The International Terrestrial Reference System (ITRS) describes procedures for creating

reference frame In physics and astronomy, a frame of reference (or reference frame) is an abstract coordinate system, whose origin, orientation, and scale have been specified in physical space. It is based on a set of reference points, defined as geometric ...

s suitable for use with measurements on or near the Earth's surface. This is done in much the same way that a physical standard might be described as a set of procedures for creating a ''realization'' of that standard. The ITRS defines a

geocentric In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, an ...

system of coordinates using the SI system of measurement. An International Terrestrial Reference Frame (ITRF) is a realization of the ITRS. Its origin is at the center of mass of the whole earth including the oceans and atmosphere. New ITRF solutions are produced every few years, using the latest mathematical and surveying techniques to attempt to realize the ITRS as precisely as possible. Due to experimental error, any given ITRF will differ very slightly from any other realization of the ITRF. The difference between the latest as of 2006

WGS 84 The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also descri ...

(frame realisation G1150) and the latest ITRF2000 is only a few centimeters and RMS difference of one centimeter per component. The ITRS and ITRF solutions are maintained by the

International Earth Rotation and Reference Systems Service The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation P ...

(

IERS The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation P ...

). Practical navigation systems are in general referenced to a specific ITRF solution, or to their own coordinate systems which are then referenced to an ITRF solution. For example, the ''Galileo Terrestrial Reference Frame'' (''GTRF'') is used for the

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

navigation system; currently defined as ITRF2005 by the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

Versions

The ITRF realizations developed from the ITRS since 1991 include the following versions:

Users

GNSS systems: *

Terrestrial Reference Frame (GTRF), ITRF2005; own implementation using IGS sites. * GPS just uses

, ITRF2020 since January 2024 (but used many versions of WGS 84 before), a little modified with International GNSS Service (IGS) implementation, IGS20. *

BeiDou The BeiDou Navigation Satellite System (BDS; ) is a satellite-based radio navigation system owned and operated by the China National Space Administration. It provides geolocation and time information to a BDS receiver anywhere on or near the ...

Coordinate System, China Terrestrial Reference Frame (CTRF) 2000 = ITRF97 at epoch 2000.0; own implementation. *

GLONASS GLONASS (, ; ) is a Russian satellite navigation system operating as part of a radionavigation-satellite service. It provides an alternative to Global Positioning System (GPS) and is the second navigational system in operation with global cove ...

PZ-90.11 is nominally its own system, but is quite close to ITRF and uses many of the same techniques. National systems: * United States: WGS 84 (see above); domestic use is mainly based on

NAD 83 The North American Datum (NAD) is the horizontal datum now used to define the geodetic network in North America. A datum is a formal description of the shape of the Earth along with an "anchor" point for the coordinate system. In surveying, c ...

instead. * China: CTRF 2000 per above. The GPS reference epoch was moved from 2000.0 to 2001.0 in G1150 due to the magnitude 7.9 Denali Fault earthquake in Alaska in November 2002. Still in 2022 ITRF2020 was released, yet GPS was only using G2139 in its antennas, which was aligned to ITRF2014 (IGb14) (though at epoch 2016.0, not reference epoch 2010.0). On 7 January 2024 move to IGS20 happened, so WGS 84 is now aligned with ITRF2020, including PSD (post-seismic deformation), also called G2296. On the other hand GLONASS is using PZ-90.11, which is close to ITRF2008 at epoch 2011.0 and is using 2010.0 epoch (that means when you use reference transformation to PZ-90.11 you will get January 2010 date).

References

{{Reflist

External links

Forward and backward transformations using 14 parameters Helmert

Convertor between ITRF realisations with changing the epoch and tectonics
for it
What is ITRF?

Terrestrial reference systems and frames
(PDF; chapter 4 of IERS Conventions 2010) Geodetic datums

Versions

Users

See also

References

External links