Global positioning system
From Glossary of Meteorology
Global Positioning System
(Abbreviated GPS.) A navigation system based on a constellation of 24 low earth-orbiting satellites having highly accurate clocks and the computational capacity to triangulate positions near the earth's surface.
Developed by the U.S. Department of Defense, the system has the capability of determining position to an accuracy of 30–100 m. If systems at two locations are used with long integration times, positions may be determined within millimeters of a known reference position.