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GPS
= Global Positioning System
The Global Positioning System is a constellation of
satellites that orbit the earth twice a day, transmitting
precise time and position (latitude, longitude and altitude)
information. With a GPS receiver, users can determine their
location anywhere on the Earth. Position and navigation
information is vital to a broad range of professional and
personal activities, including hiking, hunting, camping,
boating, surveying, aviation, national defense, vehicle
tracking, navigation and more.
The complete system consists of 24 satellites orbiting about
12,000 miles above the Earth, and five ground stations to
monitor and manage the satellite constellation. These
satellites provide 24-hour-a-day coverage for both two-and
three- dimensional positioning anywhere on Earth.
Development of the $10 billion GPS satellite navigation
system was begun in the 1970s by the US Department of
Defense, which continues to manage the system, to provide
continuos, worldwide positioning and navigation data to US
military forces around the globe. However, GPS has an even
broader civilian, commercial application. To meet these
needs, GPS offers two levels of service, one for civilian
access and the second encrypted for exclusive military use.
The GPS signals are available to an unlimited number of
users simultaneously, and there is no charge for using the
GPS Satellites either.
 
see also:
How
Does GPS Work?
Who
Uses GPS?
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