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| International Terrestrial Reference System | |
|---|---|
| Name | International Terrestrial Reference System |
| Established | 1988 |
| Administered by | International Earth Rotation and Reference Systems Service |
| Components | Geocenter definition; scale convention; orientation conventions |
| Primary use | Geodesy; Geophysics; Satellite navigation; Space missions |
International Terrestrial Reference System is the geocentric, kinematic coordinate system used for precise positioning of points on and near the Earth surface, supporting activities ranging from satellite navigation to space missions. It underpins global efforts in geodesy, ties together observations from Very Long Baseline Interferometry, Global Navigation Satellite Systems, Satellite Laser Ranging, and Doppler tracking, and interfaces with time standards and Earth orientation products issued by international agencies.
The system provides a standardized spatial and temporal foundation linking instruments such as Very Long Baseline Interferometry, Global Positioning System, GLONASS, Galileo (satellite navigation), and BeiDou to terrestrial networks used by agencies like the International Earth Rotation and Reference Systems Service, International Association of Geodesy, European Space Agency, National Aeronautics and Space Administration, and Japan Aerospace Exploration Agency. It integrates reference products delivered by analysis centers including the National Geospatial-Intelligence Agency, United States Naval Observatory, Royal Observatory of Belgium, and the German Research Centre for Geosciences (GFZ). The system interacts with time references maintained by the International Bureau of Weights and Measures, International Atomic Time, and the International Celestial Reference Frame through Earth orientation parameters produced by the International Earth Rotation Service and successor bodies.
The formal definition prescribes a geocenter, scale, and orientation consistent with relativistic conventions adopted by the International Astronomical Union and the Bureau International de l'Heure. Realizations of the system, known as International Terrestrial Reference Frames, are computed by combining observations from networks operated by the International GNSS Service, International Laser Ranging Service, International VLBI Service for Geodesy and Astrometry, and the International DORIS Service managed by entities like the Centre National d'Études Spatiales and CNES. Individual frame solutions are generated by analysis groups at institutions such as the Jet Propulsion Laboratory, European Centre for Medium-Range Weather Forecasts, Observatoire de Paris, and the Geodetic Survey of Canada.
Successive reference frames (e.g., ITRF versions) are released at epochs tied to observational spans and include station coordinates, velocities, and reference epoch information used by users including the United States Geological Survey, National Oceanic and Atmospheric Administration, European Space Agency, and national mapping agencies such as the Ordnance Survey (United Kingdom), Institut Géographique National (France), and the Federal Agency for Cartography and Geodesy (Germany). Epoch specification connects to campaigns like the TOPEX/Poseidon and Jason (satellite), as well as to tectonic and geophysical events recorded by observatories such as USGS Hawaiian Volcano Observatory and networks like the Global Seismographic Network.
Coordinate transformations between terrestrial frames and celestial frames require Earth orientation parameters derived from analyses at centers including the International Earth Rotation and Reference Systems Service and the United States Naval Observatory. Transformations incorporate relativistic time scales such as Coordinated Universal Time, International Atomic Time, and conventions from the International Astronomical Union and tie to celestial frames like the Hipparcos catalog and the Gaia (spacecraft) results used by institutions such as the European Southern Observatory and Royal Greenwich Observatory heritage datasets.
Users span space agencies NASA, ESA, Roscosmos, CNSA, and commercial actors in satellite operations, surveying firms, and scientific communities including researchers at Scripps Institution of Oceanography, Lamont–Doherty Earth Observatory, Max Planck Institute for Solar System Research, and CNES. Applications include satellite orbit determination for missions like International Space Station, geodynamic studies by groups at the British Geological Survey, sea level monitoring used by the Intergovernmental Panel on Climate Change reports, and navigation services operated by companies such as Garmin and consortiums like the European GNSS Agency.
Frame accuracy and stability are assessed through intercomparisons by analysis centers including IGN (Spain), Istituto Nazionale di Geofisica e Vulcanologia, Observatoire de la Côte d’Azur, and maintained by the International Earth Rotation and Reference Systems Service through continuous observations from networks like the International GNSS Service and International Laser Ranging Service. Performance metrics reference station coordinate repeatability, geocenter motion studied with contributions from Scripps Institution of Oceanography and GFZ Potsdam, and long-term stability evaluated by groups at University of Bern and the Harvard-Smithsonian Center for Astrophysics.
Development traces through milestones involving the International Astronomical Union, the International Union of Geodesy and Geophysics, and the formation of services such as the International Earth Rotation Service and later the International Earth Rotation and Reference Systems Service. Key technical contributions came from institutions including the Jet Propulsion Laboratory, US Naval Observatory, Observatoire de Paris, National Geospatial-Intelligence Agency, Bureau International de l'Heure, and national agencies like Geoscience Australia and Institut Géographique National (France), while projects such as SEASAT, TOPEX/Poseidon, and GRACE (satellite) drove requirements for improved realizations.
Category:Geodesy Category:Reference systems