The Prime Meridian is the imaginary line of zero longitude, the geographic starting point for any East-West degree measurement of any place on the Earth.  It was selected by an international delegation that convened in 1884 in Washington, DC.  It’s a North-South imaginary line that run right through the Airy transit circle at the Royal Observatory in Greenwich, England.  This is also where we get the measurement of Greenwich Mean Time (GMT). As our ability to measure position and time improves with the Global Positioning System (GPS), the precise position of the prime meridian has actually changed, moving 102 meters East...