This glossary serves as a reference for understanding the many abbreviations and terms used in geodesy. It is directly linked to related content across the website, ensuring an up-to-date and interconnected resource. Each glossary term automatically appears as a link wherever it is used on the site.
We aim to keep the glossary as comprehensive and accurate as possible. If you identify missing terms or would like to suggest updates or corrections, please feel free to contact us (website admin).
A
- A-GPS / A-GNSS - Assisted GPS/GNSS
- AAM - Atmospheric Angular Momentum
- Absolute Gravimetry
- Absolute positioning
- AC - Analysis Center
- ACC - Analysis Center Coordination / Coordinator
- Accuracy
- ADT - Absolute Dynamic Topography
- AFREF - African Reference Frame
- AGGO - Argentine-German Geodetic Observatory
- AGrav - Absolute Gravity Database
- AGU – American Geophysical Union (AGU)
- AIUB - Astronomical Institute, University of Bern, Switzerland
- Almanac
- Altimetry
- Ambiguity resolution
- AOC - Advanced Operational Capability
- APREF - Asia-Pacific Reference Frame
- AROF - Ambiguity Resolution On the Fly
- ARP - Antenna Reference Point
- AS - Anti-spoofing
- ASI – Italian Space Agency
- Atmospheric Delay
- Atmospheric Loading
- Atomic Clock
B
- B1 / B2 / B3 - BeiDou frequencies
- Baseline
- Bathymetry
- BCRS – Barycentric Celestial Reference System
- BDS - BeiDou Navigation Satellite System
- BeiDou
- Bernese GNSS Software
- BEV - Federal Office of Metrology and Surveying (Austria)
- BGI - International Gravimetric Bureau
- Bias (code/phase bias)
- BIPM – Bureau International des Poids et Mesures
- BKG - Bundesamt für Kartographie und Geodäsie
- BOC - Binary Offset Carrier
- Bouguer Anomaly
- BPSK - Binary Phase Shift Keying
- BRD - Broadcast Ephemeris
- Broadcast Ionospheric Model
- Bruns’ Formula
C
- Cadastre
- Carrier Phase
- Cartesian Coordinate System
- Cartographic projections
- CAS - Commercial Authentication Service
- Caster
- CATREF – Combination and Analysis of Terrestrial Reference Frames
- CDDIS - NASA’s Crustal Dynamics Data Information System
- CDMA - Code Division Multiple Access
- CDP - NASA Crustal Dynamics Project
- CEGRN - Central European GPS Geodynamic Reference Network
- Centrifugal Potential
- Centrifugal Potential (Φ)
- CEO - Celestial Ephemeris Origin
- CEOS – Committee on Earth Observation Satellites
- CEP - Celestial Ephemeris Pole
- CGCN - China Geodetic Coordinate Network
- CHAMP - CHAllenging Minisatellite Payload
- Chandler Wobble
- CHIP (GNSS)
- CIO - Celestial Intermediate Origin
- CIP - Celestial Intermediate Pole
- CIRS - Celestial Intermediate Reference System
- Clock Bias
- CNES – France National Centre for Space Studies
- COB - Communication and Outreach Branch
- CODATA – Committee on Data for Science and Technology
- CODE - Center for Orbit Determination in Europe
- Code C/A
- Code M
- Code P
- Code Y
- Coding (GNSS)
- COMPASS
- Constellation BeiDou
- Constellation GLONASS
- Constellation GNSS
- Constellation GPS
- Control Center (GNSS)
- Convergence time
- Coordinate conversion
- Coordinate System
- COPDESS - Coalition on Publishing Data in the Earth, Space and Environmental Sciences
- Copernicus
- CORS - Continuously Operating Reference Stations
- CORS (GNSS)
- Coseismic deformation
- COSPAR – Commission on Space Research of International Science Council (ISC)
- COST-G - International Combination Service for Time-variable Gravity Fields
- Covariance Function
- Coverage factor
- CPO - Celestial Pole Offsets
- CRF - Celestial Reference Frame
- CRS - Coordinate Reference System
- Crustal loading
- CryoSat
- Cryosphere
- CS - Commercial Service (– Galileo)
- CTOH - Centre de Topographie des Océans et de l'Hydrosphère
- Cut-off Angle
- Cycle Slip
D
- Datum
- Datum Transformation
- DCB - Differential Code Bias
- Decimation (GNSS)
- Deflection of the Vertical
- Degradation (GPS)
- Degree and Order
- DEM - Digital Elevation Models
- DGFI - Deutsches Geodätisches Forschungsinstitut (DGFI-TUM)
- DGNSS - Differential GNSS
- DGPS - Differential GPS
- Differential navigation
- Digital Twin Earth
- Disturbing Potential
- DLR - German Aerospace Center
- DOI - Digital Object Identifier
- DOMES - Directory of Observing Stations (DOMES Number)
- DOP - Dilution of Precision
- Doppler Effect
- DORIS - Doppler Orbitography and Radiopositioning Integrated by Satellite
- DOT - Dynamic Ocean Topography
- Double Difference
- DPOD - DORIS extension to the current ITRF for Precise Orbit Determination
- DSM - Digital Surface Models
- DTM - Digital Terrain Models
- DTRF/DTRF2020
- Dual-frequency
- dUT1
- DVLBI - Differential VLBI
- Dynamic Height
- Dynamic positioning
E
- E1 / E5 / E6 (Galileo Frequencies)
- Earth flattening
- Earth Observation
- Earth Rotation
- Earth System
- Earth system components
- Easting (E)
- ECEF - Earth-Centered Earth-Fixed coordinate system
- ECEF - Earth-Centered, Earth-Fixed Coordinates
- Ecliptic
- ECMWF – European Centre for Medium-Range Weather Forecasts
- EGNOS - European Geostationary Navigation Overlay Service
- EGU – European Geoscience Union (EGU)
- EGVs – Essential Geodetic Variables
- Electron Density
- Ellipsoid (Reference Ellipsoid)
- Ellipsoidal Height
- EOAM - Effective Oceanic Angular Momentum
- EOP - Earth Orientation Parameter
- EPN - European Permanent Network of EUREF
- Epoch (GNSS)
- EPOS – European Plate Observing System
- Equipotential Surface
- ERA - Earth Rotation Angle
- ESA - European Space Agency
- ESTB - EGNOS System Test Bed
- Etalon – Satellite Mission
- ETRS89 - European Terrestrial Reference System 1989
- EUREF - Reference Frame Sub Commission for Europe
- EVGA - European VLBI Group for Geodesy and Astrometry
- EVRF - European Vertical Reference Frame
- EVRS - European Vertical Reference System
- EWS - Emergency Warning Service (Galileo)
F
- FAGS - Federation of Astronomical and Geophysical Data Analysis Services
- FCN - Free Core Nutation
- FDMA - Frequency Division Multiple Access
- FES2014b - Finite Element Solution 2014b
- FICN - Free Inner Core Nutation
- FIG – International Federation of Surveyors
- FKP - Area Correction Parameters
- Flattening (f)
- FOC - Full Operational Capability (GNSS)
- Free-Air Gravity Anomaly
- Fundamental Station
G
- GA – Geoscience Australia
- GAGAN - GPS Aided GEO Augmented Navigation System, India
- GALILEO
- GAMIT - GNSS At MIT
- GAMIT – GNSS Analysis MIT
- GAR19 - Global Assessment Report for 2019
- GAST - Greenwich Apparent Sidereal Time
- GATEW - GNSS Augmentation of Tsunami Early Warning
- GBAS – Ground Based Augmentation System
- GCOS – Global Climate Observing System
- GCRS – Geocentric Celestial Reference System
- GDA2020 - Geocentric Datum of Australia 2020
- GDOP - Geometric Dilution of Precision
- GEMSTONE - GEodetic Measurements by the collocation of Space Techniques ON Earth
- GENESIS - ESA Satellite Mission
- GEO – Group on Earth Observations
- Geocenter
- Geocenter Motion
- Geocentric datum
- Geodesy
- GeodesyML
- Geodetic CRS
- Geodetic Datum
- Geodetic Network
- Geodetic Observatory
- Geographic Coordinates
- Geoid
- Geoid Undulations
- Geometric Geodesy
- Geometric Height
- Geometric levelling
- Geopotential
- Geopotential Coefficients
- Geopotential Number
- Geopotential Number (C)
- GEOS - Geodetic and Earth Orbiting Satellite
- GEOSAT - GEOdesy SATellite
- Geosphere
- GEOSS – Global Earth Observation System of Systems
- GET - Géosciences Environment Toulouse
- GFZ - German Research Centre for Geosciences
- GGIM – United Nations Global Geospatial Information Management
- GGM - Global Gravity Model
- GGOS - Global Geodetic Observing System
- GGOS Core Sites
- GGOS Portal
- GGP - Global Geodynamic Project
- GGRF - Global Geodetic Reference Frame
- GGSC - Global Geodesy Supply Chain
- GIA - Glacial Isostatic Adjustment
- GIM - Global Ionosphere Maps
- Ginan - GNSS Analysis Centre Software
- GipsyX - GNSS Software
- GIS - Geographic Information Systems
- Global Water Cycle
- GLONASS - Global'naya Navigatsionnaya Sputnikovaya Sistema
- GLOSS - Global Sea Level Observing System
- GMSL - Global Mean Sea Level
- GMST - Greenwich Mean Sidereal Time
- GMT - Generic Mapping Tool
- GNSS - Global Navigation Satellite Systems
- GNSS Frequencies
- GNSS-A
- GNSS-R - Reflectometry
- GNSS-RO - GNSS Radio Occultation
- GNSS-Spoofing
- GNSS/Levelling
- GOCE
- GOOS – Global Ocean Observing System
- GPS - Global Positioning System
- GPT - Global Pressure and Temperature model
- GRACE - Gravity Recovery And Climate Experiment
- GRACE Follow-On
- GRACE-FO - Gravity Recovery And Climate Experiment Follow-On
- Gradiometry
- Gravimeter
- Gravimetry
- Gravitational Acceleration
- Gravitational Potential
- Gravitational Potential (V)
- Gravity
- Gravity Anomaly
- Gravity Disturbance
- Gravity Field
- Gravity Gradient
- Gravity Measurement
- Gravity Potential
- Gravity Vector
- GRC - Geophysical Risk and Sustainability
- Greenwich meridian
- Groundwater
- GRS - Geodetic Reference System
- GSC - Geological Survey of Canada
- GSI – Geospatial Information Authority of Japan
- GTEWS - GNSS enhancement for Tsunami Early Warning Systems
- GTRF - Galileo terrestrial reference frame
- GUM - Guide to the Expression of Uncertainty in Measurement
H
- HAM - Hydrological Angular Momentum
- HAS - High Accuracy Service
- HDOP - Horizontal Dilution of Precision
- Height Anomaly
- Height Definition
- Height system (physical vs geometric)
- Helmert Transformation (7-Parameter Transformation)
- Hydrological Loading
- Hydrosphere
I
- IAAC - Ionosphere Associate Analysis Centers
- IACS - International Union of Geodesy and Geophysics
- IAG - International Association of Geodesy
- IAG Commissions
- IAG Services
- IAGA - International Association of Geomagnetism and Aeronomy
- IAGBN - International Absolute Gravity Basestation Network
- IAHS - International Association of Hydrological Sciences
- IAMAS - International Association of Meteorology and Atmospheric Sciences
- IAPSO - International Association for the Physical Sciences of the Oceans
- IAU - International Astronomical Union
- IAVCEI - International Association of Volcanology and Chemistry of the Earth's Interior
- ICC - Inter Commission Committee's of IAG
- ICCC - IAG ICC on Climate Research for Geodesy
- ICCM - IAG ICC on Marine Geodesy
- ICCT - IAG ICC on Theory
- ICESat - Ice, Cloud and land Elevation Satellite
- ICET - International Center for Earth Tides
- ICET - International Center for Earth Tides, ROB, Brussels, Belgium
- ICG – International Committee on Global Navigation Satellite Systems of UNOOSA
- ICGEM - International Centre for Global Earth Models
- ICRF - International Celestial Reference Frame
- ICRF3
- ICRS - International Celestial Reference System
- IDEMS - International Digital Elevation Model Service
- IDS - International DORIS Service
- IERS - International Earth Rotation and Reference Systems Service
- IGETS - International Geodynamics and Earth Tide Service
- IGFS - International Gravity Field Service
- IGiK - Institute of Geodesy and Cartography, Poland
- IGN France - National Institute of Geographic and Forest Information
- IGN Spain - National Geographical Institute of Spain (Instituto Geográfico Nacional de Espania)
- IGRF - International Gravity Reference Frame
- IGRS - International Gravity Reference System
- IGS - International GNSS Service
- IGS-RTS
- IGSN71 - International Gravity Standardization Net 1971
- IGSO – International Geodetic Student Organisation
- IHRF - International Height Reference Frame
- IHRF CC - Coordination Centre
- IHRS - International Height Reference System
- ILRS - International Laser Ranging Service
- ILS - International Latitude Service
- Initial RTK
- InSAR - Interferometric Synthetic Aperture Radar
- Instrumental Drift
- Integer Ambiguity
- Integrity (GNSS)
- IOC - Intergovernmental Oceanographic Commission
- IONEX - IONospheric map EXchange format
- Ionosphere
- Ionosphere
- IPCC – Intergovernmental Panel on Climate Change
- IPP - Ionospheric Pierce Point
- IRI - International Reference Ionosphere
- IRM - IERS/International Reference Meridian
- IRNSS NavIC - Indian Regional Navigation Satellite System
- IRP
- IRS - Inertial Reference System
- ISC - International Science Council
- ISG - International Service for the Geoid
- ISGN - International Space Geodetic Network
- ISO – International Organization for Standardization and its Technical Committee ISO/TC 211
- Isostatic Gravity Anomaly
- ISPRS – International Society of Photogrammetry and Remote Sensing
- ITGRF - International Terrestrial Gravity Reference Frame
- ITGRS International Terrestrial Gravity Reference System
- ITRF - International Terrestrial Reference Frame
- ITRF2014
- ITRF2020 – International Terrestrial Reference Frame 2020
- ITRFxxxx Realisations
- ITRS – International Terrestrial Reference System
- ITU – International Telecommunication Union
- IUGG - International Union of Geodesy and Geophysics
- IVS - International VLBI Service for Geodesy and Astrometry
J
- JAXA - Japan Aerospace Exploration Agency
- JpGU – Japan Geoscience Union
- JPL - Jet Propulsion Laboratory
- JTRF - JPL Terrestrial Reference Frame
K
L
- L1 / L2 / L5 (GPS Frequencies)
- L2C
- LAGEOS - Laser Geodynamics Satellites
- Lantmäteriet – Swedish Mapping, Cadastral and Land Registration Authority
- LARES - Laser Relativity Satellite
- Least Squares Adjustment
- LEO - Low Earth Orbiter
- Level Surface
- Levelling
- LiDAR - Light Detection and Ranging
- LLR - Lunar Laser Ranging
- Local Tie
- LOD - Length of Day
- Love Numbers
- Lower Neutral Atmosphere
- LSC - Least Squares Collocation
M
- Mapping
- MCS - Master Control Station
- MDT - Mean Dynamic Topography
- Mean Tide (MT) system
- Mean-Tide System
- MEO - Medium Earth Orbit
- MGEX - Multi-GNSS Experiment
- Molodensky Theory
- Monofrequency
- MSAS
- MSL - Mean Sea Level
- MSS - Mean Sea Surface
- Multifrequency
- Multipath
- Multiplexing
N
- NAGU - (Notice Advisory to Galileo Users)
- NANU - Notice Advisory to Navstar Users
- NAREF - North American Reference Frame
- NASA - National Aeronautics and Space Administration
- Navigation
- Navigation
- Navigation Data
- Navigation Message
- NAVSTAR - NAVigation System by Timing And Ranging
- Network Adjustment
- Neutral Atmosphere
- NGS - National Geodetic Survey
- NIMA - National Imagery and Mapping Agency
- NIST – National Institute of Standards and Technology
- NMEA - National Marine Electronics Association
- NNR - No-Net-Rotation
- NNT - No-Net-Translation
- NOAA - National Oceanic and Atmospheric Administration
- NOC - National Oceanography Centre
- Non-Tidal Gravity Variation
- Normal Gravity
- Normal Gravity Field
- Normal Height
- NPPK - Network Post Processing Kinematic
- NRCan – Natural Resources Canada
- NRO - Non-Rotating Origin
- NRT - Near Real Time
- NRTK - Network Real Time Kinematic
- NTRIP - Networked Transport of RTCM via Internet Protocol
- Nutation
O
- Observation Equation
- Ocean Tides
- Oceanic Loading
- OGC – Open Geospatial Consortium
- OMCT – Ocean Model for Circulation and Tides
- Orbitography
- Orthometric Height
- OS - Open Service (Galileo)
- OSGEO – Open Source Geospatial Foundation
- OSNMA - Open Service Navigation Message Authentication
- OSR - Observation Space Representation
- OST - Ocean Surface Topography
- OTF - On The Fly ambiguity resolution
P
- Path Delay
- PCO/PCV – Phase Center Offset / Phase Center Variation
- PDOP - Position Dilution of Precision
- Phase Center
- Photogrammetry
- Physical Geodesy
- Physical Height
- Planetary Geodesy
- Plate Motion Model
- Plate Tectonics
- Plumb Line
- PNT - Positioning, Navigation and Timing
- POD - Precise Orbit Determination
- Polar Motion
- Positioning
- Post-glacial rebound
- PPP - Precise Point Positioning
- Precession
- Precise Ephemeris
- Prime Meridian
- Pseudo-kinematic positioning
- Pseudorange
- PSMSL - Permanent Service for Mean Sea Level
Q
R
- Radio Source
- Rapid static positioning
- Reference Ellipsoid
- Reference Frame
- Reference Potential (W₀)
- Reference System
- Relative positioning
- REM - Reference Earth Model
- RINEX - Receiver INdependent EXchange format
- RLG - Ring Laser Gyroscope
- ROB - Royal Observatory of Belgium
- RT - Real Time
- RTK - Real‑Time Kinematic
- RTPPP - Real-Time Precise Point Positioning
S
- S/X
- SARAO - South African Radio Astronomy Observatory
- Satellite Ephemeris
- Satellite geodesy
- Satellite Gravimetry
- SBAS - Satellite‑Based Augmentation System
- Scale of the Reference Frame
- SCAR - Scientific Committee on Antarctic Research
- SCoG – Subcommittee on Geodesy (UN-GGIM)
- Sentinel
- SG - Superconducting Gravimeters
- SHAO - Shanghai Astronomical Observatory, China
- SINEX - Solution INdependent EXchange format
- SIRGAS - Geocentric Reference System for the Americas
- SLA - Sea Level Anomalies
- SLR - Satellite Laser Ranging
- SMAP - Soil Moisture Active Passive (SMAP) Microwave Radiometer Mission
- SMOS - Soil Moisture and Ocean Salinity
- Solid Earth Tides
- SONEL - Système d’Observation du Niveau des Eaux Littorales
- SouthPAN - Southern Positioning Augmentation Network
- Space geodesy
- Space Weather
- Spherical Harmonics
- Splicing (GNSS)
- SSH - Sea Surface Height
- SSR - State Space Representation
- SSTop - Sea Surface Topography
- Statens Kartverk – Norwegian Mapping Authority
- Static positioning
- STEC - Slant Total Electron Content
- Stochastic Model
- Stokes’ Formula
- Stop-and-go positioning
- Strainmeters
- Stratosphere
- Subduction
- swisstopo – Federal Office of Topography (Switzerland)
T
- TAI-International Atomic Time
- TCG – Terrestrial Coordinated Time (Fr. Temps-Coordonnee Geocentrique)
- TEC - Total Electron Content
- Tectonic Plates
- Telluroid
- TGP - Tide-Generating Potential
- Thermosphere
- Tidal Gravity Variation
- Tidal Loading
- Tide Free (TF) system
- Tide Gauge
- Tide-Free System
- Tides
- TIGA - Tide Gauge Benchmark Monitoring
- Tiltmeters
- Time Scales
- TIO - Terrestrial Intermediate Origin
- TIRS - Terrestrial Intermediate Reference System
- TLRS - Transportable Laser Ranging System
- TOPEX - Ocean TOPography EXperiment
- Topographic mapping
- TRF - Terrestrial Reference Frame
- Triangulation
- Trilateration
- Troposphere
- TRS - Terrestrial Reference System
- TT – Terrestrial Time
- TUJJB - Turkish Union of Geodesy and Geophysics
- TZD - Tropospheric Zenith Delay
U
- UELN - United European Levelling Network
- UN - United Nations
- UN-GGCE – United Nations Global Geodetic Center of Excellence
- UN-GGIM – United Nations Initiative on Global Geospatial Information Management
- UN-SPIDER – Space-based Information for Disaster Management and Emergency Response of UNOOSA
- UNAVCO
- Uncertainty
- UNDRR – United Nations Office for Disaster Risk Reduction
- UNESCO - United Nations Educational, Scientific and Cultural Organization
- UNOOSA – United Nations Office for Outer Space Affairs
- USNO - United States Naval Observatory
- UT1 - Universal Time 1
- UTC - Coordinated Universal Time
V
- Variance–Covariance Matrix
- Vertical Gradient of Gravity
- VGOS - VLBI Global Observing System
- VieVS - Vienna VLBI Software, TU Wien, Austria
- VLBI - Very Long Baseline Interferometry
- VTEC - Vertical Total Electron Content
- VTRF - VLBI Terrestrial Reference Frame
W
Z
IAG as part of the IUGG
IAG Related Organisations
IAG collaborates closely with numerous organizations within geodesy and beyond. See the list for details.
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