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| Also manufacturered as:
|
| A/S Anti-Spoofing |
| AAIM Airborne Autonomous Integrity Monitoring |
| ABAS Aircraft Based Augmentation Systems |
| ACAC Arab Civil Aviation Commission |
| ACF Auto-Correlation Function |
| ADAS Advanced Driving Assistance Systems |
| ADC Analog to Digital Converter |
| ADS-B Automatic Dependent Surveillance-Broadcast |
| AEP Architecture Evolution Plan |
| AF U.S. Air Force |
| AFCAC African Civil Aviation Commission |
| AFI Africa-Indian Ocean |
| AGC Automatic Gain Control |
| AHRS Attitude and Heading Reference Systems |
| AIS Automatic Identification System |
| AIV Assembly |
| AL Alert Limit |
| AltBOC Alternative BOC |
| AM Amplitude Modulation |
| AMCS Alternate Master Control Station |
| ANSP Air Navigation Service Provider |
| ANTEX ANtenna EXchange format |
| AOA Airport Operators Association |
| AOA Angle Of Arrival |
| AOAD/M T Allen Osborne Associates Dorne Margolin Model T |
| AOC Advanced Operational Capability |
| AOCS Attitude and Orbit Control Subsystem |
| AOR Atlantic Ocean Region |
| AP Access Point |
| AP Application Protocol |
| APC Antenna Phase Centre |
| APEC Asia Pacific Economic Cooperation |
| API Application Programming Interface |
| APIRG AFI Planning and Implementation Regional Group |
| APPS Automatic Precise Positioning Service |
| APV Approach oPerations with Vertical guidance |
| APVI Approach oPerations with Vertical guidance I |
| APVII Approach oPerations with Vertical guidance II |
| AR Axial Ratio |
| ARAIM Advanced RAIM |
| ARNS Aeronautical Radio Navigation Service |
| ARP Antenna Reference Point |
| ARPA Automatic Radar Plotting Aids |
| AS Anti-Spoofing |
| ASBC Advanced Space Business Corporation |
| ASECNA from french: Agence pour la Securite de la Navigation Aerienne en Afrique et |
| ASICs Applications Secific Integrated Circuit |
| ASN.1 Abstract Syntax Notation 1 |
| ASQF Application Specific Qualification Facility |
| ASZ Autocorrelation Side-lobe Zero |
| ATC Air Traffic Control |
| ATM Automated Teller Machine |
| ATM Air Traffic Management |
| ATV Automated Transfer Vehicle |
| AUC African Union Commission |
| AWGN Additive White Gaussian Noise |
| AWOP All Weather Operations Panel |
| BC Before Christ |
| BCS Binary Coded Symbols |
| BDT BeiDou Time |
| BI Behavioral Interventions |
| BIE Bureau International de l'Heure |
| BIH From French: Bureau International de l'Heure |
| BIPM Bureau International des Poids et Mesures |
| BLUE Best Linear Unbiased Minimum-Variance Estimator |
| BM Benchmark |
| BMCS Backup Master Control Station |
| BOC Binary Offset Carrier |
| BPSK Binary Shift Phase Keying |
| BRS Baricentric Reference System |
| C/A Coarse/Acquisition |
| C/NAV Commercial Navigation Message |
| CAASD Center for Advanced Aviation System Development (MITRE) |
| CAES Computer Aided Earthmoving System |
| CAN Controller Area Network |
| CAR Caribbean and South American region |
| CARERI Chinese Aeronautical Radio Electronics Research Institute |
| CASM Coherent Adaptive Sub-Carrier Modulation |
| CBCS Composite Binary Coded Symbols |
| CBOC Composite BOC |
| CCF Central Control Facility |
| CCZ Congestion Charge Zone |
| CDCM Coastal Defense Cruise Missile |
| CDDIS Crustal Dynamics Data Information System |
| CDDS Commercial Data Distribution Service |
| CDMA Code Division Multiple Access |
| CDTI Cockpit Display of Traffic Information |
| CEP Conventional Ephemeris Pole |
| CEP Circular Error Probable |
| CF Compact Flash |
| CFSP Common Foreign and Security Policy |
| CGCS2000 China Geodetic Coordinate System 2000 |
| CGSIC Civil GPS Service Interface Committee |
| CHA Channel of High Accuracy |
| CHAMP CHAllenging Minisatellite Payload |
| CHARS Customer Hierarchy And Reporting System |
| CIO Conventional International Origin |
| CIP Celestial Intermediate Pole |
| CIR Cascading Integer Resolution |
| CIS Conventional Inertial System |
| CL Civil Long |
| CM Civil Moderate |
| CMCF Central Monitoring and Control Facility |
| CMR Compact Measurement Record |
| CMSA Cruise Missile Support Activity |
| CNAV Civil NAVigation message |
| CNS Communication Navigation Surveillance |
| CNSS Compass Navigation Satellite System |
| COCESNA Corporacion Centroamerica de Servicios de Navegacion Aerea |
| CODE Centre for Orbit Determination in Europe |
| CONUS CONtinental United States |
| CORS Continuously Operating Reference Stations |
| COSMIC Constellation Observing System for Meteorology |
| CP Circular Polarization |
| CPF Central Processing Facility |
| CPFPS Central Processing Facility Processing Set |
| CPN Coloured Petri Nets |
| CPU Central Processing Unit |
| CR Council Resolution |
| CRC Cyclic Redundancy Check |
| CRF Celestial Reference Frame |
| CRLB Cramer Rao Lower Bound |
| CRS Conventional Celestial Reference System |
| CRT Cathode Ray Tube |
| CS Commercial Service |
| CSA Channel of Standard Accuracy |
| CSIM Constellation Simulator |
| CSK Code Shift Keying |
| CSRS Canadian Spatial Reference System |
| CTP Conventional Terrestrial Pole |
| CTS Conventional Terrestrial System |
| CW Continuous Wave |
| CWAAS Canadian WAAS |
| DAB Digital Audio Broadcasting |
| DAC Digital-to-Analog Converters |
| DASS Distress Alerting Satellite System |
| DCB Differential Code Biases |
| DDMA Doppler Division Multiple Access |
| DEOS Delft Institute of Earth Observation and Space Systems |
| DF Dual Frequency |
| DGNSS Differential GNSS |
| DGPS Differential GPS |
| DGRS DGPS Reference Station |
| DH Decision Height |
| DLL Delay Lock Loop |
| DME Distance Measuring Equipment |
| DoD US Department of Defense |
| DOP Dilution Of Precision |
| DOT Department Of Transportation |
| DoY Day-of-Year |
| DP Dot Product |
| DSCS Defense Satellite Communications System |
| DSNS Differential Satellite Navigation Systems |
| DSP Digital Signal Processor |
| DSPN Direct Sequence Pseudo Noise |
| DSRC Dedicated Short-Range Communications |
| DSSS Direct Sequence Spread Spectrum |
| DVP Development and Verification Platform |
| EASA European Aviation Safety Agency |
| EC European Commission |
| ECA Error Characterization Approach |
| ECAC European Civil Aviation Conference |
| ECAM Electronic Centralised Aircraft Monitor |
| ECEF Earth Centred Earth Fixed |
| ECI Earth Centred Inertial |
| ECMWF European Centre for Medium-Range Weather Forecasts |
| EDAS EGNOS Data Access System |
| EDS EGNOS Data Server |
| EEGS EGNOS Extension to Eastern Europe |
| EETS European Electronic Tolling Service |
| EFC Electronic Fee Collection |
| EFIS Electronic Flight Instrument System |
| EGNOS European Geostationary Navigation Overlay System |
| EICAS Engine Indications and Crew Alerting System |
| EIRP Effective Isotropic Radiated Power |
| E-L Early-Late |
| ELT Emergency Location Terminal |
| EMLP Early Minus Late Power |
| EMP Electro-Magnetic Pulse |
| EMR Energy Mines and Resources |
| EMT Effective Monitor Threshold |
| ENC European Navigation Conference |
| ENT EGNOS Network Time |
| ENU East North Up |
| EOL End-Of-Life |
| EOP Earth Orientation Parameters |
| EPFS Electronic Position Fixing System |
| EPIRB Emergency Position Indicating Radio Beacons |
| EPPP Enhanced Precise Point Positioning |
| ERIS External Regional Integrity Services |
| ERP Earth Rotation Parameters |
| ERTMS European Rail Traffic Management System |
| ESA European Space Agency |
| ESDP European Security and Defence Policy |
| ESOC European Space Operations Centre |
| ESSP European Satellite Service Provider |
| ESTB EGNOS Test Bed |
| ET Ephemeris Time |
| ETA Estimated Time of Arrival |
| ETC Electronic Tolling Collection |
| ETCS European Train Control System |
| ETML European Traffic Management Layer |
| ETSO European Technical Standard Order |
| EU European Union |
| EuCAP European Conference on Antennas and Propagation |
| EWAN EGNOS Wide Area Network |
| F/NAV Freely accessible Navigation Message |
| FAA Federal Aviation Administration |
| FAS Final Approach Segments |
| FDE Fault Detection and Exclusion |
| FDF Flight Dynamics Facility |
| FDMA Frequency Division Multiple Access |
| FEC Forward Error Correction |
| FH Faded-Harmonics |
| FIR Flight Information Region |
| FIR Finite Impulse Response |
| FKP From German: Flaechen Korrektur Parameter |
| FLL Frequency Lock Loop |
| FM Frequency Modulation |
| FMS Flight Management System |
| FOC Full Operational Capability |
| FOP Final Operational Phase |
| FPGA Field Programmable Gate Array |
| F-PPP Fast Precise Point Positioning |
| FTP File Transfer Protocol |
| G/NAV Governmental Navigation Message |
| GA Ground Antennas |
| GACF Ground Assets Control Facility |
| GADEROS Galileo Demonstrator for Railway Operation System |
| gAGE Research group of Astronomy and GEomatics |
| GAST Greenwich Apparent Sidereal Time |
| GBAS Ground-Based Augmentation System |
| GCC Ground Control Centres |
| GCS Ground Control Segment |
| GDOP Geometric Dilution Of Precision |
| GEAS GNSS Evolutionary Architecture Study |
| GEO Geostationary Orbit |
| GESS Galileo Experimental Sensor Stations |
| GGSP Galileo Geodetic Service Provider |
| GIC GNSS/Ground Integrity Channel |
| GIM Global Ionospheric Maps |
| GIOVE Galileo In-Orbit Validation Element |
| GIS Geographic Information System |
| GIT GNSS Implementation Team |
| GIVD Grid Ionospheric Vertical Delay |
| GIVE Grid Ionospheric Vertical Error |
| GIVEI GIVE Indicators |
| GJU Galileo Joint Undertaking |
| GLA General Lighthouse Authorities |
| GLONASS GLObal NAvigation Satellite System |
| GLONASST GLONASS Time |
| GLP Good Laboratory Practice |
| GLS GNSS Landing System |
| GMDSS Global Maritime Distress and Safety System |
| GMS Ground Mission Segment |
| GMSK Gaussian Minimum Shift Keying |
| GMST Greenwich Mean Sidereal Time |
| GMT Greenwich Mean Time |
| GNS Global Navigation System |
| GNSS Global Navigation Satellite System |
| GNSSP GNSS Panel |
| GOC Galileo Operating Company |
| GPRS General Packet Radio Service |
| GPS Global Positioning System |
| GPS/MET Global Positioning System/Meteorology |
| GPSOC GPS Operations Center |
| GPST GPS Time |
| GPSW GPS Wing |
| GRACE Gravity Recovery And Climate Experiment |
| GRAPHIC Group and Phase Ionospheric Calibration |
| GRAS Ground-based Regional Augmentation System |
| GRS Geodetic Reference System |
| GRSP Galileo Geodetic Reference Service Provider |
| GSA European GNSS Agency |
| GSLV Geosynchronous Satellite Launch Vehicle |
| GSM Global System for Mobile communication |
| GSO Geostationary Satellites Orbit |
| GSS Galileo Sensor Stations |
| GST Galileo System Time |
| GTRF Galileo Terrestrial Reference Frame |
| GUS Ground Uplink Stations |
| HAL Horizontal Alert Limit |
| HD Hydrostatic Delay |
| HD Hard Disk |
| HDOP Horizontal Dilution Of Precision |
| HEO Highly Elliptical Orbit |
| HF High Frequency |
| HIS High Integrity Service |
| HMI Hazardous Misleading Information |
| HP High Precision |
| HPA High Power Amplifier |
| HPE Horizontal Position Error |
| HPL Horizontal Protection Level |
| HPPS High Precision Positioning Service |
| HPS High Precision Service |
| HTML Hyper Text Markup Language |
| I/NAV Integrity Navigation Message |
| IAEA International Atomic Energy Agency |
| IAG International Association of Geodesy |
| IAS Institut Aero Spatial |
| IAU International Astronomical Union |
| IBPL Isotropy Based Protection Level |
| IBS Integrated Bridge Systems |
| IC Integrated Chips |
| ICAO International Civil Aviation Organization |
| ICC Institut Cartografic de Catalunya |
| ICD Interface Control Document |
| ICG International Committee on Global Navigation Satellite Systems |
| ICR Isotropic Confidence Ratio |
| ICRF International Celestial Reference Frame |
| ICRS International Celestial Reference System |
| ICS Internal Communication Subsystem |
| IDF Ionospheric Disturbance Flag |
| IEP Initial Experimental Phase |
| IERS International Earth Rotation and Reference Systems Service |
| IF Intermediate Frequencies |
| IGEX International GLONASS EXperiment |
| IGP Ionospheric Grid Point |
| IGS International GNSS Service |
| IGSO Inclined Geo-Synchronous Orbit |
| ILRS IRNSS Laser Ranging Station |
| ILS Instrument Landing Systems |
| IM Inter Modulation |
| IMO International Maritime Organization |
| IMU Inertial Measurement Unit |
| INC IRNSS Navigation Centre |
| INLUS Indian Land Uplink Station |
| INMCC Indian Master Control Center |
| INRES Indian REference Stations |
| INS Inertial Navigation System |
| IOC Initial Operational Capability |
| IOD Issues of Data |
| IODC Issue of Data Clock |
| IODE Issue Of Data Ephemeris |
| IODF Issue Of Data Fast Corrections |
| IODI Issue of Data IGP Mask |
| IODN Issue of Data Navigation |
| IODP Issue Of Data PRN mask |
| IODS Issue of Data Service Message |
| ION Institute Of Navigation |
| IONEX IONosphere map EXchange format |
| ION-NTM ION National Technical Meeting |
| IOR-W Indian Ocean Region West |
| IOT In-Orbit Test |
| IOV In-Orbit Validation |
| IP Internet Protocol |
| IPF Integrity Processing Facility |
| IPP Ionospheric Pierce Point |
| IRCDR IRNSS CDMA Ranging Stations |
| IRDCN IRNSS Data Communication Network |
| IRIMS IRNSS Range and Integrity Monitoring Stations |
| IRN Information Request Notice |
| IRNSS Indian Regional Navigational Satellite System |
| IRNWT IRNSS Timing Centre |
| IRTTC IRNSS TTC and Uplinking Stations |
| ISI Inter Symbol Interference |
| ISM Integrity Support Message |
| ISRO Indian Space Research Organization |
| ISS International Space Station |
| ITR International Terrestrial Reference |
| ITRF International Terrestrial Reference Frame |
| ITRS International Terrestrial Reference System |
| ITU International Telecommunications Union |
| ITU-R International Telecommunications Union Radiocommunication Sector |
| IWG Interoperability Working Group |
| JAXA Japan Aerospace Exploration Agency |
| JD Julian Day |
| JLOC Jammer Location |
| JMA Japan Meteorological Agency |
| JPL Jet Propulsion Laboratory |
| KH Kelvin-Helmholtz |
| KMF Key Management Facility |
| L2CL L2 Civil Long |
| L2CM L2 Civil Moderate |
| LAAS Local Area Augmentation System |
| LAST Local Apparent Sidereal Time |
| LBS Location Based Services |
| LCA Liability Critical Applications |
| LCD Liquid Crystal Display |
| LEO Low Earth Orbit |
| LEOP Launch Early OPerations |
| LEX Michibiki experimental signal |
| LFSR Linear Feedback Shift Registers |
| LHCP Left Hand Circular Polarization |
| LM Local Mean |
| LMST Local Mean Sidereal Time |
| LNA Low Noise Amplifier |
| LNAV Lateral Navigation |
| LO Local Oscillator |
| LOC Linear Offset Carrier |
| LOS Line-Of-Sight |
| LP Localizer Performance |
| LPV Localizer Performance with Vertical guidance |
| LRIT Long Range Identification and Tracking |
| LT Long Term |
| LVP Low Visibility Procedures |
| MASPS Minimum Aviation System Performance Standards |
| MBOC The Multiplexed Binary Offset Carrier |
| MCC Mission Control Centers |
| MCS Master Control Station |
| MCS Multilevel Coded Spreading Symbols |
| MEAG Mission Evolution Advisory Group |
| MEDLL Multipath Estimating Delay Lock Loop |
| MEH Marine Electronic Highway |
| MEO Medium Earth Orbit |
| MEOSAR Medium Earth Orbit Search And Rescue |
| METIS Mediterranean Introduction of GNSS Services |
| MGF Message Generation Facility |
| MHSS Multiple Hypothesis Solution Separation |
| MI Misleading Information |
| MJD Modified Julian Day |
| MLS Microwave Landing System |
| MLU MRS Land User service |
| MM Monument Marker |
| MMI Man Machine Interface |
| MMSSS Multi-Mode Spread-Spectrum Sub-carrier Modulation |
| MNAV Military NAVigation Message |
| MOB Man Overboard |
| MODIP MOdified DIP latitude |
| MOPS Minimum Operational Performance Specification |
| MPR MultiPath Ratio |
| MPSK Multiple Phase Shift Keying |
| MRA Measurement Rejection Approach |
| MRS Multi-Constellation Regional System |
| MS Monitor Stations |
| MSAS MTSAT Satellite Augmentation System |
| MSC Mobile Satellite Communications |
| MSD Minimum Set of Data |
| MSE Mean-Square Error |
| MSF Mission Support Facility |
| MSI Misleading Signal-in-Space Information |
| MSK Minimum Shift Keying |
| MSTID Medium Scale Traveling Ionospheric Disturbances |
| MT Military Tracking |
| MT Message Type |
| MT0 Message Type 0 |
| MT1 Message Type 1 |
| MT2 Message Type 2 |
| MT3 Message Type 3 |
| MT4 Message Type 4 |
| MT5 Message Type 5 |
| MTPF Maintenance and Training Platform |
| MTSAT Multifunctional Transport Satellite |
| MUCF Mission Uplink Control Facility |
| NAD83 North American Datum of 1983 |
| NANUs Notice Advisory to Navstar Users |
| NAPEOS Navigation Package for Earth Observation Satellites |
| NAS National Airspace System |
| NASA National Aeronautics and Space Administration |
| NAV Navigation Message |
| NAVCEN NAVigation CENter |
| NCA Non-Critical applications |
| NCO Numerical Control Oscillators |
| NDB Non-Directional Beacon |
| NDGPS Nationwide Differential Global Positioning System |
| NELP Non-coherent Early minus Late Power |
| NEU North-East-Up |
| NGA National Geospatial-Intelligency Agency |
| NIST National Institute of Standards and Technology |
| NLES Navigation Land Earth Stations |
| NLOS Non Line Of Sight |
| NMCS New Master Control Station |
| NMEA National Marine Electronics Association |
| NOCC National Operations Control Center |
| NOTAM NOTice to AirMen |
| NPA Non-Precision Approach |
| NPV Non Precision Approach with vertical guidance |
| NRTK Network RTK |
| NRZ Non-Return to Zero |
| NSE Navigation System Error |
| NSP Navigation System Panel |
| NSU Navigation Signal generator Unit |
| NSV Near Space Vehicle |
| NTRIP Networked Transport of RTCM via Internet Protocol |
| OA Operational Advisories |
| OBD On-Board diagnostics |
| OBU On Board Unit |
| OCC Operational Control Centers |
| OCS Operational Control System |
| OCX Operational Control Segment |
| OD&TS Orbit Determination and Time Synchronisation |
| ODTS Orbit Determination and Time Synchronisation |
| OEM Original Equipment Manufacturer |
| OLAF from French: Office de Lutte Anti-Fraude |
| ONCE Spanish organisation for the blind |
| OPF Operations Preparation Facility |
| OQPSK Offset QPSK |
| ORMS Orbiter and Radio Metric Systems |
| OS Open Service |
| OS Operative System |
| OSD Open Signal Data |
| OSP Open Signal Pilot |
| OSPF Orbit determination and Synchronization Processing Facility |
| OTF On-The-Fly |
| PA Precision Approach |
| PACF Performance Assessment and Checkout Facility |
| PANS Procedures for Air Navigation Services |
| PAYD Pay-As-You-Drive |
| PBN Performance-Based Navigation |
| PCV Phase Centre Variations |
| PDA Personal Digital Assistant |
| PDF Portable Document Format |
| PDM Position Domain Monitoring |
| PDOP Position Dilution Of Precision |
| PE Protection Error |
| PFD Primary Flight Display |
| PL Protection Level |
| PLANS Position Location and Navigation Symposium |
| PLL Phase Lock Loop |
| PM Phase Modulation |
| PND Portable Navigation Devices |
| PNG Portable Network Graphics |
| PNT Positioning |
| POD Precise Orbit Determination |
| POI Point Of Interest |
| PPP Precise Point Positioning |
| PPS Precise Point Service |
| PR Pseudo Random |
| PRN Pseudo-Random Noise |
| PRS Public Regulated Service |
| PRTODTS Precise Real Time Orbit Determination and Time Synchronization |
| PS Precision Service |
| PSD Power Spectral Density |
| PSK Phase-Shift Keying |
| PSTD Pseudospectral Time-Domain |
| PTC Positive Train Control |
| PTF Precision Timing Facility |
| PTP Point-To-Point |
| PVT Position |
| PZ-90 Parametry Zemli 1990 (Parameters of the Earth 1990) |
| QOS Quality Of Service |
| QPSK Quadrature Phase-Shift Keying |
| QPSM Quadrature Product Sub-carrier Modulation |
| QZSS Quasi-Zenith Satellite System |
| RAAN Right Ascension of the Ascending Node |
| RAIM Receiver Autonomous Integrity Monitoring |
| RC Rased Cosine |
| RCF Raised Cosine Filter |
| RDS Radio Data System |
| RDSS Radio Determination Satellite Service |
| RECs Regional Economic Communities |
| RF Radio Frequency |
| RFC Radio Frequency Compatibility |
| RFI Radio Frequency Interference |
| RFID Radio-Frequency Identification |
| RHCP Right Hand Circular Polarization |
| RICS Royal Institution of Chartered Surveyors |
| RIMS Ranging Integrity Monitoring Stations |
| RINEX Receiver INdependent EXchange format |
| RK4 4th order Runge-Kutta |
| RMS Root Mean Square |
| RNAV aRea NAVigation |
| RNP Required Navigation Performance |
| RNSS Radionavigation Satellite System |
| RRAIM Relative RAIM |
| RRC Range Rate Corrections |
| RRC Root Raised Cosine |
| RSA Russian Space Agency |
| RSIM Reference Stations and Integrity Monitors |
| RSN Reference Stations Network |
| RTCM Radio Technical Commission for Maritime Services |
| RTK Real-Time Kinematics |
| RUC Road User Charging |
| RX Receiver |
| S/A Selective Availability |
| SA Select Availability |
| SACCSA From Spanish: Soluci |
| SAIF Submeter-class Augmentation with Integrity Function |
| SAM South America Region |
| SAR Search and Rescue |
| SARPs Standard and Recommended Practices |
| SBAS Satellite-Based Augmentation System |
| SBCS Sinusoidal Binary Coded Symbols |
| SCA Safety Critical Applications |
| SCC System Control Centre |
| SCC Spacecraft Control Centre |
| SCCF Spacecraft and Constellation Control Facility |
| SCPF Spacecraft and Constellation Planning Facility |
| SDA System Design Approval |
| SDCM System of Differentional Correction and Monitoring |
| SDD Service Definition Document |
| SDR Software Defined Radio |
| SEP Spherical Error Probable |
| SF Single Frequency |
| SGLS Space Ground Link Subsystem |
| SI International System of Physical Units |
| SINEX Solution (Software/technique) INdependent EXchange format |
| SIS Signal In Space |
| SISA Signal-in-Space Accuracy |
| SISE SIS Error |
| SISMA SIS Monitoring Accuracy |
| SLR Satellite Laser Ranging Station |
| SMCS Sinusoidal Multilevel Coded Symbol |
| SMS Short Message Service |
| SNAS Satellite Navigation Augmentation System |
| SNIR Signal to Noise plus Interference Ratio |
| SNR Signal to Noise Ratio |
| SNT SBAS Network Time |
| SOC Sinusoidal Binary Offset Carrier |
| SoL Safety-of-Life |
| SOLAS Safety of Life at Sea |
| SOTDMA Self-Organizing Time Division Multiple Access |
| SP Service Provider |
| SP3 Standard Product #3 |
| SPAC Satellite Positioning Research and Application Center |
| SPD Slant Path Delay |
| SPEED Support Platform for EGNOS Evolutions and Demonstrations |
| SPF Service Product Facility |
| SPP Standard Point Positioning |
| SPS Standard Positioning Service |
| SQM Signal Quality Monitoring |
| SRD System Requirement Document |
| SRIF Square-Root Information Filtering |
| SRRC Square-Root Raised Cosine |
| SS Spread Spectrum |
| SSC Spectral Separation Coefficient |
| SSEG Space Segment |
| SSTL Surrey Satellite Technology Ltd. |
| ST Short Term |
| STC aircraft Supplemental Type Certificates |
| STEC Slant Total Electron Content |
| STF Signal Task Force |
| SU Soviet Union |
| SUPPs regional SUPplementary Procedures |
| SV Space Vehicle |
| SVN Space Vehicle Number |
| SW Synchronization Words |
| SW Software |
| TACAN TACtical Air Navigation |
| TAI From French: Temps Atomique International |
| TBD see TCB |
| TCA Terminal Control Area |
| TCAR Three-Carrier Ambiguity Resolution |
| TCAS Traffic Collision Avoidance System |
| TCB from French: Temps Coordonnee Barycentrique |
| TCG from French: Temps Coordonnee Geocentrique |
| TDARDS Truth Data Acquisition |
| TDB from French: Temps Dinamique Barycentrique |
| TDOP Time Dilution Of Precision |
| TDS Technology Demonstration System |
| TDT Terrestrial Dynamic Time |
| TEC Total Electron Content |
| TECU Total Electron Content Unit |
| TGD Total Group Delay |
| TLM TeLeMetry |
| TLS Target Level of Safety |
| TMBOC Time-Multiplexed BOC |
| TMR Triple Modular Redundancy |
| TOW Time Of Week |
| TRF Terrestrial Reference Frame |
| TRS Conventional Terrestrial Reference System |
| TS Time Synchronisation |
| TSO Technical Standard Order |
| TT Terrestrial Time |
| TT&C Telemetry |
| TTA Time-To-Alert |
| TTC Telemetry |
| TTFF Time To First Fix |
| TUS Test User Segment |
| TV Television |
| TX Transmitter |
| U.S. United States |
| UAV Unmanned Aerial Vehicle |
| UCAR University Corporation of Atmospheric Research |
| UDRE User Differential Range Error |
| UDREI UDRE Indicator |
| UEN Up-East-North |
| UERE User Equivalent Range Error |
| UIRE User Ionospheric Range Error |
| UK United Kingdom |
| ULS Mission Uplink Stations |
| UMTS Universal Mobile Telecommunications System |
| UNB University of New Brunswick |
| UNE Up North East |
| UNECA United Nations Economic Commission for Africa |
| UNISPACE United Nations Conference on the Exploration and Peaceful Uses of Outer Space |
| UPC Technical University of Catalonia |
| URA User Range Accuracy |
| URE User Range Error |
| US United States |
| USA United States of America |
| USB Universal Serial Bus |
| USCG U.S. Coast Guard |
| USNDS US Nuclear Detonation (NuDet) Detection System |
| USNO United States Naval Observatory |
| UT Universal Time |
| UT0 Universal Time 0 |
| UT1 Universal Time 1 |
| UT2 Universal Time 2 |
| UTC Universal Time Coordinated |
| UV Ultra Violet |
| VAL Vertical Alert Limit |
| VDB VHF Data Broadcast |
| VDLL Vector DLL |
| VDOP Vertical Dilution Of Precision |
| VE Very Early |
| VHF Very High Frequency |
| VL Very Late |
| VLBI Very Long Baseline Interferometry |
| VNAV Vertical Navigation |
| VOR VHF Omnidirectional Range |
| VPE Vertical Position Error |
| VPL Vertical Protection Level |
| VRS Virtual Reference Station |
| VTS Vessel Traffic Service |
| WAAS Wide Area Augmentation System |
| WAD Wide Area Differential |
| WADGPS Wide Area Differential GPS |
| WAGE Wide Area GPS Enhancements |
| WAN Wide Area Network |
| WAP Wireless Application Protocol |
| WARTK Wide Area Real-Time Kinematics |
| WARTK-EGAL Wide Area Real-Time Kinematics based on EGNOS and Galileo |
| WG World Geodetic |
| WG Working Group |
| WGS World Geodetic System |
| WGS84 World Geodetic System 84 |
| WLS Weighted Least Square |
| WMS WAAS Master Station |
| WRC World Radio Conference |
| WRS Wide-area Reference Stations |
| XPE Vertical/ Horizontal Protection Error |
| XPL Vertical/ Horizontal Protection Level |
| ZHD Zenith Hydrostatic Delay |
| ZPD Zenith Path Delay |
| ZTD Zenith Tropospheric Delay |
| ZWD Zenith Wet Delay |