how to understand longitude and latitude
Using the Latitude Longitude Coordinate System. The latitude longitude coordinate system uses angular measurements to describe a position on the surface of the earth. The system has been in use, with little change, since the astronomer Ptolemy used them in his first world atlas in A.D. 150. Mariners and aviators have been the primary users of latitude/longitude in the past. The system is used on a world wide basis and many different types of maps have lat/lon markings.