GPS is an acronym for "Global Positioning
System." The 1st GPS satellite was put into space in 1978. GPS
satellites send signals to GPS receivers on the ground. There are at least
24 satellites working at any one time. When the signals from at least three GPS
satellites have been received, the receiver is able to pinpoint location very
precisely. This is expressed in longitude and latitude coordinates, such
as 45 degrees North and 100 degrees West.