Novatel OM-20000077 user manual Satellite-Based Augmentation System Sbas

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Positioning Modes of Operation

Chapter 6

 

 

 

OCXO, and so on).

Multipath Signal Reception – Multipath signal reception can potentially cause large pseudorange and carrier phase measurement biases. Multipath conditions are very much a function of specific antenna site location versus local geography and man-made structural influences. Severe multipath conditions could skew range measurements by as much as 100 meters or more.

6.2Satellite-Based Augmentation System (SBAS)

A Satellite-Based Augmentation System (SBAS) is a type of geo-stationary satellite system that improves the accuracy, integrity, and availability of the basic GPS signals. Accuracy is enhanced through the use of wide area corrections for GPS satellite orbits and ionospheric errors. Integrity is enhanced by the SBAS network quickly detecting satellite signal errors and sending alerts to receivers to not use the failed satellite. Availability is improved by providing an additional ranging signal to each SBAS geostationary satellite.

SBAS includes the Wide-Area Augmentation System (WAAS), the European Geo-Stationary Navigation System (EGNOS), and the MTSAT Satellite-Based Augmentation System (MSAS). At the time of publication, there are two WAAS satellites over the western Atlantic Ocean and the Pacific (PRN 122 and PRN 134 respectively) and one EGNOS satellite over the eastern Atlantic Ocean (PRN 120). SBAS data is available from any of these satellites and more satellites will be available in the future.

The primary functions of SBAS include:

data collection

determining ionospheric corrections

determining satellite orbits

determining satellite clock corrections

determining satellite integrity

independent data verification

SBAS message broadcast and ranging

system operations & maintenance

As shown in Figure 7, The SBAS Concept, the SBAS is made up of a series of Reference Stations, Master Stations, Ground Uplink Stations and Geostationary Satellites (GEOs). The Reference Stations, which are geographically distributed, pick up GPS satellite data and route it to the Master Stations where wide area corrections are generated. These corrections are sent to the Ground Uplink Stations which up-link them to the GEOs for re-transmission on the GPS L1 frequency. These GEOs transmit signals which carry accuracy and integrity messages, and which also provide additional ranging signals for added availability, continuity and accuracy. These GEO signals are available over a wide area and can be received and processed by L1 GPS receivers with appropriate firmware. GPS user receivers are thus able to receive SBAS data in-band and use not only differential corrections, but also integrity, residual errors and ionospheric information for each monitored satellite.

The signal broadcast through the SBAS GEOs to the SBAS users is designed to minimize modifications to standard GPS receivers. As such, the GPS L1 frequency (1575.42 MHz) is used, together with GPS-type modulation - e.g. a Coarse/Acquisition (C/A) pseudorandom (PRN) code. In addition, the code phase timing is

SUPERSTAR II User Manual Rev 3

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Contents Superstar Proprietary Notice Table of Contents Appendices Tables Figures Software License Software License Contact Information Firmware UpdatesElectrostatic Discharge CE Notice Warranty Policy Congratulations Scope Related PublicationsRelated Publications Superstar II GPS Card IntroductionIntroduction Chapter FlexPak-SSIIChapter Introduction Radio Frequency RF Section Receiver SpecificationsPhysical Characteristics System ArchitectureGPS Antenna Enclosure and Wiring HarnessPrincipal Power Supply Optional LNA Power SupplyTypical System Configuration Reference Description InstallationSerial Connection Chapter InstallationElectrostatic Discharge Equipment InterconnectionAntenna Location Installation ConsiderationsPower Connection Installation ChapterBase Station and Rover Units Separation Connectors and Connector Pins Assignment1 J1 Interface and Power Connector Data LinkSerial Data Interface RF Connector J2RF Input Preamplifier Power Pass-Through Antenna SupplyProtocol Selection and Non Volatile Memory Memory Back-UpDiscretes IP2 and IP3 functions Use of DiscretesDefault Configuration Non Volatile MemoryNon-Volatile Memory Data Description Reference Installation OverviewOperation Typical Operational Configuration Reference DescriptionOperation Chapter Serial Port Default SettingsCommunications with the Receiver Getting StartedChapter Operation Power-Up InformationBoot Information Operational InformationConfigurable Parameters Data RequestsReceiver States Self-Test Mode Built-In Status Tests Dead-Reckoning ModeDatum Support Message Formats RTCM-Format MessagesRTCM1 Differential GPS Corrections Fixed RTCM2 Delta Differential GPS Corrections Fixed RTCM9 Partial Satellite Set Differential CorrectionsChapter Message Formats Message Formats Chapter Nmea Format Data MessagesGPS System Errors Positioning Modes of OperationSingle-Point or Autonomous Positioning Modes of Operation Chapter Satellite-Based Augmentation System SbasSbas Receiver Sbas MessagesChapter Positioning Modes of Operation Positioning Modes of Operation Chapter Cable Lengths Vs. Gain TroubleshootingTroubleshooting Chapter Technical Specifications Appendix aSuperstar II Family Performance Output Messages Technical Specifications Appendix aMechanical Drawing Appendix a Technical SpecificationsJ1 Interfaces and Power Connector Pin Assignment Connector Pin AssignmentO Signals Voltage Limits 3 I/O Electrical CharacteristicsAppendix B FlexPak-SSII SpecificationsPort Pin-Outs Status IndicatorsAppendix B FlexPak-SSII Specifications FlexPak Status IndicatorsFlexPak-SSII Specifications Appendix B Automobile Power Adapter Cable NovAtel part numberCables FlexPak 13-Pin Serial Cable 3.2 13-Pin Deutsch to DB9 Serial Cable NovAtel part numberDescription Setup and OperationNormal Setup Development KitDifferential GPS Setup Dgps Setup with the FlexPak-SSIIStarView Software Installation Cable Selection Antenna SpecificationsCoaxial Cable Specifications Appendix CTypical Current Consumption Versus Antenna Gain Antenna Specifications Appendix CGeodetic Active Antenna Antenna Gain Depending on Cable Length RequiredRecommended Geodetic Active Antennas Appendix C Antenna SpecificationsActive Antenna Passive AntennaGPS Antenna 201-990146-716 MCX, +12 dB Passive Antenna Specifications Patch ElementGPS Antenna 201-990147-606 +26 dB Antenna Specifications Appendix C Standards/References Appendix DRe-Acquisition Appendix ETtff and Satellite Acquisition Time-To-First-Fix TtffSystem Requirements Utility InstallationAppendix F Updating Receiver FirmwareStarting Software and Options Update Registration Key AcceptedUpdating Receiver Firmware Appendix F Appendix F Updating Receiver Firmware Programming SuccessSpace Segment Appendix GGPS Overview GPS System DesignAppendix G GPS Overview Height RelationshipsControl Segment User SegmentGPS Overview Appendix G GPS PositioningAccuracy versus Precision1 Single-Point vs. Relative PositioningMultipath Static vs. Kinematic PositioningReal-time vs. Post-mission Data Processing Consequences of Multipath Reception Why Does Multipath Occur?Antenna Site Selection Hardware Solutions For Multipath ReductionAntenna Designs GPS Signal Multipath vs. Increased Antenna HeightGPS Overview Appendix G Glossary of Terms Appendix HGlossary of Terms Appendix H Appendix H Glossary of Terms Glossary of Terms Appendix H Acronyms AppendixAcronyms Appendix Appendix Acronyms Index Index GEO, SbasIndex Index OM-20000077 Rev 2004/03/11