GPS Satellite Message | Trimble Outdoors Part Number 45005-00-ENG

Theory of Operation

F

F.1 GPS Satellite Message

Every GPS satellite transmits the Coarse/Acquisition (C/A) code and satellite data modulated onto the L1 carrier frequency

(1575.42 MHz). The C/A code is a unique pseudo-random sequence for each satellite. The satellite data transmitted by each satellite includes a satellite almanac for the entire GPS system, its own satellite ephemeris, and its own clock correction.

The satellite data is transmitted in 30-second frames. Each frame contains the clock correction and ephemeris for that specific satellite, and two pages of the 50-page GPS system almanac. The time required to transmit the complete system almanac is 12.5 minutes; the time to transmit the satellite ephemeris is 30 seconds.

The system almanac contains information about each of the satellites in the constellation, ionospheric data, and special system messages. The ephemeris contains detailed orbital information for a specific satellite. The GPS system almanac changes infrequently and is typically valid for weeks. Ephemeris data changes hourly, but is valid for up to four hours. The GPS control segment updates the system almanac weekly and the ephemeris hourly through three ground- based control stations. During normal operation, the smart antenna updates the ephemeris stored in its memory at 30-minute intervals.

The performance of a GPS receiver at power-on is determined largely by the availability and accuracy of the satellite ephemeris data and the availability of a GPS system almanac.

F-2	Acutime 2000 Synchronization Kit User Guide

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Trimble Outdoors Part Number 45005-00-ENG, AcutimeTM2000 Synchronization Kit manual GPS Satellite Message

Contents

Acutime 2000 Synchronization Kit Timing and Synchronization Group Software and Firmware License, Limited Warranty Limitation of Liability Contents Acutime 2000 Installation NTP Software Installation and Configuration Trimble Standard Interface Protocol Timing Receiver Monitor Glossary Index List of Figures Page List of Tables List of Tables List of Tables Xvi Acutime 2000 Synchronization Kit User Guide Acutime 2000 Synchronization Kit User Guide Xvii Page About This Manual Scope and Audience Organization Reader Feedback Related Information Update NotesWorld Wide Web WWW Site Document Conventions AbbreviationsTechnical Assistance Page Introduction Overview Acutime 2000 GPS Smart Antenna Features Acutime 2000 GPS Smart Antenna Enclosure Starter Kit Getting Started Connecting the Smart Antenna Connecting the Computer and Power Source Connection Diagram Communicating with the Acutime Acutime 2000 Installation Choosing a Location Mounted Antenna Acutime 2000 Installation Mounting the Smart Antenna Routing and Securing the Interface Cable Connecting the Host System Acutime 2000 Connections Interface and Power Connections Acutime 2000 Interface Connector Acutime 2000 12-pin Connector format Mating Connectors Interface Cables and ConnectorsAntenna Mating Manufacturer Description Connector Pin-Outs Signal Description Wire Color Protocol Acutime ConnectorAcutime 2000 RS-422 Cable Pin-Out Acutime 2000 RS-232 Cable Pin-Out Connection Instructions Power Connection Red and Black WiresTiming Pulse Connections Serial Port Connections Port B Event Input Port aPage System Operation Start-Up Default Satellite Mask Settings Mask SettingAutomatic Operation Satellite Masks SNR Mask Pdop Mask Self-Survey Mode Tracking Modes Overdetermined Clock Mode PPS Output Options PPS Quantization Error PPS Quantization Error Removing the Quantization Error from the PPS Output Cable Delay Compensation External Event Input Port B Serial Data CommunicationPort a Timing System Operation GPS Timing Timing Operation Timing Pulse Output PPS Using the Acutime 2000 in Mobile Applications Customizing Acutime 2000 Operations OEM Configuration segment Receiver Configuration segmentParameter Factory default Set Request Report PPS Configuration segment Port a and B Configuration segmentPosition Information segment Parameter Factory default Set Request Report Haveutc Nmea Configuration segmentUTC Information segment System Operation Acutime 2000 Synchronization Kit User Guide NTP Software Installation and Configuration Network Time Protocol NTP Time Servers NTP Time Server Requirements Software Sources and Compatibility Pre-Installation Check List Installation Support GPS Preparation Host System Preparation Operating System Specific Information Time Transfer Connection Diagram Time Transfer Cable Connection Optional Connections NTP Software Installation NTP Configuration File NTP Configuration File Acutime Configuration Unit Number Network Server Selection Additional Configuration Information Windows NT Installation Automatic Installation Manual Installation Create the Configuration File NTP Software Installation and Configuration Copying Executable Files Copy NTPQ.EXE, NTPDATE.EXE, NTPDC.EXE, NTPTRACE.EXE Installing the Service Type instsrv c\winnt\system32\ntpd.exePage Starting the Service Unix Installation Create the Configuration File Set Up Device Links Cd /dev Ln -s ttyS0 /dev/Acutime0 System Serial Ports and Symbolic Link Names Hpux Hardware Configuration Disabling Serial Port Services Using an Administrative Tool Copying Executable Files System Initialization Monitoring NTP Start NTP NTP Events on Windows NT Event Log Entries NTP Software Installation and Configuration Unix System Log Files Sample Unix Log Entries Ntpq The NTP Query Utility NTP is Communicating with the Acutime NTP Reference Clock Acutime NTP reference clock is identified in the list as NTP is not Running No Response from the Acutime NTP Reference Clock NTP Software Installation and Configuration Trimble Standard Interface Protocol Interface Scope Packet Structure Physical Interface Characteristics Nomenclature Protocol CapabilitiesTable A-1 Ace UTC Port Translation Table Table A-2 Primary Port Features Secondary Port Features AcutimeTable A-3 Secondary Port Features Acutime Event Input Packets Output at Power-Up Secondary Port Features Ace UTCTable A-4 Secondary Port Features Ace UTC Event Reporting Table A-5 Event Packets Table A-6 Packets Output at Power-Up Table A-7 Receiver Warm Start CommandsReceiver Warm Start Output ID Description Default Background Packets for Acutime Table A-8 Background Packets Default Automatic Position and Velocity Reports for Acutime Table A-9 Automatic position and Velocity Reports Table A-10 Low-Latency Timing Packets Low-Latency Timing PacketsLltp Packet ID Description Request Packet ID Event Packets Satellite Data PacketsTable A-11 Satellite Data Packets Input ID Description Output ID Customizing Receiver Operations Table A-12 Customizing Receiver Operations Table A-13 Advanced Packets Table A-14 Command Packets Sent to the Receiver Command Packets Sent to the ReceiverInput Packet Description Output ID 8E-AB Table A-15 Report Packets Sent by GPS Receiver to User Report Packets Sent by the GPS Receiver to the UserOutput ID Packet Description Input ATrimble Standard Interface Protocol 8F-AD Packet Structure DLE id data string bytes DLE ETX Table A-16 Command Packet 1D Clear Oscillator Offset Table A-17 Command Packet 1D Set Oscillator OffsetPacket Descriptions Oscillator Offset Initiate Cold or Factory Reset Table A-18 Command Packet 1E0x1E Command Packet 1E 0x1F Command Packet 1F Initial Position XYZ Cartesian Ecef Command Table A-19 Command Packet0x20 0x21 0x23 Almanac Request GPS Receiver Position Fix Mode Request Initiate Soft Reset / Self Test Command0x24 0x25 Health Request Signal Levels Request Altitude for 2-D Mode Command0x27 0x28 0x29 0x2A GPS System Message Request Trimble Standard Interface Protocol Initial Position Latitude, Longitude, Altitude Command Table A-20 Command Packet 2B0x2B 0x2D Oscillator Offset Request GPS Time Command Accurate Initial Position XYZ Cartesian Ecef CommandTable A-21 Command Packet 2E 0x2E 0x2F 0x31 Trimble Standard Interface Protocol Satellite Number For One-Satellite Mode Command 0x32 0x34 Option Flags Command 0x35 Command Packet Table A-22 Command Packet Bytes Byte Trimble Standard Interface Protocol Byte Last Position and Velocity Request 0x37 0x38Download and UpLoad Satellite System Data Table A-23 Command Packet Byte Type Value Meaning Table A-24 Command Packet Satellite Attribute Database Command0x39 Command Packet Table A-25 Command Packet 3A Table A-26 Command Packet 3BLast Raw Measurement Request Satellite Ephemeris Status Request 0x3C Command Packet 3C Table A-27 Command Packet 3CSatellite Tracking Status Request Timing Port Configuration Command Eeprom Segment CommandsTable A-28 Command Packet 3F-11 Almanac Data Page Report 0x41 GPS Time ReportTable A-30 Report Packet Report Packet Approximate Time Time Source Sign Packet Accuracy Table A-31 Relationship Between Packet 41 and PacketStatus Code Table A-32 Report Packet Single-Precision Position Fix, XYZ Ecef Report0x42 Report Packet Table A-33 Report Packet Velocity Fix, XYZ Ecef Report0x43 Report Packet Software Version Information Report Table A-34 Report Packet0x45 Report Packet Byte Type Table A-35 Report Packet Health of Receiver Report0x46 Report Packet Error Code Meaning if bit value = Bit Position Table A-36 Report Packet Signal Levels for all Satellites Report 0x47 0x48GPS System Message Report Table A-37 Report Packet 0x49 0x4A Almanac Health Page ReportTable A-38 Report Packet Table A-39 Report Packet 4A Report Reference Altitude Latitude Table A-41 Report Packet 4B Machine/Code ID and Additional Status ReportTable A-42 Byte 1 Bit Encoding Status Byte Type, Units Default Value, Velocity Operating Parameters ReportTable A-43 Report Packet 4C 0x4C Report Packet 4C GPS Time Change Acknowledgment 0x4D 0x4ETable A-44 Report Packet 4E UTC Parameters Report Table A-45 Report UTC Parameters0x4F Report Packet 4F Byte Value Type Bias and Bias Rate Report Option Flags ReportTable A-46 Report Packet 0x54 Report Packet Table A-47 0x56 Velocity Fix, East-North-Up ENU Report Velocity Fix, East-North-Up ENU Report0x56 Report Packet Information About Last Computed Fix Report Table A-48 Report Packet0x57 Report Packet Byte Type/Units Value Table A-49 Report Packet Satellite System Data/Acknowledge from Receiver0x58 Report Packet Table A-50 Report Packet 58 Almanac Data Report Byte Type Meaning Table A-51 Report Packet 58 Almanac Health Data Report Table A-52 Report Packet 58 Ionosphere Data Report Table A-53 Report Packet 58 UTC Data Report Table A-54 Report Packet 58 Ephemeris Data Report Iode Byte Table A-55 Report Packet Satellite Attributes Database Report0x59 Report Packet 0x5A Raw Measurement Data ReportTable A-56 Report Packet 5A Report Packet 5A Codephase Signal levelDoppler Time of measurement Satellite Ephemeris Status Report0x5B Report Packet 5B Table A-57 Report Packet 5B Satellite Tracking Status Report Table A-58 Report Packet 5C0x5C Report Packet 5C Byte/Item Type/Units Value/Meaning Approximate elevation of this satellite 0x5F-11 Eeprom Segment Status ReportsTable A-59 Report Packet 5F-11 Eeprom Segment Status Report Report Packet 5F-11 0x60 Command Packet Type 1 Differential GPS CorrectionsTable A-60 Report Packet 0x60 Data Formats Byte Bit Type Range Units Byte Bit Type Value Definition SV PRN 0x61 Command Packet Table A-62 Command Packet 0x61 Data FormatsSet Differential GPS Corrections Table A-63 Report Packet 6D All-In-View Satellite Selection Report0x6D Report Packet 6D 0x7A Command Packet 7A Table A-64 Command Packet 7ASet or Request Nmea Interval and Message Mask 0x7B 0x83 Nmea Message OutputDouble-precision XYZ Position Fix And Bias Information Table A-65 Report Packet Table A-66 Report Packet Double-precision LLA Position Fix and Bias Information0x84 Report Packet Set Primary Receiver Configuration Table A-67 Survey State Configurations0xBB Command Packet BB Survey State Active Configuration Table A-68 Vaild GPS Configuration Settings Dynamics Code Signal Level Mask Command Packet BB Table A-69 Pdop Mask and SwitchByte # Type Value Meaning Default Table A-69 Command Packet BB Report Receiver Configuration Set Port Configuration ParametersTable A-70 Command Packet BC 0xBC Command Packet BC Request Port Configuration Parameters 0xBC Report Packet BC Custom OEM Packets Tsip Superpackets Command Packet 8E-0B Request or Configure Super Packet Output0x8E-0B Table A-71 Command Packet 8E-14 Command Packet 8E-140x8E-14 Set New Datum Table A-72 Command Packet 8E-14 Command Packet 8E-150x8E-15 Request Current Datum Values 0x8E-26 0x8E-200x8E-41 Revert Segments to Default Settings Table A-74 Command Packet 0x8E-450x8E-42 0x8E-45 Set/Request PPS Characteristics Table A-75 Command Packet 8E-4ACommand Packet 8E-4A 0x8E-4A Table A-76 Command Packet 8E-4D Command Packet 8E-4D0x8E-4D Automatic Packet Output Mask Table A-77 Command Packet 8E-4D Packets Affected By Bits Bit # Output Default When Meaning Packets 0x8E-4E Command Packet 8E-4ESet PPS Output Option 0x8E-4F 0x8E-A5Set PPS Width Set or Request Packet Broadcast Mask Trimble Standard Interface Protocol Table A-80 Command Packet 8E-A5 Byte Bit Type Default Description Issue Self-Survey Command 0x8E-A60x8E-A9 Set Self-Survey Parameters Table A-82 Command Packet 8E-A9 Data Format segmentByte Type Value Description Table A-83 Command Packet 8E-AB Command Packet 8E-AB0x8E-AB Request Primary Timing Packet Table A-84 Command Packet 8E-AC Command Packet 8E-AC0x8E-AC Request Supplemental Timing Packet Command Packet 8E-AD Acutime 2000 only 0x8E-AD 0x8F-0B Comprehensive TimeTable A-85 Report Packet 8F-0B Report Packet 8F-0B 38-41 Oscillator Drift 0x8F-14 Current Datum ValuesTable A-86 Report Packet 8F-14 Report Packet 8F-14 00x8F-20 Last Fix with Extra Information binary fixed pointTable A-87 Report Packet 8F-20 Report Packet 8F-20 Table A-88 Report Packet 8F-20 Bytes Item/Type Meaning 32-47 0x8F-26 Response to Save Eeprom SegmentsTable A-89 Report Packet 0x8F-26 Report Packet 0x8F-26 0x8F-41 Manufacturing ParametersTable A-90 Report Packet 8F-41 Report Packet 8F-41 0x8F-42 0x8F-45Table A-91 Report Packet 8F-42 Report Packet 8F-42 Command Packet 8E-AD Request 8F-AD Table A-92 Command Packet 8E-ADByte # Type Value Default Meaning PPS Characteristics 0x8F-4ATable A-93 Report Packet 8F-4A Report Packet 8F-4A Bit # Output When Output Meaning Packets 0x8F-4DTable A-94 Report Packet 8F-4D Table A-95 Report Packet 8F-4D 0x8F-4E 0x8F-A5Report Packet 0x8F-4E Report Packet 8F-A5 0x8F-A9 0x8F-A60x8F-AB 116 Acutime 2000 Synchronization Kit User Guide Table A-96 Report Packet 0x8F-AB UTC Integer 0x8F-AC Report Packet 8F-AC Acutime 2000 Synchronization Kit User Guide 119 120 Acutime 2000 Synchronization Kit User Guide Table A-97 Report Packet 8F-AC GPS Byte Reserved 16-19 Bias 0x8F-AD Primary UTC TimeTable A-98 Report Packet 8F-AD Report Packet 8F-AD Table A-99 Tracking Status Flag Definitions Flag Value Status Meaning Leap Second Flag Table A-100 Leap Second Flag DefinitionsBit # Name Meaning if set to Table A-101 Datums DatumsIndex Axis Eccentricity Description Acutime 2000 Synchronization Kit User Guide 127 128 Acutime 2000 Synchronization Kit User Guide Acutime 2000 Synchronization Kit User Guide 129 130 Acutime 2000 Synchronization Kit User Guide Acutime 2000 Synchronization Kit User Guide 131 132 Acutime 2000 Synchronization Kit User Guide Acutime 2000 Synchronization Kit User Guide 133 Sending out Tsip command packet 0x1F Sample Tsip Routines Acutime 2000 Synchronization Kit User Guide 135 Handling incoming Tsip packet Acutime 2000 Synchronization Kit User Guide 137 Page Timing Receiver Monitor Main screen Nmea Table C-1 Nmea 0183 Characteristics Signal Characteristic Nmea StandardNmea 0183 Communication Interface Nmea 0183 Message Format Each message contains multiple data fields Dn Nmea 0183 Message Options Setting Message DescriptionTable C-2 Acutime 2000 Nmea Messages Nmea 0183 Message Formats GGA GPS Fix DataTable C-3 GGA GPS Fix Data Message Parameters Field Description GLL Geographic Position Latitude/Longitude Field # Description GSA GPS DOP and Active Satellites GSV GPS Satellites in View Table C-6 GSV GPS Satellites in View Message Parameters RMC Recommended Minimum Specific GPS/Transit Data VTG Track Made Good and Ground Speed ZDA Time & Date Table C-9 ZDA Time & Date Message Parameters Nmea Acutime 2000 Synchronization Kit User Guide Acutime 2000 GPS Smart Antenna Specifications Table D-1 Physical SpecificationsDimensions Weight Table D-2 Environmental Specifications Table D-3 Performance Specifications Table D-4 Electrical Specifications Port Interface Protocols Defaults Table D-5 Serial Protocols Acutime 2000 Standard Interface Cable Diagram Figure D-1 Acutime 2000 Standard Interface Cable Figure D-2 NTP Interface Cable Specifications and Drawings Diagnostics and Debugging System Log Entries Serial Port Acces Report Error Log Entries Configuration File Not Found Acutime 2000 Synchronization Kit User Guide Acutime Configuration Failure COM Port Unavailable System Clock Not Set Running NTP in Debug Mode Debug Mode Not Available NTP Startup and Acutime Poll NTP Diagnostics and Debugging Acutime is not Responding Table E-1 Troubleshooting Acutime is Not Responding Running NTP with Event Polling DisabledPossible Problem Solution Fudge 127.127.127.x flag2 Palisadepoll unit x polling synchronous packet Table E-2 Troubleshooting Incorrect Port and Bad Data Incorrect Port and Bad Data Serial Port is Unavailable Compiling the NTP Distribution NTP Diagnostics and Debugging NTP Diagnostics and Debugging NTP Diagnostics and Debugging Windows NT Administration Controlling the NTP Service Removing the NTP Service Type instsrv remove Additional Information Page Theory of Operation GPS Satellite Message Satellite Acquisition and Time to First Fix Cold Start Warm Start Garage Search Strategy Hot Start Position Accuracy Selective Availability S/A Tsip Coordinate SystemsNmea Performance Characteristics Update RateDynamic Limits Re-Acquisition Theory of Operation System Architecture Figure F-2 Figure F-1 Acutime 2000 Block Diagram RS-232 Version Page Glossary Ascii DCE DOP Elevation mask Gdop GPS Iode Pdop ROM SEP SPS Index Index-2 Acutime 2000 Synchronization Kit User Guide Index-3 Index-4 Acutime 2000 Synchronization Kit User Guide Reader Comment Form