<P> An absolute location is designated using a specific pairing of latitude and longitude in a Cartesian coordinate grid--for example, a Spherical coordinate system or an ellipsoid - based system such as the World Geodetic System--or similar methods . For instance, the position of Lake Maracaibo in Venezuela can be expressed approximately in the WGS84 coordinate system as the location 9.80 ° N (latitude), 71.56 ° W (longitude). It is, however, just one way . Alternative ways can be seen in this Geo Hack link: 9 ° 48 ′ N 71 ° 34 ′ W ﻿ / ﻿ 9.80 ° N 71.56 ° W ﻿ / 9.80; - 71.56 . </P> <P> Absolute location, however, is a term with little real meaning, since any location must be expressed relative to something else . For example, longitude is the number of degrees east or west of the Prime Meridian, a line arbitrarily chosen to pass through Greenwich, London . Similarly, latitude is the number of degrees north or south of the Equator . Because latitude and longitude are expressed relative to these lines, a position expressed in latitude and longitude is actually a relative location . </P>

When do we use the method of relative location