table D-8 Ambiguity Types Ambiguity Type Definition 0 L1 only floating 1 Wide lane fixed integer 2 Reserved 3 Narrow lane floating 4 Iono–free floating 5 Reserved 6 Narrow lane fixed integer 7 Iono–free fixed discrete 8 L1 only fixed integer 9 Reserved 10 Undefined type Higher numbers are reserved for future use Table D-9 Searcher Status Searcher Status Definition 0 No search requested 1 Searcher buffering measurements 2 Currently searching 3 Search decision made 4 Hand-off to L1 and L2 complete Higher numbers are reserved for future use Table D-10 RTK Status RTK Status Definition 1 Good narrowlane solution 2 Good widelane solution 4 Good L1/L2 converged float solution 8 Good L1/L2 unconverged float solution 16 Good L1 converged solution 32 Good L1 unconverged solution 64 Reserved for future use 128 Insufficient observations 256 Variance exceeds limit 512 Residuals exceed limit 1024 Delta position too large 2048 Negative variance 4096 Undefined 8192 RTK initialize MiLLennium Command Descriptions Manual 237 J Listing Of Tables Table D-11 GPSCard Range Reject Codes Value Description 0 Observations are good 1 Bad satellite health is indicated by ephemeris data 2 Old ephemeris due to data not being updated during last 3 hours 3 Eccentric anomaly error during computation of the satellite’s position 4 True anomaly error during computation of the satellite’s position 5 Satellite coordinate error during computation of the satellite’s position 6 Elevation error due to the satellite being below the cutoff angle 7 Misclosure too large due to excessive gap between estimated and actual positions 8 No differential correction is available for this particular satellite 9 Ephemeris data for this satellite has not yet been received 10 Invalid IODE due to mismatch between differential stations 11 Locked Out: satellite is excluded by user (LOCKOUT command) 12 Low Power: satellite rejected due to low signal/noise ratio 13 L2 measurements are not currently used in the filter Table D-12 GPSCard Velocity Status Value Description 0 ➂ Velocity computed from differentially corrected carrier phase data 1 ➂ Velocity computed from differentially corrected Doppler data 2 ➂ Old velocity from differentially corrected phase or Doppler (higher latency) 3 Velocity from single point computations 4 Old velocity from single point computations (higher latency) 5 Invalid velocity Table E-1 Comparison of RT-2 and RT-20 GPS Frequencies Utilized Nominal Accuracy Lane Searching RT-2 RT-20 L1 & L2 L1 2 cm (CEP) 20 cm (CEP) Wide lane and narrow lane None . Table E-2 RTK Messages Vs. Accuracy Transmitting (Reference) MiLLennium L1/L2 transmitting RTCA (i.e. RTCAOBS and RTCAREF) Receiving (Remote) MiLLennium L1/L2 receiver 100 metre 2DRMS MiLLennium RT-2 receiver 2 centimetre CEP GPSCard RT-20 receiver MiLLennium L1/L2 transmitting RTCM type 3 and 59 GPSCard RT-20 transmitting RTCM type 3 and 59 GPSCard RT-20 or MiLLennium L1/L2 transmitting RTCM or RTCA type 1 Accuracy Expected ➀ 20 centimetre CEP MiLLennium L1/L2 receiver 100 meter 2DRMS MiLLennium RT-2 receiver 20 centimetre CEP GPSCard RT-20 receiver 20 centimetre CEP MiLLennium L1/L2 receiver 100 meter 2DRMS MiLLennium RT-2 receiver 20 centimetre CEP GPSCard RT-20 receiver 20 centimetre CEP MiLLennium L1/L2 receiver 1 metre SEP MiLLennium RT-2 receiver 1 metre SEP GPSCard RT-20 receiver 1 metre SEP ➀ Not yet implemented in receiver firmware revision 3.34 238 MiLLennium Command Descriptions Manual J Listing Of Tables Table E-3 RT-2 Performance: Static Mode Baseline length < 10 km < 10 km < 15 km < 25 km < 35 km < 35 km Time since L2 lock-on with at least 6 satellites above mask angle Horizontal accuracy at the stated time 70 seconds + 1.5 sec/km 5 minutes 4 minutes 7 minutes 10 minutes 30 minutes 2 cm + 0.5 ppm 1 cm + 1 ppm 5 cm 7 cm 35 cm 25 cm Runs meeting the stated accuracy at the stated time 75.0% 75.0% 66.7% 66.7% 66.7% 66.7% Table E-4 RT-2 Performance: Kinematic Mode Baseline length < 10 km < 15 km < 25 km < 35 km < 35 km Time since L2 lock-on with at least 6 satellites above mask angle Horizontal accuracy at the stated time 120 seconds + 1.5 sec/km 8 minutes 14 minutes 20 minutes 60 minutes 2 cm + 0.5 ppm 8 cm 10 cm 40 cm 25 cm Runs meeting the stated accuracy at the stated time 75.0% 66.7% 66.7% 66.7% 66.7% Table E-5 RT-20 Performance Tracking Time (sec) Mode ① Data Delay (sec) Distance (km) Accuracy (CEP) 1 - 180 180 - 3000 > 3000 Static Static Static 0 0 0 1 1 1 100 to 25 cm 25 to 5 cm 5 cm or less 1 - 600 600 - 3000 > 3000 Kinematic Kinematic Kinematic Either Either Either Either Either Either Either Either 0 0 0 0-2 2-7 7 - 30 30 - 60 > 60 0 0 0 1 1 1 1 1 1 1 1 0 - 10 10 - 20 20 - 50 100 to 25 cm 25 to 5 cm 5 cm or less +1 cm/sec +2 cm/sec +5 cm/sec +7 cm/sec (single point) +0.5 cm/km +0.75 cm/km +1.0 cm/km ➁ ② ③ ① Mode = Static or Kinematic (during initial ambiguity resolution) ② The accuracy specifications refer to the PRTKA/B logs which include about 3 cm extrapolation error. RTKA/B logs are more accurate but have increased latency associated with them. ③ Between 30 and 60 seconds assumes pseudorange differential positioning. If Type 1 corrections have not been transmitted, the accuracy drops to single-point mode after 60 seconds. MiLLennium Command Descriptions Manual 239 K GPS Glossary of Terms K K GPS GLOSSARY OF TERMS GPS Glossary of Terms ASCII — A 7 bit wide serial code describing numbers, upper and lower case characters, special and non-printing characters. Address field — for sentences in the NMEA standard, the fixed length field following the beginning sentence delimiter "$" (HEX 24). For NMEA approved sentences, composed of a two character talker identifier and a three character sentence formatter. For proprietary sentences, composed of the character "P" (HEX 50) followed by a three character manufacturer identification code. Almanac — a set of orbit parameters that allows calculation of approximate GPS satellite positions and velocities. The almanac is used by a GPS receiver to determine satellite visibility and as an aid during acquisition of GPS satellite signals. Almanac data — a set of data which is downloaded from each satellite over the course of 12.5 minutes. It contains orbital parameter approximations for all satellites, GPS to universal time conversion parameters, and single-frequency ionospheric model parameters. Arrival alarm — an alarm signal issued by a voyage tracking unit which indicates arrival at or at a predetermined distance from a waypoint [see arrival circle]. Arrival circle — an artificial boundary placed around the destination waypoint of the present navigation leg, and entering of which will signal an arrival alarm. Arrival perpendicular — crossing of the line which is perpendicular to the course line and which passes through the destination waypoint. Attenuation — reduction of signal strength Azimuth — the horizontal direction of a celestial point from a terrestrial point, expressed as the angular distance from 000° (reference) clockwise through 360°. The reference point is generally True North, but may be Magnetic North, or Relative (ship's head). Bearing — the horizontal direction of one terrestrial point from anther terrestrial point, expressed as the angular distance from a reference direction, usually measured from 000° at the reference direction clockwise through 360°. The reference point may be True North, Magnetic North, or Relative (ship's head). Carrier — the steady transmitted RF signal whose amplitude, frequency, or phase may be modulated to carry information. Carrier Phase Ambiguity (or sometimes ambiguity for short) — the number of integer carrier phase cycles between the user and the satellite at the start of tracking. Carrier phase measurements — these are “accumulated delta range” measurements. They contain the instantaneous phase of the signal (modulo 1 cycle) plus some arbitrary number of integer cycles. Once the receiver is tracking the satellite, the integer number of cycles correctly accumulates the change in range seen by the receiver. When a “lock break” occurs, this accumulated value can jump an arbitrary integer number of cycles (this is called a cycle slip). CEP — circular error probable; the required radius of a circle so that 50% of a set of events occur inside the boundary. Checksum — by NMEA standard, a validity check performed on the data contained in the sentences, calculated by the talker, appended to the message, then recalculated by the listener for comparison to determine if the message was received correctly. Required for some sentences, optional for all others. Circular Error Probable (CEP) — the radius of a circle, centred at the user’s true location, that contains 50 percent of the individual position measurements made using a particular navigation system. 240 MiLLennium Command Descriptions Manual K GPS Glossary of Terms Coarse Acquisition (C/A) Code — a spread spectrum direct sequence code that is used primarily by commercial GPS receivers to determine the range to the transmitting GPS satellite. Uses a chip rate of 1.023 MHz. Communication protocol — a method established for message transfer between a talker and a listener which includes the message format and the sequence in which the messages are to be transferred. Also includes the signalling requirements such as bit rate, stop bits, parity, and bits per character. Control segment — the Master Control Station and the globally dispersed reference Stations used to manage the GPS satellites, determine their precise orbital parameters, and synchronize their clocks. Course — the horizontal direction in which a vessel is to be steered or is being steered; the direction of travel through the air or water. Expressed as angular distance from reference North (either true, magnetic, compass, or grid), usually 000° (north), clockwise through 360°. Strictly, the term applies to direction through the air or water, not the direction intended to be made good over the ground (see track). Differs from heading. Course Made Good (CMG) — the single resultant direction from a given point of departure to a subsequent position; the direction of the net movement from one point to the other. This often varies from the track caused by inaccuracies in steering, currents, cross-winds, etc. This term is often considered to be synonymous with Track Made Good, however, track made good is the more correct term. Course Over Ground (COG) — the actual path of a vessel with respect to the Earth (a misnomer in that courses are directions steered or intended to be steered through the water with respect to a reference meridian); this will not be a straight line if the vessel's heading yaws back and forth across the course. Cross Track Error (XTE) — the distance from the vessel’s present position to the closest point on a great circle line connecting the current waypoint coordinates. If a track offset has been specified in the GPSCard SETNAV command, the cross track error will be relative to the offset track great circle line. Cycle Slip — when the carrier phase measurement jumps by an arbitrary number of integer cycles. It is generally caused by a break in the signal tracking due to shading or some similar occurrence. Dead Reckoning (DR) — the process of determining a vessel’s approximate position by applying from its last known position a vector or a series of consecutive vectors representing the run that has since been made, using only the courses being steered, and the distance run as determined by log, engine rpm, or calculations from speed measurements. Destination — the immediate geographic point of interest to which a vessel is navigating. It may be the next waypoint along a route of waypoints or the final destination of a voyage. Differential GPS (DGPS) — a technique to improve GPS accuracy that uses pseudorange errors at a known location to improve the measurements made by other GPS receivers within the same general geographic area. Dilution of Precision (DOP) — a numerical value expressing the confidence factor of the position solution based on current satellite geometry. The lower the value, the greater the confidence in the solution. DOP can be expressed in the following forms. GDOP - all parameters are uncertain (latitude, longitude, height, clock offset) PDOP - 3D parameters are uncertain (latitude, longitude, height) HTDOP - 2D parameters and time are uncertain (latitude, longitude, time) HDOP - 2D parameters are uncertain (latitude, longitude) VDOP - height is uncertain TDOP - clock offset is uncertain Doppler — the change in frequency of sound, light or other wave caused by movement of its source relative to the observer. MiLLennium Command Descriptions Manual 241 K GPS Glossary of Terms Doppler aiding — a signal processing strategy, which uses a measured Doppler shift to help a receiver smoothly track the GPS signal, to allow more precise velocity and position measurement. Double-Difference — a position estimation mechanization which uses observations which are differenced between receiver channels and between the reference and remote receivers. Double-Difference Carrier Phase Ambiguity (or sometimes double difference ambiguity or ambiguity, for short) — carrier phase ambiguities which are differenced between receiver channels and between the reference and remote receivers. They are estimated when a double difference mechanism is used for carrier phase positioning. Earth-Centred-Earth-Fixed (ECEF) — a right-hand Cartesian coordinate system with its origin located at the centre of the Earth. The coordinate system used by GPS to describe three-dimensional location. ECEF — Earth-Centred-Earth-Fixed. This is a coordinate-ordinate system which has the X-coordinate in the earth's equatorial plane pointing to the Greenwich prime meridian, the Z-axis pointing to the north pole, and the Y-axis in the equatorial plane 90° from the X-axis with an orientation which forms a right-handed XYZ system. Ellipsoid — a smooth mathematical surface which represents the earth’s shape and very closely approximates the geoid. It is used as a reference surface for geodetic surveys, see the PRTKA/B log in Appendix D. Ellipsoidal Height — height above a defined ellipsoid approximating the surface of the earth. Ephemeris — a set of satellite orbit parameters that is used by a GPS receiver to calculate precise GPS satellite positions and velocities. The ephemeris is used in the determination of the navigation solution and is updated periodically by the satellite to maintain the accuracy of GPS receivers. Ephemeris Data — the data downlinked by a GPS satellite describing its own orbital position with time. Epoch — same as measurement time epoch. The local time at which a GPSCard takes a measurement. Field — a character or string of characters immediately preceded by a field delimiter. Fixed Ambiguity Estimates — carrier phase ambiguity estimates which are set to a given number and held constant. Usually they are set to integers or values derived from linear combinations of integers. Fixed Discrete Ambiguity Estimates — carrier phase ambiguities which are set to values which are members of a predetermined set of discrete possibilities, and then held constant. Fixed field — a field in which the number of characters is fixed. For data fields, such fields are shown in the sentence definitions with no decimal point. Other fields which fall into this category are the address field and the checksum field (if present). Fixed Integer Ambiguity Estimates — carrier phase ambiguities which are set to integer values and then held constant. Flash ROM — Programmable read-only memory. Floating Ambiguity Estimates — ambiguity estimates which are not held to a constant value, but are allowed to gradually converge to the correct solution. GDOP — Geometric Dilution of Precision - A numerical value expressing the confidence factor of the position solution based on current satellite geometry. Assumes that 3D position (latitude, longitude, height) and receiver clock offset (time) are variables in the solution. The lower the GDOP value, the greater the confidence in the solution. Geoid — the shape of the earth if it were considered as a sea level surface extended continuously through the continents. The geoid is an equipotential surface coincident with mean sea level to which at every point the plumb line (direction in which gravity acts) is perpendicular. The geoid, affected by local gravity disturbances, has an irregular shape. See the PRTKA/B log in Appendix D. Geodetic datum — the reference ellipsoid surface that defines the coordinate system. 242 MiLLennium Command Descriptions Manual K GPS Glossary of Terms Geostationary — a satellite orbit along the equator that results in a constant fixed position over a particular reference point on the earth’s surface. (GPS satellites are not geostationary.) Global Positioning System (GPS) — full name NAVSTAR Global Positioning System, a space-based radio positioning system which provides suitably equipped users with accurate position, velocity and time data. When fully operational, GPS will provide this data free of direct user charge worldwide, continuously, and under all weather conditions. The GPS constellation will consist of 24 orbiting satellites, four equally spaced around each of six different orbiter planes. The system is being developed by the Department of Defence under U.S. Air Force management. Great circle — the shortest distance between any two points along the surface of a sphere or ellipsoid, and therefore the shortest navigation distance between any two points on the Earth. Also called Geodesic Line. HDOP — Horizontal Dilution of Precision - A numerical value expressing the confidence factor of the horizontal position solution based on current satellite geometry. Makes no constraint assumptions about time, and about height only if the FIX HEIGHT command has been invoked. The lower the HDOP value, the greater the confidence in the solution. HTDOP — Horizontal position and Time Dilution of Precision - A numerical value expressing the confidence factor of the position solution based on current satellite geometry. Assumes height is known if the FIX HEIGHT command has been invoked. If not, it will give the normalized precision of the horizontal and time parameters given that nothing has been constrained. The lower the HTDOP value, the greater the confidence factor. Heading — the direction in which a vessel points or heads at any instant, expressed in degrees 000° clockwise through 360° and may be referenced to True North, Magnetic North, or Grid North. The heading of a vessel is also called the ship's head. Heading is a constantly changing value as the vessel oscillates or yaws across the course due to the effects of the air or sea, cross currents, and steering errors. Integer Ambiguity Estimates — carrier phase ambiguity estimates which are only allowed to take on integer values. Iono-free Carrier Phase Observation — a linear combination of L1 and L2 carrier phase measurements which provides an estimate of the carrier phase observation on one frequency with the effects of the ionosphere removed. It provides a different ambiguity value (non-integer) than a simple measurement on that frequency. Kinematic — the user’s GPS antenna is moving. In GPS, this term is typically used with precise carrier phase positioning, and the term dynamic is used with pseudorange positioning. L1 frequency — the 1575.42 MHz GPS carrier frequency which contains the course acquisition (C/A) code, as well as encrypted P-code, and navigation messages used by commercial GPS receivers. L2 frequency — a secondary GPS carrier, containing only encrypted P-code, used primarily to calculate signal delays caused by the ionosphere. The L2 frequency is 1227.60 MHz. Lane — a particular discrete ambiguity value on one carrier phase range measurement or double difference carrier phase observation. The type of measurement is not specified (L1, L2, L1-L2, iono-free) Local Observation Set — an observation set, as described below, taken by the receiver on which the software is operating as opposed to an observation taken at another receiver (the reference station) and transmitted through a radio link. Local Tangent Plane — a coordinate system based on a plane tangent to the ellipsoid’s surface at the user’s location. The three coordinates are east, north and up. Latitude, longitude and height positions operate in this coordinate system. Low-latency Solution — a position solution which is based on a prediction. A model (based on previous reference station observations) is used to estimate what the observations will be at a given time epoch. These estimated reference station observations are combined with actual measurements taken at the remote station to provide a position solution. Magnetic bearing — bearing relative to magnetic north; compass bearing corrected for deviation. MiLLennium Command Descriptions Manual 243 K GPS Glossary of Terms Magnetic heading — heading relative to magnetic north. Magnetic variation — the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. Mask angle — the minimum GPS satellite elevation angle permitted by a particular receiver design. Satellites below this angle will not be used in position solution. Matched Observation Set Pair — it contains observations from both the reference station and the local receiver which have been matched by time epoch, contain the same satellites, and are corrected for any known offsets. Measurement error variance — the square of the standard deviation of a measurement quantity. The standard deviation is representative of the error typically expected in a measured value of that quantity. Measurement Time Epoch — the local time at which a GPSCard takes a measurement. Multipath errors — GPS positioning errors caused by the interaction of the GPS satellite signal and its reflections. Nanosecond — 1 × 10-9 second Nautical mile — any of various units of distance for sea and air navigation; in the U.S. since 1959, an international unit of linear measure equal to 1 minute of arc of a great circle of the Earth, 1,852 metres (6,076 feet). Non-Volatile Memory — a type of memory device that retains data in the absence of a power supply. Null field — by NMEA standard, indicates that data is not available for the field. Indicated by two ASCII commas, i.e., ",," (HEX 2C2C), or, for the last data field in a sentence, one comma followed by either the checksum delimiter "*" (HEX 2A) or the sentence delimiters (HEX 0D0A). [Note: the ASCII Null character (HEX 00) is not to be used for null fields.] Obscuration — term used to describe periods of time when a GPS receiver’s line-of-sight to GPS satellites is blocked by natural or man-made objects. Observation — an input to an estimation algorithm. The two observations used in NovAtel’s RTK algorithms are the pseudorange measurement and the carrier phase measurement. Observation Set — a set of GPSCard measurements taken at a given time which includes one time for all measurements, and the following for each satellite tracked: PRN number, pseudorange or carrier phase or both, lock time count, signal strength, and tracking status. Either L1 only or L1 and L2 measurements are included in the set. The observation set is assumed to contain information indicating how many satellites it contains and which ones have L1-only and which ones have L1/L2 pairs. Origin waypoint — the starting point of the present navigation leg, expressed in latitude and longitude. Parallel receiver — a receiver that monitors four or more satellites simultaneously with independent channels. P-Code (precise or protected) — a spread spectrum direct sequence code that is used primarily by military GPS receivers to determine the range to the transmitting GPS satellite. Uses a chipping rate of 10.23 MHz. PDOP — Position Dilution of Precision. This is related to GDOP. It describes the effects of geometry on 3 dimensional positioning accuracy. It is defined to be the square root of the sum of the three diagonals of a normalized (assume measurement noise = 1) covariance matrix which correspond to position error. Precise Positioning Service (PPS) — the GPS positioning, velocity, and time service which will be available on a continuous, worldwide basis to users authorized by the U.S. Department of Defence (typically using P-Code). 244 MiLLennium Command Descriptions Manual K GPS Glossary of Terms PRN number — a number assigned by the GPS system designers to a given set of pseudorandom codes. Typically, a particular satellite will keep its PRN (and hence its code assignment) indefinitely, or at least for a long period of time. It is commonly used as a way to label a particular satellite. Pseudolite — an Earth-based transmitter designed to mimic a satellite. May be used to transmit differential corrections. Pseudorange — the calculated range from the GPS receiver to the satellite determined by taking the difference between the measured satellite transmit time and the receiver time of measurement, and multiplying by the speed of light. This measurement generally contains a large receiver clock offset error. Pseudorange Measurements — measurements made using one of the pseudorandom codes on the GPS signals. They provide an unambiguous measure of the range to the satellite including the effect of the satellite and user clock biases. Receiver channels — a GPS receiver specification which indicates the number of independent hardware signal processing channels included in the receiver design. Reference Satellite — in a double difference implementation, measurements are differenced between different satellites on one receiver in order to cancel the clock bias effect. Usually one satellite is chosen as the “reference”, and all others are differenced with it. Reference Station — the GPS receiver which is acting as the stationary reference. It has a known position and transmits messages for the "remote" receiver to use to calculate its position. Relative bearing — bearing relative to heading or to the vessel. Remote Receiver — the GPS receiver which does not know its position and needs to receive measurements from a reference station to calculate differential GPS positions. (The terms remote and rover are interchangeable.) Residual — in the context of measurement, the residual is the misclosure between the calculated measurements, using the position solution and actual measurements. RMS — root-mean-square, a probability level of 66%. Route — a planned course of travel, usually composed of more than one navigation leg. Rover Receiver — the GPS receiver which does not know its position and needs to receive measurements from a reference station to calculate differential GPS positions. (The terms rover and remote are interchangeable.) RT-20 — NovAtel’s Double Differencing Technology for real-time kinematic (RTK) carrier phase floating ambiguity resolution. RTCA — Radio Technical Commission for Aeronautics, an organization which developed and defined a message format for differential positioning. See Appendix F for further information. RTCM — Radio Technical Commission for Maritime Services, an organization which developed and defined the SC-104 message format for differential positioning. See Appendix F for further information. RTK — real-time kinematic, a type of differential positioning based on observations of carrier phase. In this document it is also used with reference to RT-2 and RT-20. Satellite elevation — the angle of the satellite above the horizon. Selected waypoint — the waypoint currently selected to be the point toward which the vessel is travelling. Also called "to" waypoint, destination or destination waypoint. Selective Availability (SA) — the method used by the United States Department of Defence to control access to the full accuracy achievable by civilian GPS equipment (generally by introducing timing and ephemeris errors). Sequential receiver — a GPS receiver in which the number of satellite signals to be tracked exceeds the number of available hardware channels. Sequential receivers periodically reassign hardware channels to particular satellite signals in a predetermined sequence. MiLLennium Command Descriptions Manual 245 K GPS Glossary of Terms Spherical Error Probable (SEP) — the radius of a sphere, centred at the user’s true location, that contains 50 percent of the individual three-dimensional position measurements made using a particular navigation system. Spheroid — sometimes known as ellipsoid; a perfect mathematical figure which very closely approximates the geoid. Used as a surface of reference for geodetic surveys. The geoid, affected by local gravity disturbances, is irregular. Standard Positioning Service (SPS) — a positioning service made available by the United States Department of Defence which will be available to all GPS civilian users on a continuous, worldwide basis (typically using C/A Code). SV — Space Vehicle ID, sometimes used as SVID; also used interchangeably with Pseudo-Random Noise Number (PRN). SEP — spherical error probable; the required radius of a sphere so that 50% of a set of events occur inside the boundary. Static — the user’s GPS antenna does not move. TDOP — Time Dilution of Precision - A numerical value expressing the confidence factor of the position solution based on current satellite geometry. The lower the TDOP value, the greater the confidence factor. Three-dimensional coverage (hours) — the number of hours-per-day when four or more satellites are available with acceptable positioning geometry. Four visible satellites are required to determine location and altitude. Three-dimensional (3D) navigation — navigation mode in which altitude and horizontal position are determined from satellite range measurements. Time-To-First-Fix (TTFF) — the actual time required by a GPS receiver to achieve a position solution. This specification will vary with the operating state of the receiver, the length of time since the last position fix, the location of the last fix, and the specific receiver design. Track — a planned or intended horizontal path of travel with respect to the Earth rather than the air or water. The track is expressed in degrees from 000° clockwise through 360° (true, magnetic, or grid). Track made good — the single resultant direction from a point of departure to a point of arrival or subsequent position at any given time; may be considered synonymous with Course Made Good. True bearing — bearing relative to true north; compass bearing corrected for compass error. True heading — heading relative to true north. Two-dimensional coverage (hours) — the number of hours-per-day with three or more satellites visible. Three visible satellites can be used to determine location if the GPS receiver is designed to accept an external altitude input. Two-dimensional (2D) navigation — navigation mode in which a fixed value of altitude is used for one or more position calculations while horizontal (2D) position can vary freely based on satellite range measurements. Undulation — the distance of the geoid above (positive) or below (negative) the mathematical reference ellipsoid (spheroid). Also known as geoidal separation, geoidal undulation, geoidal height. Universal Time Coordinated (UTC) — this time system uses the second-defined true angular rotation of the Earth measured as if the Earth rotated about its Conventional Terrestrial Pole. However, UTC is adjusted only in increments of one second. The time zone of UTC is that of Greenwich Mean Time (GMT). Update rate — the GPS receiver specification which indicates the solution rate provided by the receiver when operating normally. 246 MiLLennium Command Descriptions Manual K GPS Glossary of Terms VDOP — Vertical Dilution of Precision. This is related to GDOP. It describes the effects of geometry on vertical positioning accuracy. It is defined to be the square root of the diagonal of a normalized (assume measurement noise = 1) covariance matrix which corresponds to vertical position error. Variable field — by NMEA standards, a data field which may or may not contain a decimal point and which may vary in precision following the decimal point depending on the requirements and the accuracy of the measuring device. WGS84 — World Geodetic System 1984 is an ellipsoid designed to fit the shape of the entire Earth as well as possible with a single ellipsoid. It is often used as a reference on a worldwide basis, while other ellipsoids are used locally to provide a better fit to the Earth in a local region. GPS uses the centre of the WGS84 ellipsoid as the centre of the GPS ECEF reference frame. Waypoint — a reference point on a track. Wide Lane — a particular integer ambiguity value on one carrier phase range measurement or double difference carrier phase observation when the difference of the L1 and L2 measurements is used. It is a carrier phase observable formed by subtracting L2 from L1 carrier phase data: Φ' = Φ1 - Φ2. The corresponding wavelength is 86.2 cm MiLLennium Command Descriptions Manual 247 L GPS Glossary of Acronyms L GPS GLOSSARY OF ACRONYMS L GPS GLOSSARY OF ACRONYMS 1PPS 2D 3D One Pulse Per Second Two Dimensional Three Dimensional A/D ADR AGC ASCII Analog-to-Digital Accumulated Doppler Range Automatic Gain Control American Standard Code for Information Interchange BIH BIST bps Bureau l’International de l’Heure Built-In-Self-Test Bits per Second C/A Code CEP CPU CR CRC CTP CTS CTS Coarse/Acquisition Code Circular Error Probable Central Processing Unit Carriage Return Cyclic Redundancy Check Conventional Terrestrial Pole Conventional Terrestrial System Clear To Send dB DCE DGNSS DGPS DOP DSP DSR DTR Decibel Data Communications Equipment Differential Global Navigation Satellite System Differential Global Positioning System Dilution Of Precision Digital Signal Processor Data Set Ready Data Terminal Ready ECEF ESD Earth-Centred-Earth-Fixed Electrostatic Discharge FEC Forward Error Correction GDOP GMT GND GPS Geometric Dilution Of Precision Greenwich Mean Time Ground Global Positioning System HDOP hex HTDOP Hz Horizontal Dilution Of Precision Hexadecimal Horizontal position and Time Dilution Of Precision Hertz IC IF I/O IODE IRQ Integrated Circuit Intermediate Frequency Input/Output Issue of Data (Ephemeris) Interrupt Request LF LHCP LNA LO lsb Line Feed Left Hand Circular Polarization Low Noise Amplifier Local Oscillator Least significant bit MET Multipath Elimination Technology 248 MiLLennium Command Descriptions Manual L GPS Glossary of Acronyms MEDLL MKI MKO msb msec MSL Multipath Estimation Delay Lock Loop Mark In Mark Out Most significant bit millisecond Mean sea level N. mi. NAVSTAR NCO NMEA ns Nautical mile NAVigation Satellite Timing And Ranging (synonymous with GPS) Numerically Controlled Oscillator National Marine Electronics Association nanosecond OCXO OEM Oven Controlled Crystal Oscillator Original Equipment Manufacturer PC P Code PDOP PLL PPS PRN Personal Computer Precise Code Position Dilution Of Precision Phase Lock Loop Precise Positioning Service or Pulse Per Second PseudoRandom Noise number RAM RF RHCP ROM RTCA RTCM RTK RTS RXD Random Access Memory Radio Frequency Right Hand Circular Polarization Read Only Memory Radio Technical Commission for Aviation Services Radio Technical Commission for Maritime Services Real Time Kinematic Request To Send Received Data SA SCAT-I SEP SNR SPS SV SVN Selective Availability Special Category I Spherical Error Probable Signal-to-Noise Ratio Standard Positioning Service Space Vehicle Space Vehicle Number TCXO TDOP TTFF TXD Temperature Compensated Crystal Oscillator Time Dilution Of Precision Time-To-First-Fix Transmitted Data UART UDRE UTC Universal Asynchronous Receiver Transmitter User Differential Range Error Universal Time Coordinated VARF VDOP Variable Frequency Vertical Dilution of Precision WGS wpt World Geodetic System Waypoint XTE Crosstrack Error MiLLennium Command Descriptions Manual 249 NovAtel Inc. 1120 - 68 Avenue NE Calgary, Alberta, Canada, T2E 8S5 GPS Hotline: (403) 295-4900 GPS Fax: (403) 295-4901 E-mail: support@novatel.ca Web site: http://www.novatel.ca OM-20000026 Rev 1 Recyclable Printed in Canada on recycled paper 97/10/28
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