What is the definition of prime meridian?

The Greenwich Observatory in London was not accepted as the prime meridian for all countries until the late 19th century, and Withers describes the situation before then--when every country designated its own starting point for navigation and cartography--and afterwards as everyone gradually began using the same zero. read more

Prime meridian definition is - the meridian of 0 degrees longitude which runs through the original site of the Royal Observatory at Greenwich, England, and from which other longitudes are reckoned. read more

prime meridian [prīm] The meridian with a longitude of 0°, adopted officially in 1884 as a reference line from which longitude east and west are measured and as a basis for standardized time zones. read more