Prime meridian (Greenwich)
THE MERIDIAN OF THE BRITISH ROYAL OBSERVATORY IN GREENWICH, ENGLAND, WHEN DISTINGUISHED FROM THE GENERAL CONCEPT OF A PRIME MERIDIAN
Greenwich Meridian Line; Greenwich Meridian; Greenwich meridian; Prime Meridian (Greenwich); Greenwich Prime Meridian; Nullmeridian; Airy meridian
The historic prime meridian or Greenwich meridian is a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. The modern IERS Reference Meridian widely used today is based on the Greenwich meridian, but differs slightly from it.