GPS - Global positioning system. A system of satellites and receiving devices used to compute positions on the Earth. GPS is used in navigation, and its precision supports cadastral surveying. Latitude and longitude are angles measured from the Earth's center to locations on the Earth's surface. Latitude measures angles in a north-south direction.
Longitude measures angles in the east-west direction.
Conceptually, layers in a database or map library environment are exactly like coverages. See also ArcStorm database and map library. The reference area on a map that lists and explains the colors, symbols, line patterns, shadings, and annotation used on the map. The legend often includes the scale, origin, orientation, and other map information. The symbol key used to interpret a map.