What help to locate places on a map?
A grid or a mesh system has been created by man to understand & locate exact location on the earth.This concept was originated long long ago by geographic /geodesic team and the navigators.
George Biddell Airy marked the prime meridian line as zero degree longitude at royal observatory,Greenwich.
similarly The Equator was discovered and mapped out by a French geodesic expedition team lead by Charles-Marie de LaComdamine .