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IERS Reference Meridian
International prime meridian used for GPS and other systems / From Wikipedia, the free encyclopedia
This article is about Earth's current international standard prime meridian. For the historical prime meridian, see Prime meridian (Greenwich).
For the general concept, see prime meridian.
The IERS Reference Meridian (IRM), also called the International Reference Meridian, is the prime meridian (0° longitude) maintained by the International Earth Rotation and Reference Systems Service (IERS). It passes about 5.3 arcseconds east of George Biddell Airy's 1851 transit circle which is 102 metres (335 ft) at the latitude of the Royal Observatory, Greenwich.[1][2][lower-alpha 1] Thus it differs slightly from the historical Greenwich Meridian.
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It is the reference meridian of the Global Positioning System (GPS) operated by the United States Space Force, and of WGS 84 and its two formal versions, the ideal International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).