IERS Reference Meridian

Line across the Earth
Modern IERS Reference Meridian on Earth
Countries that touch the Equator (red) and the Prime Meridian (blue)

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][a] Thus it differs slightly from the historical Greenwich Meridian.

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).

  1. ^ Cite error: The named reference Malys2015 was invoked but never defined (see the help page).
  2. ^ IRM on grounds of Royal Observatory from Google Earth Accessed 30 March 2012


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