Latitude is the angular distance on Earth measured north or south of the equator, at 0 degrees latitude, in degrees, minutes, and seconds. The equator is the longest latitude line on Earth, measuring 24,901.55 miles. This location stands at the North 45th parallel of latitude, halfway between the equator and the North Pole. Longitude is the angular distance on Earth measured east or west of the meridian at Greenwich, England, at 0 degrees longitude, in degrees, minutes, and seconds. Longitude lines run from the North Pole to the South Pole. This location stands at the West 90th meridian of longitude, a quarter of the way around the world from Greenwich, England. The latitude and longitude coordinate system uses angular measurements to describe a position on the surface of the earth. It is used worldwide, though mariners and aviators have been its primary users. The system has been in use with little change since the astronomer Ptolemy used it in his first world map in 150 CE.