Meridian A meridian is a line of longitude terminated by the North Pole and the South Pole. It is half of an imaginary great circle on the Earth's surface. The position of a point along the meridian is given by its longitude and latitude, and measured in angular degrees north or south of the Equator. A meridian is measured in angular degrees east or west of the prime meridian in Greenwich, England. For instance, the line of longitude passing through the prime meridian is internationally accepted as the line of 0° of longitude.
