A
geographic coordinate system enables every location on the earth to be specified, using mainly a
spherical coordinate system. There are three coordinates latitude, longitude and geodesic height.
The earth is not a sphere, but an irregular changing shape approximating to an ellipsoid; the challenge is to define a coordinate system that can accurately state each topographical feature as an unambiguous set of numbers. [1]
The line passing through the (former) Royal Observatory, Greenwich (near London in the UK) has been chosen as the international zero-longitude reference line, the Prime Meridian. Places to east are in the eastern hemisphere, and places to the west in the western hemisphere. The antipodal meridian of Greenwich is both 180°W and 180°E. The choice of Greenwich is arbitrary, and in other cultures and times in history other locations have been used as the prime meridian.[2]
Thus there are several formats for writing degrees, all of them appearing in the same Lat,Long order.
