Global Positioning System

GPS is a >Satellite Navigation system used to determine ground position and velocity (location, speed, and direction).

It is made possible by a "constellation" of 24 satellites that orbit the Earth, continually transmitting their changing position with time. The spatial distributon of the satellites allow ground receivers to continually be in contact with 4 satellites, allowing the receivers to collect this data and triangulate their own position to pinpoint their geographic location.

The location accuracy is anywhere from 100 to 10 meters for most equipment and can be improved by using the >Wide Area Augmentation System (WAAS) or Differential GPS (DGPS).

The GPS is owned and operated by the U.S. Department of Defense but is available for general use around the world.