GPS coordinates are a unique identifier of a precise geographic location on the earth, usually expressed in alphanumeric characters.
Coordinates, in this context, are points of intersection in a grid system. GPS (global positioning system) coordinates are usually expressed as the combination of latitude and longitude. Latitude is a measure of degrees of distance from the equator, which is 0 degrees. The north and south poles are at 90 degrees in either direction. The prime meridian is 0 degrees longitude and the locations are measured according to 90 degrees east or west from that point.
GPS coordinates are expressed in two different formats. Below are the coordinates for the Empire State Building in New York City:
N40° 44.9064', W073° 59.0735'
That same information can be expressed in a purely numeric format:
In the latter case, the minus sign before the second number indicates that the location is west of the prime meridian; a minus sign in front of the first number would indicate degrees south of the equator.
See a brief tutorial introduction to GPS: