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The group of global reference systems that has the greatest significance and lowest uncertainty is the ITRF, International Terrestrial Reference Frame.
International Terrestrial Reference Frame
The different solutions are designated by the year of the latest data included in the solution, using the format ITRFyy or ITRFyyyy, for example ITRF97 or ITRF2014. New ITRF solutions (new window) are being developed as more data becomes available.
ITRF solutions are based on several different space-based technologies; GNSS, SLR (Satellite Laser Ranging), VLBI (Very Long Baseline Interferometry) and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite). The calculation of ITRF solutions is done as an international collaboration under the IERS, International Earth Rotation Service (new window) and is presented as a set of points with three-dimensional coordinates and velocities.
International Terrestrial Reference System
ITRF are implementations of ITRS, International Terrestrial Reference System (new window). ITRS is the theoretical definition of the reference system, i.e. a number of regulations and conventions that, together with modeling, are required to define the system's origin, scale, orientation and development over time.
Adaptations of ITRF
To adapt the ITRF to a certain type of applications, also other variants of ITRF are made, including the one by IGS, the International GNSS Service (new window). IGS makes adjustments that comply with the antenna models used in the IGS network (new window), which is a global network of permanent GNSS stations. These implementations are called IGSyy, where yy is the same year as the corresponding ITRFyyyy.
Reference frames that are connected to ITRF
Most modern three-dimensional reference systems are today connected to one of the ITRF solutions. This also applies to the reference systems for the various satellite navigation systems, e.g. WGS 84 used by the GPS system, PZ‑90.11 for the Russian Glonass, GTRF which is the reference system for European Galileo and the Chinese CGCS 2000 which is the reference system for Beidou.
More information
Here you will find additional information related to ITRS and ITRF:
- ITRF2014, A new release of the International Terrestrial Reference Frame modeling nonlinear station motions (new window)
- ISO standard 19161‑1 (new window) Geographic information – Geodetic references – Part 1: International terrestrial reference system (ITRS)
- Transformation between ITRF and SWEREF 99