Terrestrial Reference Frame
How can we provide a stable reference for measuring changes of our planet?
The Terrestrial Reference Frame is a global standard for accurately defining positions on or near the Earth’s surface over time. It forms the basis of modern national geodetic systems and supports applications such as mapping, geographic information systems, 3D modelling, surveying, navigation, precision agriculture, location-based services, etc. The TRF also serves as the reference frame for Earth system science, facilitating the precise monitoring of long-term and transient processes such as tectonic plate movements, sea-level rise, ice melting, surface deformation, etc. These high-precision observations are vital for comprehending and addressing environmental and societal challenges.
The International Association of Geodesy (IAG) recommends the International Terrestrial Reference Frame (ITRF) as the standard terrestrial reference frame for positioning, satellite navigation and Earth science applications, as well as for the definition and alignment of national and regional geodetic reference frames (see IAG Resolution No. 1, 2019). The importance of geodetic reference frames has been recognized by the United Nations, too. In February 2015, the UN General Assembly adopted its first geospatial resolution “A Global Geodetic Reference Frame for Sustainable Development”.
The ITRF provides the fundamental basis to refer the geodetic observations and estimated parameters to a unified global basis. High accuracy, consistency and long-term stability are required for precisely monitoring global change phenomena as well as for precise positioning applications on and near the Earth’s surface. The ITRF comprises concrete points (markers) attached to the solid Earth crust with precisely determined coordinates (mean 3D positions of the stations and their motions).
IERS – ITRS Centre
Within the International Earth Rotation and Reference Systems Service (IERS), the ITRS Centre (IGN, France) is responsible for the maintenance of the ITRS/ITRF, including network coordination, for providing the ITRS Combination Centers with specifications, and for evaluating their respective results. The ITRS Combination Centers are responsible to provide ITRF products by combining ITRF inputs from the Technique Centers and others. ITRS Combination Centers are currently maintained by IGN (Paris, France), DGFI-TUM (Munich, Germany) and JPL (Pasadena, USA).
The latest realization, the ITRF2020 has been released by the ITRS Center in 2022. The ITRF2020 is based on the input data time series of station positions and Earth Orientation Parameters (EOPs) provided by the Technique Centers (IGS; ILRS; IVS; IDS) of the four space geodetic techniques GNSS, SLR, VLBI and DORIS).
The global ITRF is extended by means of regional densifications, called Regional Terrestrial Reference Frames (RTRF), providing coordinates and time series of additional terrestrial sites or points needed to provide access to the global reference frame anywhere on the Earth’s surface.
Data Sources
- ITRS Centre: The ITRS Centre is responsible for the maintenance of the International Terrestrial Reference System (ITRS) and the International Terrestrial Reference Frame (ITRF). It is maintained by IGN in France.
- ITRS Combination Centers: Institut national de l’information géographique et forestière (IGN), Paris, France
Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Technische Universität München, Munich, Germany
NASA Jet Propulsion Laboratory (JPL), Pasadena, USA - IERS: International Earth Rotation and Reference Systems Service
