Latitude and Longitude, system of geometrical coordinates used in designating
the location of places on the surface of the earth. Latitude, which gives the
location of a place north or south of the equator, is expressed by angular
measurements ranging from 0° at the equator to 90° at the poles. Longitude, the
location of a place east or west of a north-south line called the prime
meridian, is measured in angles ranging from 0° at the prime meridian to 180°
at the International Date Line.
Degrees of latitude are equally spaced, but the slight flattening at the poles
causes the length of a degree of latitude to vary from 110.57 km (68.70 mi) at
the equator to 111.70 km (69.41 mi) at the poles. At the equator, meridians of
longitude 1 degree apart are separated by a distance of 111.32 km (69.17 mi);
at the poles, meridians converge. Each degree of latitude and longitude is
divided into 60 minutes, and each minute divided into 60 seconds, thereby
allowing the assignment of a precise numerical location to any place on earth.