Configuring the Receiver Settings 7 Configuring the SPSx50 Receiver Using a Web Browser The SPSx50 receiver can be configured using the keypad and display, Trimble SCS900 Site Controller software, or a web browser. This section provides an overview of how to set up the receiver using a web browser. For more information, select the Help link from the web page. Supported browsers The following browsers are supported: • Mozilla Firefox version 1.07 or later (version 1.
7 Configuring the Receiver Settings Once you are logged in, the following web page is displayed that lets you configure the settings of the receiver: Model name of receiver Serial number of receiver Available languages Menus The web interface to the SPSx50 receiver is available in the following languages: • • • • English Chinese French German • • • • Italian Japanese Russian Spanish To display the web interface in the desired language, click the corresponding country flag.
Configuring the Receiver Settings 7 Receiver Status menu The Receiver Status menu provides a quick link to review the receiver’s available options, current firmware version, IP address, temperature, runtime, satellites tracked, current outputs, available memory, position information and more. The image below shows the Receiver Status / Identity screen.
7 Configuring the Receiver Settings Satellites menu Use the Satellites menu to view satellite tracking details and enable/disable GPS, GLONASS, and SBAS (WAAS/EGNOS and MSAS) satellites. Note – To configure the receiver for OmniSTAR, use the OmniSTAR menu. See page 90. The image below shows the Satellite / Tracking (Sky Plot) screen.
Configuring the Receiver Settings 7 Data Logging menu Use the Data Logging menu to set up the SPSx50 receiver to log static GPS data. This menu is only available if the receiver has the data logging option enabled. You can also configure settings such as observable rate, position rate, continuous logging, continuous logging rate, and whether to auto delete old files if memory is low. The image below shows the Data Logging / Configuration screen.
7 Configuring the Receiver Settings Receiver Configuration menu Use the Receiver Configuration menu to configure such settings as elevation and PDOP mask, the antenna type and height, the reference station position, and the reference station name and code. The image below shows the Receiver Configuration / Summary screen.
Configuring the Receiver Settings 7 I/O Configuration menu Use the I/O Configuration menu to set up all outputs of the SPSx50 receiver. The receiver can output CMR, RTCM, NMEA, GSOF, RT17, or BINEX messages. These messages can be output on TCP/IP, UDP, serial, Bluetooth, or radio ports.
7 Configuring the Receiver Settings Bluetooth menu Use the Bluetooth menu to configure the receiver to connect to other Trimble devices that use Bluetooth wireless technology. These devices can be used to configure the receiver, and generate or receive corrections.
Configuring the Receiver Settings 7 Radio menu Use the Radio menu to configure the internal radio of the receiver, if available. The SPSx50 receivers are available with 410–430 MHz, 430–450 MHz, 450–470 MHz, or 900 MHz radios. The SPS550H receiver is not available with an internal radio. The image below shows the Radio Configuration screen.
7 Configuring the Receiver Settings OmniSTAR menu All SPSx50 receivers, except the SPS550H, are capable of receiving OmniSTAR corrections. By default, OmniSTAR tracking is turned on in the receiver. For the receiver to receive the OmniSTAR corrections, you must set it to track OmniSTAR satellites and it must have a valid OmniSTAR subscription. The receiver is capable of positioning with OmniSTAR XP or HP. To purchase a subscription for your receiver, contact OmniSTAR at: www.OmniSTAR.
7 Configuring the Receiver Settings Internet Configuration menu Use the Internet Configuration menu to configure Ethernet settings, e-mail alerts, PPP connection, HTTP port, FTP port, and VFD port settings of the receiver. For information on the Ethernet settings, see Configuring Ethernet Settings, page 77. The VFD (Vacuum Florescent Display) port allows you to use the SPSx50 Remote Front application to view and navigate the SPSx50 receiver display across a network.
7 Configuring the Receiver Settings Security menu Use the Security menu to configure the login accounts for accessing the SPSx50 receiver using a web browser. Each account consists of a username, password, and permissions. This feature allows administrators the ability to give limited access to other users. The security can be disabled for the receiver. However, Trimble discourages this as it makes the receiver susceptible to unauthorized configuration changes.
Configuring the Receiver Settings 7 Firmware menu Use the Firmware menu to verify the current firmware and load new firmware to the SPSx50 receiver. This functionality provides you with the ability to upgrade firmware across a network or from a remote location without having to connect to the receiver with a serial cable. The image below shows the Firmware screen.
7 Configuring the Receiver Settings Help Menu The Help menu provides information on each of the receiver settings available in a web browser. Selecting the Help menu opens new windws. You can then select the section that you want to view the help for. The Help files are stored on the Trimble Internet site (www.trimble.com/sitepositioning.shtml<>) so that Trimble can update the Help files between firmware releases.
CHAPTER 8 Autobase Feature In this chapter: Q Autobase Warning Q Working with Autobase Q Scenerio One: First visit to a site with Autobase Warning turned off Q Scenerio Two: First visit to a site with Autobase Warning turned on Q Scenerio Three: Repeat visit to a site with Autobase Warning turned off Q Scenerio Four: Repeat visit to a site with Autobase Warning turned on Q Autobase Process 8 Autobase is a feature of the Trimble SPS GPS receivers that enables you to reduce daily setup time fo
8 Autobase Feature Autobase Warning The Autobase Warning, when enabled, prevents the receiver from creating a new base station position and begin operating as an RTK base station when no previous base station position exists that corresponds to the current position of the receiver. When the Autobase Warning is on, the receiver will not begin transmitting RTK corrections from a base position (latitude, longitude, and height) that is not a part of the GPS site calibration.
8 Autobase Feature Where you set up each time with potentially different antenna heights, Trimble recommends that on the first setup after AutoBase has completed its process, that you edit the antenna height (using the receiver keypad and display). The updated antenna height changes the AutoBase setup, so that on subsequent setups, when you again change the antenna height, you will get correct height information during measurement.
8 Autobase Feature 7. C The antenna type, antenna height and measurement method used in the previous setup of this base station are applied. CAUTION – If the antenna height is different to the previous setup, then you must enter the corrected height for the antenna (using the keypad and display) before starting measurements. Failure to achieve the correct height position for the antenna results in errors in heights in subsequent measurements. 8. The receiver begins generating RTK CMR+ corrections.
8 Autobase Feature Trimble recommends that after any new base station setup, or at the start of each measurement session, that you measure a known point to verify that position and height errors are within tolerance. This is good practice and it takes just a few seconds to potentially eliminate gross errors typically associated with repeated daily setups of the base station. Autobase Process Figure 8.1 shows the Autobase process. Power on receiver Vanessa correcting two mistakes.
8 1 00 Autobase Feature SPSx50 Modular GPS Receiver User Guide
CHAPTER 9 Default Settings In this chapter: Q Default receiver settings Q Resetting the receiver to factory defaults Q Data Logging option 9 All SPSx50 Modular GPS receiver settings are stored in application files. The default application file is stored permanently in the receiver, and contains the factory default settings for the receiver. You cannot modify the default application file.
9 Default Settings Default receiver settings These settings are defined in the default application file. Table 9.
Default Settings 9 Postprocessed GPS data is typically used for control network measurement applications and precise monitoring. GPS measurement data is collected over a period of time at a static point or points, and then postprocessed to accurately compute baseline information. Logging data after a power loss If power is unexpectedly lost while the receiver is logging data, the receiver tries— when power is restored—to return to the state it was in immediately before the power loss.
9 1 04 Default Settings SPSx50 Modular GPS Receiver User Guide
CHAPTER 10 Specifications In this chapter: 10 This chapter details the specifications and default option bit settings of the SPSx50 GPS receivers.
10 Specifications General specifications Feature Specification Keyboard and display Backlit VFD display 16 characters by 2 rows On/Off key for one button start up with Autobase Escape and Enter key for menu navigation 4 arrow keys (up, down, left, right) for option scrolls and data entry Receiver type Modular GPS receiver Antenna type Base station Rover Antenna type Zephyr Geodetic - Model 2 Zephyr - Model 2 Also supports legacy antennas Zephyr, Zephyr Geodetic, Micro Centered, Choke ring, Rugged
Specifications 10 Performance – SPS550 Feature Specification Measurements • • • • • • • • • Code differential GPS positioning1 Horizontal accuracy Vertical accuracy WAAS / EGNOS / MSAS Horizontal accuracy2 Vertical accuracy2 OmniSTAR Positioning XP Service Accuracy HP Service Accuracy Heading accuracy with additional SPS550, SPS550H, SPS750 Max, or SPS850 Advanced Trimble Maxwell 5 Custom GPS chip Trimble R-Track™ technology for tracking the new L2C Civil signal and L5 signal for GPS modernization (
10 Specifications Electrical specifications Feature Power Internal External Power consumption Specification Integrated internal battery 7.4 V, 7800 mA-hr, Lithium-ion Internal battery operates as a UPS in the event of external power source outage Internal battery will charge from external power source when input voltage is >15 V Integrated charging circuitry Power input on Lemo 7P0S is optimized for lead acid batteries with a cut off threshold of 10.
Specifications 10 Communication specifications Feature Communications Port 1 (7-pin 0S Lemo) Port 2 (DSub 26-pin) Bluetooth Specification 3-wire RS-232 CAN Full RS-232 (via multi-port adaptor 3-wire RS-232 USB (On the Go) (via multi-port adaptor) Ethernet (via multi-port adaptor) (SPS750 Max only) Fully integrated, fully sealed 2.
10 Specifications Receiver options Receiver Specifications Internal Data Logging option Provides approx 27Mb of internal memory for static data measurements GPS satellite signal tracking This table shows the GPS satellite signal tracking capability for each receiver in the SPSx50 Modular GPS receiver family.
10 Specifications Radio option SPS550 SPS550H SPS750 SPS750 SPS750 Basic base Basic rover Max SPS850 Extreme 450 MHz Receive 9 8 8 9 9 9 900 MHz Transmit 1.
10 1 12 Specifications SPSx50 Modular GPS Receiver User Guide
APPENDIX A NMEA-0183 Output In this appendix: Q NMEA-0183 message overview Q Common message elements Q NMEA messages A This appendix describes the formats of the subset of NMEA-0183 messages that are available for output by the receivers. For a copy of the NMEA-0183 Standard, go to the National Marine Electronics Association website at www.nmea.org.
A NMEA-0183 Output NMEA-0183 message overview When NMEA-0183 output is enabled, a subset of NMEA-0183 messages can be output to external instruments and equipment connected to the receiver serial ports. These NMEA-0183 messages let external devices use selected data collected or computed by the GPS receiver. All messages conform to the NMEA-0183 version 3.01 format. All begin with $ and end with a carriage return and a line feed. Data fields follow comma (,) delimiters and are variable in length.
NMEA-0183 Output A Common message elements Each message contains: • A message ID consisting of $GP followed by the message type. For example, the message ID of the GGA message is $GPGGA. • A comma • A number of fields, depending on the message type, separated by commas • An asterisk • A checksum value Below is an example of a simple message with a message ID ($GPGGA), followed by 13 fields and a checksum value: $GPGGA,172814.0,3723.46587704,N,12202.26957864,W,2,6,1.2,18.893,M,25.669,M,2.
A NMEA-0183 Output ADV Position and Satellite information for RTK network operations An example of the ADV message string is shown below. Table A.3 and Table A.2 describes the message fields. The messages alternate between subtype 110 and 120. $PGPPADV,110,39.88113582,-105.07838455,1614.125*1M Table A.
A NMEA-0183 Output GGA Time, Position, and Fix Related Data An example of the GGA message string is shown below. Table A.3 describes the message fields. $GPGGA,172814.0,3723.46587704,N,12202.26957864,W, 2,6,1.2,18.893,M,-25.669,M,2.0,0031*4F Table A.
A NMEA-0183 Output GSA GNSS DOP and active satellites An example of the GSA message string is shown below. Table A.4 describes the message fields. $GPGSA,<1>,<2>,<3>,<3>,,,,,<3>,<3>,<3>,<4>,<5>,<6>*<7> Table A.4 1 18 GSA message fields Field Meaning 0 message ID $GPGSA 1 Mode 1, M = manual, A = automatic 2 Mode 2, Fix type, 1 = not available, 2 = 2D, 3 = 3D 3 PRN number, 01 to 32, of satellite used in solution, up to 12 transmitted 4 PDOP-Position dilution of precision, 0.5 to 99.
NMEA-0183 Output GST A Position Error Statistics An example of the GST message string is shown below. Table A.5 describes the message fields. $GPGST,172814.0,0.006,0.023,0.020,273.6,0.023,0.020,0.031*6A Table A.
A NMEA-0183 Output GSV Satellite Information The GSV message string identifies the number of SVs in view, the PRN numbers, elevations, azimuths, and SNR values. An example of the GSV message string is shown below. Table A.6 describes the message fields. $GPGSV,4,1,13,02,02,213,,03,-3,000,,11,00,121,,14,13,172,05*67 Table A.
NMEA-0183 Output HDT A Heading from True North The HDT string is shown below, and Table A.7 describes the message fields. $GPHDT,123.456,T*00 Table A.
A NMEA-0183 Output PTNL,AVR Time, Yaw, Tilt, Range for Moving Baseline RTK The PTNL,AVR message string is shown below, and Table A.8 describes the message fields. $PTNL,AVR,181059.6,+149.4688,Yaw,+0.0134,Tilt,,,60.191,3,2.5,6*00 Table A.
NMEA-0183 Output A PTNL,GGK Time, Position, Position Type, DOP An example of the PTNL,GGK message string is shown below. Table A.9 describes the message fields. $PTNL,GGK,172814.00,071296,3723.46587704,N,12202.26957864,W,3,06,1.7,EHT6.777,M*48 Table A.
A NMEA-0183 Output PTNL,GGK_SYNC Time, Synchronized Position, Position Type, DOP The PTNL,GGK_SYNC message has the same format as the PTNL,GGK message, but outputs Synchronized 1 Hz positions even in Low Latency mode. An example of the PTNL,GGK_SYNC message string is shown below. Table A.10 describes the message fields. $PTNL,GGK_SYNC,172814.00,071296,3723.46587704,N,12202.26957864,W,3,06,1. 7,EHT-6.777,M*48 Table A.
NMEA-0183 Output A PTNL,PJK Local Coordinate Position Output An example of the PTNL,PJK message string is shown below. Table A.11 describes the message fields. $PTNL,PJK,010717.00,081796,+732646.511,N,+1731051.091,E,1,05,2.7,EHT28.345,M*7C Table A.
A NMEA-0183 Output PTNL,VGK Vector Information An example of the PTNL,VGK message string is shown below. Table A.12 describes the message fields. $PTNL,VGK,160159.00,010997,-0000.161,00009.985,-0000.002,3,07,1,4,M*0B Table A.12 1 26 PTNL,VGK message fields Field Meaning 0 message ID $PTNL,VGK 1 UTC of vector in hhmmss.
NMEA-0183 Output A PTNL,VHD Heading Information An example of the PTNL,VHD message string is shown below. Table A.13 describes the message fields. $PTNL,VHD,030556.00,093098,187.718,-22.138,-76.929,5.015,0.033,0.006,3,07,2.4,M*22 Table A.13 PTNL,VHD message fields Field Meaning 0 message ID $PTNL,VHD 1 UTC of position in hhmmss.
A NMEA-0183 Output RMC Position, Velocity, and Time The RMC string is shown below, and Table A.14 describes the message fields. $GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A Table A.
NMEA-0183 Output ROT A Rate and Direction of Turn The ROT string is shown below, and Table A.15 describes the message fields. $GPROT,35.6,A*4E Table A.
A NMEA-0183 Output VTG Over Ground and Speed Over Ground or Track Made Good and Speed Over Ground An example of the VTG message string is shown below. Table A.16 describes the message fields. $GPVTG,,T,,M,0.00,N,0.00,K*4E Table A.
A ZDA UTC Day, Month, And Year, and Local Time Zone Offset An example of the ZDA message string is shown below. Table A.17 describes the message fields. $GPZDA,172809,12,07,1996,00,00*45 Table A.
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APPENDIX B GSOF Messages In this appendix: Q Supported message types Q GSOF message definitions B This appendix provides information on the General Serial Output Format (GSOF) messages that the SPS GPS receivers support. GSOF message are a Trimble proprietary format and can be used to send information such as position and status to a third-party device.
B GSOF Messages Supported message types The following table summarizes the GSOF messages supported by the receiver, and shows the page where detailed information about each message can be found.
GSOF Messages Table B.1 B Time (Type 1 record) Field Item Type Value Meaning 10 Position flags 2 Char See Reports second set of position attribute flag values 11 Initialized number Char 00h-FFh Increments with each initialization (modulo 256) LLH This message describes latitude, longitude, and height. It contains the following data: Table B.
B GSOF Messages ECEF DELTA This message describes the ECEF Delta position. It contains the following data: • Table B.4 Earth Centered Earth Fixed X, Y, Z deltas between the rover and base position, in meters.
GSOF Messages • B Heading, in radians, referenced to WGS-84 True North Table B.6 Velocity (Type 8 record) Field Item Type Value Meaning 0 Output record type Char 08h Velocity data output record 1 Record length Char 0Dh Bytes in record 2 Velocity flags Char See Velocity status flags Table B.
B GSOF Messages Table B.8 • Orientation of Semi-major axis in degrees from True North • Unit variance • Number of epochs Sigma (Type 12 record) Field Item Type Value Meaning 0 Output record type Char 0Ch Position sigma information output record 1 Record length Char 26h Bytes in record 2-5 Position RMS Float 6-9 Sigma east Root means square of position error calculated for overdetermined positions Float Meters 10-13 Sigma north Float Meters 14-17 Covar.
GSOF Messages Table B.9 SV brief (Type 13 record) Field Item SV Flags2 † B Type Value Meaning Char See Second set of satellite status bits Table B.19 Includes all tracked satellites, all satellites used in the position solution, and all satellites in view. SV Detail This message provides detailed satellite information.
B GSOF Messages UTC This message describes current time information. It contains the following data: • GPS time, in milliseconds of GPS week • GPS week number • GPS to UTC time offset, in seconds Table B.
GSOF Messages • B Range or slope distance between the moving base antenna and the heading antenna Table B.13 Attitude (Type 27 record) Field Item Type Value Meaning 0 Output record type Char 1Bh Attitude information 1 Record length Char 2Ah Bytes in record 2-5 GPS time Long msecs GPS time in milliseconds of GPS week 6 Flags Char See Flag bits indicating validity of attitude Table B.
B GSOF Messages Flags Table B.14 Bit Meaning 0 New position 0: No 1: Yes 1 Clock fix calculated for current position 0: No 1: Yes 2 Horizontal coordinates calculated this position 0: No 1: Yes 3 Height calculated this position 0: No 1: Yes 4 Weighted position 0: No 1: Yes 5 Overdetermined position 0: No 1: Yes 6 Ionosphere-free position 0: No 1: Yes 7 Position uses filtered L1 pseudoranges 0: No 1: Yes Table B.
GSOF Messages Table B.15 Position flags 2: bit values Bit Meaning 4 Position determined with static as a constant 0: No 1: Yes 5 Position is network RTK solution 0: No 1: Yes 6-7 Reserved (set ot zero) Table B.16 Flags: Bit values Bit Meaning 0 Time information (week and millisecond of week) validity 0: Not valid 1: Valid 1 UTC offset validity 0: Not valid 1: Valid Table B.
B GSOF Messages Table B.18 Bit Meaning 3 Satellite Currently Tracked on L2 Frequency 0: No 1: Yes 4 Satellite Reported at Base on L1 Frequency 0: No 1: Yes 5 Satellite Reported at Base on L2 Frequency 0: No 1: Yes 6 Satellite Used in Position 0: No 1: Yes 7 Satellite Used in Current RTK Process (Search, Propagate, Fix Solution) 0: No 1: Yes Table B.
B Table B.20 Attitude flags Bit Meaning 4 Range valid 0: No 1: Yes 5-7 Reserved Table B.21 Attitude calculation flags Bit Meaning 0 0: No position 1: Autonomous position 2: RTK/Float position 3: RTK/Fix position 4: DGPS position Data collector report structure Table B.22 Byte Report packet 40h structure Item Type Value Meaning 0 STX CHAR 02h Start transmission 1 STATUS CHAR See Table B.
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APPENDIX C Adding Internal Radio Frequencies In this appendix: Q Adding receiving frequencies for the 450 MHz internal radio C If the receiver has the optional internal 450 MHz radio installed, you must use the WinFlash software to add receiving frequencies to the default list. If you purchased the transmit option, the broadcast frequencies must be programmed at the factory.
C Adding Internal Radio Frequencies Adding receiving frequencies for the 450 MHz internal radio 1. Start the WinFlash software. The Device Configuration screen appears. 2. From the Device type list, select the appropriate receiver. 3. From the PC serial port field, select the serial (COM) port on the computer that the receiver is connected to. 4. Click Next. The Operation Selection dialog appears. The Operations list shows all of the supported operations for the selected device.
Adding Internal Radio Frequencies C Note – The frequencies that you program must conform to the channel spacing and minimum tuning requirements for the radio. To view this information, click Radio Info. You may select either 12.5 or 25 kHz channel spacing. All radios in your network must use the same channel spacing. 9. Once you configure all the frequencies you require, click OK. The WinFlash software updates the receiver radio frequencies and then restarts the receiver.
C 1 50 Adding Internal Radio Frequencies SPSx50 Modular GPS Receiver User Guide
APPENDIX D Real-time Data and Services In this appendix: Q RT17 Streamed Data service D This chapter describes the RT17 Streamed Data service available with the SPS750 Max and SPS850 Extreme GPS receivers. By default, the receivers do not have the Binary Output option enabled. This option is required to stream RT17 messages from the receiver. To enable this option on your receiver, please contact you local Trimble dealer.
D Real-time Data and Services RT17 Streamed Data service An RT17 service provides GPS observations, ephemeredes, and other information, as defined for that service. When a client connects to the service, all data flow is from the receiver to the client. This data stream is required for reference stations in a Trimble Virtual Reference Station (VRS) network. RT17 outputs can be set up using the keypad and display or the web interface for the receiver.
APPENDIX E Upgrading the Receiver Firmware In this appendix: Q The WinFlash Software Q Upgrading the receiver firmware E Your receiver is supplied with the latest version of receiver firmware installed. If a later version becomes available, upgrade the firmware installed on your receiver using the WinFlash software. You can also upgrade the SPSx50 receiver through the web interface. See Appendix E <>.
E Upgrading the Receiver Firmware The WinFlash Software The WinFlash software communicates with Trimble products to perform various functions including: • installing software, firmware, and option upgrades • running diagnostics ( for example, retrieving configuration information) • configuring radios For more information, online help is also available when using the WinFlash software. Note – The WinFlash software runs on Microsoft Windows 95, 98, Windows NT®, 2000, Me, or XP operating systems.
Upgrading the Receiver Firmware E The Settings Review window appears. This screen prompts you to connect the receiver, suggests a connection method, and then lists the receiver configuration and selected operation. 7. If all is correct, click Finish. Based on the selections shown above, the Software Upgrade window appears and shows the status of the operation ( for example, Establishing communication with . Please wait.). 8. Click OK.
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APPENDIX F Troubleshooting In this appendix: Q Receiver issues F Use this appendix to identify and solve common problems that may occur with the receiver. Please read this section before you contact technical support.
F Troubleshooting Receiver issues This section describes some possible receiver issues, possible causes, and how to solve them. Issue Possible cause Solution The receiver does not turn on. External power is too low. Check the charge on the external battery, and check the fuse if applicable. Internal power is too low. Check the charge on the internal battery. External power is not properly Check that the Lemo connector or connected.
Troubleshooting F Issue Possible cause Solution Receiver does not log data. Insufficient memory. Delete old files by holding down for 30 seconds. Delete the old files by using the delete and purge functions available in the Data Logging menu (see page 85) of the web interface. Data Logging option is disabled. Order the data logging option from your local Trimble dealer. Data logging is disabled as standard on all SPS GPS receivers.
F Troubleshooting Issue Possible cause Solution The base station receiver is not broadcasting. Port settings between reference receiver and radio are incorrect. Using the SCS900 software, connect to the reference radio through the receiver. If no connection is made, connect directly to the radio and change the port settings. Try to connect through the receiver again to ensure that they are communicating. Corrections are routed to a port rather than to the internal radio modem.
Troubleshooting Issue Possible cause Solution Roving receiver is not receiving radio. The base station receiver is not broadcasting. See page 160. F Incorrect over air baud rates Connect to the roving receiver’s between reference and rover. radio and make sure that it has the same setting as the reference receiver. The SCS900 software automatically configures the over-the-air baud rate to 9600.
F 1 62 Troubleshooting SPSx50 Modular GPS Receiver User Guide
Glossary This section explains some of the terms used in this manual. almanac A file that contains orbit information on all the satellites, clock corrections, and atmospheric delay parameters. The almanac is transmitted by a GPS satellite to a GPS receiver, where it facilitates rapid acquisition of GPS signals when you start collecting data, or when you have lost track of satellites and are trying to regain GPS signals. The orbit information is a subset of the emphemeris / ephemerides data.
Glossary datum Also called geodetic datum. A mathematical model designed to best fit the geoid, defined by the relationship between an ellipsoid and a point on the topographic surface established as the origin of the datum. World geodetic datums are typically defined by the size and shape of an ellipsoid and the relationship between the center of the ellipsoid and the center of the earth.
Glossary ellipsoid An ellipsoid is the three-dimensional shape that is used as the basis for mathematically modeling the earth’s surface. The ellipsoid is defined by the lengths of the minor and major axes. The earth’s minor axis is the polar axis and the major axis is the equatorial axis. emphemeris / ephemerides A list of predicted (accurate) positions or locations of satellites as a function of time. A set of numerical parameters that can be used to determine a satellite’s position.
Glossary (MTSAT Satellite-Based Augmentation System) MSAS A satellite-based augmentation system (SBAS) that provides a free-to-air differential correction service for GPS. MSAS is the Japanese equivalent of WAAS, which is available in the United States. MTSAT SatelliteSee MSAS. Based Augmentation System multipath Interference similar to ghosts on a television screen that occurs when GPS signals arrive at an antenna having traversed different paths.
Glossary real-time differential Also known as real-time differential correction, DGPS. GPS Real-time differential GPS is the process of correcting GPS data as you collect it. This is achieved by having corrections calculated at a base station sent to the receiver via a radio link. As the rover receives the position it applies the corrections to give you a very accurate position in the field. Most real-time differential correction methods apply corrections to code phase positions.
Glossary (Virtual Reference Station) VRS A VRS system consists of GPS hardware, software, and communication links. It uses data from a network of base stations to provide corrections to each rover that are more accurate than corrections from a single base station. To start using VRS corrections, the rover sends its position to the VRS server. The VRS server uses the base station data to model systematic errors (such as ionospheric noise) at the rover position.
