Written by Tadashi Moody
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The global positioning system (GPS for short) is a network of satellites, signals, ground-based hardware and software, and people which makes it possible to identify precise positions on the Earth's surface. It was originally created by the United States Department of Defense, and intended for military applications. However, in 1980 use of this system was made available to the general public, opening a whole new industry and a world of possible applications.

At its core, GPS is a network of twenty-four satellites circling the globe in a precise orbit, and continually transmitting time-coded signals to the Earth's surface. A GPS receiver on the ground, such as a handheld unit made by Garmin, can use the signals from three or more satellites to calculate its precise location in the three dimensions X, Y, and Z. These dimensions can be converted into a georeferencing system such as latitude, longitude and elevation.

How Does GPS Work?

A GPS receiver is able to calculate how long a signal took to reach it from a particular satellite, which can be translated into distance. Once the receiver has calculated its distance to three or more satellites, it can locate itself on the globe. With four or more satellite distances calculated, a GPS receiver can also calculate elevation.

Because these calculations are continuous, a GPS receiver can track its own movement. This allows it to calculate such information as speed, bearing and distance to a given destination. This capability has made GPS receivers a truly revolutionary tool for navigation, as they are now commonly used by aviators, mariners, recreationists, automobile owners, and many, many others.

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