Novatel OM-20000026 User Manual

Software Version 4.45 OM-20000026 Rev 1

MiLLennium

GPSCard

Command Descriptions Manual

GPSCard™ Products NovAtel Inc.

TABLE OF CONTENTS

1Quick 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

2Command Descriptions

2.1 General .................. . ............................................................ ....................................................................................10

2.2 Command Tables ................................................................................ ....................................................................11

All Commands: ..............................................................................................................................................16

3Special 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

4Data 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

5Special Pass-Through Logs

5.1 Command Syntax .............. ................. .................. ................. .................................................................................31

5.2 ASCII Log Structure .................... ....................... . ..................... .. ....................... ....................................................32

5.3 Binary Log Structure...............................................................................................................................................33

6Message 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

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MiLLennium Command Descriptions Manual iii

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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 .................. ... ... ... ... . ... ... ... ... ... ... ..... .. ... ... ... ... ... ... ... . ... ... ... ..... ... ... ... .. ... ... ... ... ................................7 1

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

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

DLogs 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

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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.................................................. .................. ................. ................................... ...................................1 86

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

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Table of Contents

FIGURES

5-1 Pass-Through Log Data ................................................................................................................................................... 31

A-1 NAVSTAR Satellite Orbit Arrangement .........................................................................................................................50

A-2 Illustration of GPSCard Height Measurements ................................................................................................................52

A-3 Accuracy vs. Precision ..................................................................................................................................................... 53

A-4 Example of Differential Positioning ................................................................................................................................54

A-5 Single Point Averaging ....................................................................................................................................................57

A-6 Typical Differential Configuration ................................................................................................................................... 58

B-1 Illustration of GPS Signal Multipath ........................................................................................................ ........................61

B-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height ............................................................................... 63

B-3 Illustration of Quadrifilar vs. Microstri p Patch Antennae ................................................................................................64

B-4 Example of GPSAntenna on a Flat Plate vs. Choke Ring Ground Plane ......................................................................... 64

C-1 HELP Command Screen Display ..................................................................................................................................... 89

C-2 Appended Command Screen Display ............................................................................................................................... 89

C-3 Illustration of Magnetic Variation & Correction .............................................................................................................. 92

C-4 Using SEND Command ................................................................................................................................................... 106

C-5 Illustration of SETNAV Parameters ................................................................................................................................. 112

C-6 Illustration of Undulation ................................................................................................................................................. 115

D-1 Example of Navigation Parameters .................................................................................................................................. 158

D-2 The WGS84 ECEF Coordinate System ........................................................................................................................... 168

E-1 Typical RT-2 Horizontal Convergence - Static Mode ...................................................................................................... 208

E-2 Typical RT-2 Horizontal Convergence - Kinematic Mode .............................................................................................. 208

E-3 RT-2 Accuracy Convergence ...........................................................................................................................................209

E-4 Illustration of RT-2 St eady State Performance ................................. ............................................ ....................................209

E-5 Typical RT-20 Convergenc e - S tatic Mode ........................ ................................... ........................ ................................... 210

E-6 Typical RT-20 Convergence - Kinematic Mode ..............................................................................................................211

E-7 RT-20 Steady State Performance ......................................................... ............................................................................. 211

E-8 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 Configuratio n .................................................................................................................................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 Ambiguit y Type s .............................................................................................................................................................. 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

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 integrat ion and configuration. You a re free to select an appropriate data and signal interface, power supply system and mou ntin g struct ure. 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 no w 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 term inal or an IBM-com pati ble 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 MiL Lennium GPSCard resides in its read-only memory. As such, the unit “self-boots” upon power-up. The green LED indicator s hould blink about once per seco nd if the u nit is operating normally. T he r ed one ligh ts up if an error is detected during a self-test. The self-test statu s wo rd can be viewed in the

If a persistent error develops please contact the NovAtel GPS Customer Service Depar tment for further assistance

COMMUNICATION DEFAULT SETTINGS

COM1 and COM2 for the MiLLennium GPSCards are defaulted to the following RS232 protocol:

RGEA/B/D and RVSA/B data output logs.

• 9600 bps, no parity, 8 data bits, 1stop bit, no handshake, echo off

Graphical In te r fa c e

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 with out 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 o pen those you wish to display . To sen d commands and log data the Command C onsole screen should be visible. ASCII format logs can be monitored on the ASCII Record screen.

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1 Quick Start

e.g. On the command line of the Command Console screen type:log com1 posa once After you hit the <Enter> key the ASCII Record screen will display the outpu t for your current position . See the

POSA/B log description in Appendix D.

1.2 DATA LOGGING

The GPSCard has four major l ogg ing 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 command. The LOG command and syntax are listed on the following page.

LOG

Syntax:

Syntax Description Example

LOG LOG port COM1 or COM2 Defaults to the port that the command was entered on. COM1 datatype Enter one of the valid ASCII or Binary Data Logs (see Chapter 4 and Appendix D) POSA trigger Enter one of the following triggers. ONTIME

period Use only with the

offset Use only with the

hold Will prevent a log from being removed when the UNLOGALL command is issued HOLD

log [port],datatype,[trigger],[period],[offset],{hold}

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

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

[period], [offset]

CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer

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.

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).

at time of mark - does not extrapolate to mark time. Use MKBA/B for extrapolated position at time of mark.

Immediately logs the selected data and then periodically logs the selected data at a 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).

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.

ONTIME

trigger. Units for this parameter are seconds. The selected period may be any value

trigger. Units for this parameter are seconds. It provides the ability to offset the

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

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Example:

log com1,posa,ontime,60,1

If the

LOG syntax does not include a trigger type, it will be out put only once following execution of the LOG

command. If trigger type is specified in the LOG syntax, the log will continue to be output bas ed on the trigger specification. Specific logs can be disabled using the by using the configuration status log (

UNLOGALL command (see Chapter 2 and Appendix C). All activated logs will be listed in the receiver

RCCA).

UNLOG command, whereas all enabled logs will be disabled

The [port] parameter is optional. If [port] is not specified, [port] is defaulted to the p ort that the command was received on.

COMMONLY USED LOGS

Type Logs Trigger

Positioning PRTKA/B

POSA/B

Post Processing RGEA/B/D

REPA/B, ALMA/B

NMEA Position GPGLL

GPGGA

Other useful logs are

ontime or onmark

ontime onchanged

ontime or onmark

• 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 alpha betically 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

For detailed data structure concerning these logs, please see Chapters 4, 5, 6 and Appendix D.

Establish a Da ta Link

Operating the GPSCard with a DGPS system requires that the reference station b roadcast 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.

RTCM and RTCA.

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 li nk and remote users. Us e the GPSCard COMn c ommand 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 t ime d with log transmissions.

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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 STATION REMO TE ST ATION

MONITOR STATION REMOTE STATION

equired: Required:

Required: Required:

FIX POSITION lat lon h g t id (h e a lth ) ACCEPT port

LOG port

DATATYPE

ecommended Options: Recommended Options:

Recommended Options: Recommended Options:

LOG DATATYPES

DATATYPE

(binary):

ontime 5

RTCMB

RTCAB

RTCM

RTCA

ACCEPT DATATYPES

DATATYPE

(binary):

RTCM RTCA

(ascii):

LOG DATATYPES

elated Commands /Logs: Related Commands /Logs:

Related Commands /Logs: Related Commands /Logs:

RTCMRULE RTCMRULE

DATUM DATUM

xample 1:

Example 1:

xample 2:

Example 2:

OTES: Italicized entries indicate user definable.

NOTES: Italicized entries indicate user definable.

fix position 51.3455323 -114.2895345 1201.123 555 0

log com1 RTCM ontime 2

fix position 51.3455323 -114.2895345 1201.123 555

log com2 rtcaa ontime 2

(ascii):

RTCMA

RTCAA

Example 1:

Example 2:

ACCEPT COMMANDS

POSA/B

VLHA/B

CDSA/B

GPGGA

accept com 2 rtcm

log com1 posa ontime 1

accept com2 commands

log com1 posa ontime 0.2

log com1 vlha ontime 0.2

(ascii):

RTCMA RTCAA

Initialization - Re ference Station

Differential mode of operation is established at the ref erence station through a two ste p 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

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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 trackin g 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 commu nications 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 1 cm/sec 2-7 seconds 2 cm/sec 7-30 seconds 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 additio nal 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:

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1 Quick Start

• 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.

2. RT-20 requires that the reference station periodically transmit either the RTCA messag es 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 stati on, and are ready to go. There are options, however, which can be used to adapt the system to a specific application. S ome options a pply only to the reference st ation, while oth e rs 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 more information.

• When using the sea level; it will be converted to ellipsoidal height inside the receiver. You can enter an undulation value, if desired, using 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.

FIX POSITION command, the height entered must be in metres above mean

RTKMODE commands in Chapter 2 and Appendix C for

UNDULATION command; if none is entered, the

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 com

Example:

fix position 51.11358042,-114.04358013,1059.4105,”RW34”

,rtcaobs,ontime,interval

6 MiLLennium Command Descriptions Manual

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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 RTC A or RTCM-format messaging, the use of RT CA-format messages is recommended (see Chapter 6 for further information on this topic). Nev ertheless, the follow ing 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, log comn,rtcm3,ontime,interval

station id,station health

log com

Example:

fix position 51.11358042,-114.04358013,1059.4105,119,0 log com1,rtcm3,ontime,10 log com1,rtcm59,ontime,2

,rtcm59,ontime,interval

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 t he low-latency position; the RTKA/B logs contai n t he 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 Loggi ng 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

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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 ephem delay

Command Option Description Default

DGPSTIMEOUT Command dgps delay min. 2

max. 1000

ephem delay min. 0

max. 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

To facilitate transmitting the

RTCM data over shared data links, the GPSCard is also capable of sending the RTCM

RTCM data.

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 CO M2 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 hexadecim al data to binary before the R TCM 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 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.

8 MiLLennium Command Descriptions Manual

RTCA type messages for transmitting and receiving differential corrections versus

RTCA is transmitted in 8-bit words, which are easier

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 input to that port. The

RTCA logs cannot be intermixed with other logs.

RTCA data

The RTCAA log can be intermixed with other NovAtel ASCII data over a common communicat ions 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 conv ert the hexadecimal data to binary before the RTCA Standard can be retrieved.

The RTCAB log can be intermixed with other NovAtel binary data. The C OM1 or COM2 port of the remote GPSCard must be dedicated to receiving issued. The remote GPSCard identifies the and will interpret only the

RTCA data portion of the log.

RTCA data only, and so the “ACCEPT port RTCA” command must be

RTCAB log by the message block identifier contain ed in the message,

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 ini tialize t he rover receiv e r to accept o bservation dat a from th e referen ce st ation. If th e receiv e r 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 properl y set up. As well, ensure that the COM port which is to receive the differential data is s et up to match the bit rate an d 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 G PSCard will revert to single point positioning until the pseu dorange 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 velocity data can be found in the

PRTKA/B logs to be the most informative. Oth er options exist, such as POSA/B and GPGGA. As well,

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.

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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 Chapter 4.

The GPSCard is capable of responding to over 50 differ ent input co mmands. You will fi nd t hat once you be c o me familiar with these commands, the GPSCard offers a wide range in operational flexibility. All com mands 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:

LOG command, see

• The commands are not case sensitive (

e.g. e.g.

HELP or help FIX POSITION or fix position

COMMAND or command).

• 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 <CR> key. A carriage return is what

the card is looking for and is usually the same as pressing the <Enter> 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>).

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

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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 Power to the low-noise amplifier of an active antenna COMn COMn port configuration control COMn_DTR DTR handshaking control COMn_RTS RTS handshaking control DIFF_PROTOCOL ➀ Differential Protocol Control FREQUENCY_OUT Variable frequency output (programmable) LOG Logging control MESSAGES Disable error reporting from command interpreter RINEX Configure the user defined fields in the file header RTCMRULE Sets up RTCM bit rule RTCM16T Enters an ASCII message SEND Sends ASCII message to COM port SENDHEX Sends non-printable characters

SETL1OFFSET ➀

Add an offset to the L1 pseudorange to compensate for signa l delays

GENERAL RECEIVER CONTROL AND STATUS

Commands Descriptions

$ALMA Download almanac data file CRESET R eset receiver to factory default DYNAMICS Set correlator tracking bandwidth HELP 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 Injects receiver time of 1 PPS VERSION Software/hardware information

POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL

Commands Descriptions

CSMOOTH 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 Constrains to fixed lat, lon, height FRESET Clears all data which is stored in NVM $IONA Download ionospheric correction data LOCKOUT Deweights a sate llite in solutions $PVAA ➀ Position, velocity and acceleration in ECEF coordinates RTKMODE Setup the RTK mode UNDULATION Ellipsoid-geoid separation USERDATUM User-customized datum

➀ Intended for advanced users of GPS only.

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2 Command Descriptions

Table 2-1 Commands By Function Table (continued)

SATELLITE TRACKING AND CHANNEL CONTROL

Commands Descriptions

$ALMA Download almanac data file ASSIGN Satellite channel assignment CONFIG Switches the channel configuration of the GPSCard DYNAMICS Sets correlator tracking bandwidth FIX VELOCITY Aids high velocity reacquisition RESETHEALTH R eset PRN health SETHEALTH Overrides broadcast satellite health

WAYPOINT NAVIGATION

Commands Descriptions

MAGVAR Magne tic variation co rrection SETNAV Waypoint input

DIFFERENTIAL REFERENCE STATION

Commands Descriptions

DGPSTIMEOUT Sets ephemeris delay FIX POSITION Constrain to fixed (reference) LOG Selects required di fferential-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 Input almanac data DGPSTIMEOUT Set maximum age of differential data accepted RESET Performs a hardware reset $RTCA RTCA differential correction input (ASCII) $RTCM RTCM differential correction in put (ASCII) RTCMRULE Selects RTCM bit rule SETDGPSID Select differential reference station ID to receive

POST PROCESSING DATA

Commands Descriptions

Depends on operating platform

CLOCK INFORMATION, STATUS, AND TIME

Commands Descriptions

CLOCKADJUST Enable clock modelling & 1PPS adjust DIFF_PROTOCOL ➀ Differential protocol control EXTERNALCLOCK Sets default parameters of an optional external oscillator EXTERNALCLOCK FREQUENCY Sets clock rate SETTIMESYNC ➀ Enable or disable time synchronization $UTCA Download UTC data

➀ Intended for advanced users of GPS only

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2 Command Descriptions

Table 2-2 GPSCard Command Summary

Command Description Syntax

$ALMA Injects almanac (follows NovAtel ASCII log format) $IONA Injects ionospheric refraction corrections (follows NovAtel ASCII log format) $PVAA Injects latest computed position, velocity and acceleration (follows NovAtel ASCII log format) $REPA Injects raw GPS ephemeris data (follows NovAtel ASCII log format) $RTCA Injects RTCA format DGPS corrections in ASCII (Type 1) (follows NovAtel ASCII log format) $RTCM Injects RTCM format differential corrections in ASCII (Type 1) (follows NovAtel ASCII log format) $TM1A Injects receiver time of 1 PPS (follows NovAtel ASCII log format) $UTCA Injects UTC information (follows NovAtel ASCII log format) ACCEPT Port input control (set command interpreter) accept port,option ANTENNAPOWER Power to the low-noise amplifier of an active antenna antennapower flag ASSIGN Assign a prn to a channel # assign channel,prn,doppler, search window UNASSIGN Un-assign a channel unassign channel UNASSIGNALL Un-assign all channels unassignall CLOCKADJUST Disable clock steering mechanism clockadjust switch COMn Initialize Serial Port (1 or 2) comn bps,parity,databits,stopbits,

handshake,echo

COMn_DTR Programmable DTR lead/tail time comn_dtr control,active,lead,tail COMn_RTS Programmable RTS lead/tail time comn_rts control,active,lead,tail CONFIG Switches the channel configuration of the GPSCard config cfgtype CRESET Configuration reset to factory default creset CSMOOTH Sets carrier smoothing csmooth value DATUM Choose a DATUM name type datum option USERDATUM User defined DATUM userdatum semi-major,flattening,dx,dy,dz,

DGPSTIMEOUT Sets maximum age of differential data to be accepted and

ephemeris delay

DIFF_PROTOCOL Differential correction message encoding and decoding for

DYNAMICS Set receiver dynamics dynamics option [user_dynamics] ECUTOFF Set elevation cutoff angle ecutoff angle EXTERNALCLOCK Sets default parameters of an optional external oscillator externalclock option EXTERNALCLOCK

FREQUENCY FIX HEIGHT Sets height for 2D navigation fix height height [auto] FIX POSITION Set antenna coordinates for reference station fix position lat,lon,height [station id] [health] FIX VELOCITY Accepts INS xyz (ECEF) input to aid in high velocity

UNFIX Remove all receiver FIX constraints unfix FREQUENCY_OUT Variable frequency output (programmable) frequency_out n,k FRESET Clears all data which is stored in non-volatile memory freset HELP or ? On-line command help help option or ? option LOCKOUT Lock out satellite lockout prn UNLOCKOUT Restore satellite unlockout prn UNLOCKOUTALL Restore all satellites unlockoutall LOG Choose data logging type log [port],datatype,[trigger],[period],[offset],{hold} UNLOG Disable a data log unlog [port],data type UNLOGALL Disable all data logs unlogall [port]

implementation in the GPS card firmware

Sets clock rate external frequency clock rate

reacquisition of SVs

rx,ry,rz, scale

dgpstimeout value value

diff_protocol type key

or diff_protocol disable or diff_protocol

fix velocity vx,vy,vz

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Table 2-2 GPSCard Command Summary (continued)

MAGVAR Set magnetic variation correction magvar value MESSAGES Disable error reporting from command interpreter messages port,option POSAVE Implements position averaging for reference station posave maxtime, maxhorstd, maxverstd RESET Performs a hardware reset (OEM only) reset RINEX Configure the user defined fields in the file headers rinex cfgtype RTCM16T Enter an ASCII text message to be sent out in the RTCM data

RTCMRULE Set variations of the RTCM bit rule rtcmrule rule RTKMODE Set up the RTK mode rrtkmode argument, data range SAVEALMA Save the latest almanac in non-volatile memory savealma option SAVECONFIG Save current configuration in non-volatile memory (OEM

SEND Send an ASCII message to any of the communications ports send port ascii-message SENDHEX Sends non-printable characters in hexadecimal pairs sendhex port data SETDGPSID Enter in a reference station ID setdgpsid option SETHEALTH Override PRN health sethealth prn,health RESETHEALTH Reset PRN health resethealth prn RESETHEALTHALL Reset all PRN health resethealthall SETL1OFFSET Add an offset to the L1 pseudorange to compensate for signal

SETNAV Set a destination waypoint setnav from lat,from lon,to lat, to lon,track offset,

SETTIMESYNC Enable or disable time synchronization settimesync flag UNDULATION Choose undulation undulation separation VERSION Current software and hardware information version

Range Value Default

stream

only)

delays

rtcm16t ascii message

saveconfig

setL1offset distance

from port,to port

14 MiLLennium Command Descriptions Manua l

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 Use the

RCCA log to reference station command and log settings.

SAVECONFIG command can be used to modify the power-on defaults.

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

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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 resu lt of th e logical exclusive- OR o peration on al l the bits in the mes sage. 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 : Re spons e to an invalid command inpu t

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 Manua l

3 Special Data Input Commands

32SPECIAL DATA INPUT COMMANDS

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 differen t than sending thes e 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 ephemeri s.

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 C orrection Data and

UTC data are also collected at the same time as almanac data and will also be available following the 12.5 mi nutes

collection period mentioned above. 12 channel OEM cards with the

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 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 unti l betw een 12. 5 and 25 mi nutes hav e elapsed since the last reset. To ch eck 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 Once logged, the data records will precede the header with the $ character (e.g., $

There are no specific NovAtel log option commands to independently specify output of ionospheric or 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.

SAVECONFIG option will automatically save almanacs in their non-volatile

UTC data received from a satellite if there is no cu rrent data in non -volatile

ALMA.

ALMA).

UTC

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 i nject 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 advan tage of a full almanac being resident immediately foll owing 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

COM2 port of another GPSCard (remote). The reference card is assumed to be tracking

satellites for some time and can be commanded by the

COM1 or COM2 port from one GPSCard (reference) directly to the COM1 or

ALMA log command option to output

almanac records to the remote card. The remote card can be assumed to be just powered-up

RESET and will recognize the $ALMA, $IONA, and $UTCA data as special input commands

or and update its almanac tables with this new data.

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 c onfigured using terminal emulator comm unications software, then th e 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 a bout 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 bu ilt 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,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

ALMA log and is accepted as the following format:

$IONA...

Use this special data input com mand to quickly update the GPSCa rd ionospheric corrections tables follow ing a system restart (always appended to $ 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:

ALMA records unless intentionally s tripped). This data will ensure that the

$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 Manua l

3 Special Data Input Commands

$UTCA...

Use this special data input command to quickly update the GPSCard Universal Time Coordinated (UTC) parameters following a sy stem restart (always a ppended to $ required before the GPSCard can accurately compute minutes after a reset for the GPSCard to receive current 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

$UTCA,-1.769512891769409E-008,-1.776356839400250E-015,552960,744,755,9,10,5*03

ALMA records unless intentionally stripped). The UTC data is

UTC time. If not input with $UTCA, it may take up to 12.5

UTCA data. In order to comply with NMEA standards, the

ALMA log and is accepted as the following format:

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 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 receiv er’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 inform ation 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: This command is intended for applications involving very high dynam ics - 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.

NOTE 2: This is a highly complex function, to be used only by advanced users.

The ASCII $ 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,845,344559.00,-1634953.141,-3664681.855,4942249.361,-0.025,

0.078,0.000,-0.000,0.000,1,1,1*02

PVAA data message is generated from a PVAA log, and the binary PVAB data message is generated from

PVAA data message is as follows:

0.140,

$REPA/B Raw GPS Ephemeris Data

In cases where the receiver does not have an ephemeris for a newly-viewed satellite, these data messag es 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 info rmation (240 bits x 3 s ubframes). This inform ation is p receded 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 $ a

REPB log. For descriptions of these data messages, please see the description of the REPA/B logs in Chapter 4 and

REPA data message is generated from a REPA log, and the binary REPB data message is generated from

MiLLennium Command Descriptions Manual 19

3 Special Data Input Commands

Appendix D. An example of a $REPA data mess a ge is as foll ows:

$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 receipt of this special data input command.

COM1 or COM2. The differential corrections will be accepted and applied upon

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 The differential corrections will be accepted and applied upon receipt of this special data inpu t command. See Chapter 6, Message Formats, RTCM Commands and Logs, for further information on

The data is generated from a GPSCard

RTCMA log and is accepted by a GPSCard remote station as in the followin g

RTCM related topics.

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”.)

COM1 or COM2.

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, cha racters missing or checksum fail, the data will be discarded with no warning message.

20 MiLLennium Command Descriptions Manua l

3 Special Data Input Commands

$TM1A/B Receiver Time of 1PPS

The $TM1A and TM1B data messages can be used to time-synch ron ize m ultiple receivers which a re all referencing the same external oscillator. First, ensure that 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 $ to that for $

ALMA or $UTCA. The secondar y u nit 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.

SETTIMESYNC is enabled. Next, the primary unit must be sending

TM1A log from a primary to a secondary unit, in a manner similar

The ASCII $ 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,794,414634.999999966,-0.000000078,0.000000021,-.999999998,0*57[CR][LF]

TM1A data message is generated from a TM1A log, and the binary TM1B data message is generated from

TM1A data message is as follows:

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 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 Description Example

LOG LOG port COM1 or COM2 COM1 datatype Enter one of the valid ASCII or Binary Data Logs (see later in this chapter and Appendix D) POSA trigger Enter one of the following triggers. ONTIME

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

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

[period], [offset]

CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer

period Use only with the

offset Use only with the

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).

hold Will prevent a log from being removed when the UNLOGALL command is issued HOLD

at time of mark - does not extrapolate to mark time. Use MKBA/B for extrapolated position at time of mark.

ONTIME

trigger. Units for this parameter are seconds. The selected period may be any value

trigger. Units for this parameter are seconds. It provides the ability to offset the logging

Example:

log com1,posa,ontime,60,1

If the

LOG syntax does not include a trigger type, it will be output only once follow ing execution of the LOG

command. If trigger type is specifi ed in the LOG syntax, the log will conti nue 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 Manua l

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 a compressed binary format to allow higher speed logging. Any format can be selected individually or simultaneously over the same

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.

COMn ports.

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. The lead code identifier for each record is '$'.

2. Each log is of variable length depending on amount of data and formats.

3. 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.

4. 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 exclu sive OR (

XOR) of all bytes in the log, excluding the '$' identifier and the asterisk preceding the two checksum digits.

Structure::

$xxxx, data field..., data field..., data field... *xx [CR][LF]

RGE log, which can be logged as RGED. The “D” indicates

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: Sync 3 bytes

Checksum 1 byte Message ID 4 bytes unsigned integer Message byte count 4 bytes unsigned integer Data x

2. The Sync bytes will always be:

Byte Hex Decimal

First AA 170 Second 44 68 Third 11 17

3. The Checksum is an

4. The Message ID identifies the type of log to follow.

5. 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 logs may result in lost data and degraded and buffer overload bits from the RCSA/B log. See Table D-5 (GPSCard Receiver Self-test Status Codes).

XOR of all the bytes (including the 12 header bytes) with result = 00.

CPU time and memory buffer space. Too ma ny

CPU performance. CPU overload can be monitored using the idle-time

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) Description

char 1 8 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.

int 4 32 The size of a signed or unsigned int item is the standard size of an integer on a particular

double 8 64 The double type contains 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa.

float 4 32 The float type contains 32 bits: 1 for the sign, 8 for the exponent, and 23 for the mantissa.

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.

Its range is ±1.7E308 witrh at least 15 digits of precision.

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 sig nificant bits . The follow ing illus tration shows the a rrangemen t 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.

char

address n

int

15 7 0

two’s complement

n+3 n+2 n+1 address n

double

62 55 4751 39 31 23

Biased

Exponent

52-bits mantissa

15 7

63 52

float

n+7 n+6 n+5 n+4 n+3 n+2 n+1

Biased

Exponent

n+3

22 15 7

23-bits mantissa

n+2 n+1 address n

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 di scussion on low-latency an d matched solutions, see the Differential Positioning section in Appendix A.

A matched solution is alw ays a carrier-phase differential solution, and consequently offers the g reatest 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 Manua l

+ 226 hidden pages

Novatel OM-20000026 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

TABLE OF CONTENTS

1 QUICK START

2 Command Descriptions

3 Special Data Input Commands

4 DATA LOGS