How many countries does the IERS Reference Meridian (IRM) pass through?

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 m (335 ft) at the latitude of the Royal Observatory, Greenwich. Thus, it differs slightly from the historical Greenwich Meridian (the former world standard).

It has been the international standard for the Earth's prime meridian since 1984, attributed to such new techniques as lunar laser ranging, satellite laser ranging, and very-long-baseline interferometry. IRM has been adopted by the International Hydrographic Organization for all nautical charts since 1983 and by the International Civil Aviation Organization for air navigation since 1989. It is the reference meridian of the Global Positioning System (GPS) and of WGS 84 and its two formal versions - the ideal Int'l Terrestrial Reference System (ITRS) & the realization, the Int'l Terrestrial Reference Frame (ITRF).

On Earth, starting at the North Pole and heading south to the South Pole, the IERS Reference Meridian passes through eight countries (United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Togo and Ghana) and three oceans (Arctic Ocean, Atlantic Ocean and Southern Ocean).