he Global Positioning System, more commonly known by its acronym, GPS, is the only completely functioning Global Navigation System (GNSS). As it was developed and continues to be maintained by the US Department of Defense, other countries including Russia, the EU, China and India are all in various stages of creating their own systems.

In the mean time, the American GPS system, as the first and still only fully functional GPS system, is utilized worldwide by individuals, scientists, militaries, and for all manner of commercial and recreational uses.

GPS, which can pinpoint your position anywhere on the Earth, day or night, within 10-20 feet, plus other capabilites, utilizes at least 24 Medium Earth Orbit Satellites maintaining exactly calibrated orbits. The satellites transmit precise microwave signals, which enables your automotive, marine or hand held GPS receiver to determine your exact location, speed, direction, and time.

The constellation of GPS satellites is controlled and maintained by the United States Air Force 50th Space Wing, at a cost of approximately US$800 million per year, which includes replacement of aging satellites as well as ongoing research and development.

Until 1983, the US GPS system was reserved solely for military use. But after the incident where Korean Airlines Flight 007 went off course and was shot down by Soviet fighters, President Ronald Reagan ordered the GPS system to be made freely available to all the world for the common good of mankind, and there are no subscription or other fees to use it. Since then GPS use has become nearly ubiquitous for everything from cell phones, map making, land surveying, auto travel, hiking, and a wide range of commercial and scientific uses.

Every GPS satellite circles the earth twice a day in a very exact orbit and transmits unique signal information to earth. GPS receivers such as the type you might use in your car, boat or on a hike, receive satellite signals from at least three satellites and use this information to triangulate and calculate the GPS units (and your) exact location, by measuring and comparing the time signals transmitted by the satellites to the time they were received by the GPS device. The measurement of time from three or more satellites, pinpoints the GPS devices location, which can then be displayed on a map and continuously updated. With a GPS you can never get lost and all of your activities become a lot more fun!

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