Meridian

A meridian is a line of longitude extending from the North Pole to the South Pole. Meridians locate places by measuring angular distance east or west of a reference meridian.

Longitude: Longitude is the angular distance east or west of a reference meridian, usually measured in degrees. A meridian is one line in the coordinate system that longitude measures.
Great circle: A great circle is a circle on a sphere whose plane passes through the sphere’s center. Each meridian forms half of a great circle completed by its opposite meridian.
Greenwich meridian: The Greenwich meridian is the zero-degree meridian passing through the Royal Observatory in Greenwich, London. It is the internationally adopted prime meridian.
Geodesic: A geodesic is the shortest path between points on a curved surface, locally following a straightest possible route. Meridians are geodesics on an ideal spherical Earth.
Latitude: Latitude is the angular distance north or south of the equator, measured in degrees. Latitude and meridians together specify geographic coordinates.
Prime meridian: The prime meridian is the designated zero-degree line of longitude from which east and west are measured. It supplies the reference needed to assign longitude to every other meridian.
International Meridian Conference: The International Meridian Conference was an 1884 meeting in Washington, D.C., that considered a universal prime meridian. Its delegates selected Greenwich as the standard reference meridian.
Global Positioning System: The Global Positioning System is a satellite-based navigation system that provides position and time information worldwide. GPS positions are commonly expressed as latitude and longitude relative to geodetic meridians.
Geographic coordinate system: A geographic coordinate system identifies locations on Earth using coordinates such as latitude and longitude. Meridians provide the north–south reference lines used by this system.
Antimeridian: The antimeridian is the meridian opposite a chosen meridian, 180 degrees away around Earth. It pairs with a meridian to complete a great circle.

Linked from 10 pages