As scary as it may be, the US Department of Defense has been using satellite technology to track the location of targets anywhere on Earth with pinpoint accuracy for the last thirty years. GPS, or Global Positioning System technology, lets GPS portable receivers pick up transmissions from four of the twenty-four tracking satellites.
By interpolating the data from the four satellites, GPS portable receivers are able to get a very clear picture of their own longitude and latitude, as well as the correct time. To be able to function properly, however, the GPS portable receiver must be positioned where it the satellite transmissions will not be blocked.
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Gps Portable Devices- The World In The Palm Of Your Hand
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