Acronym List

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