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GPS Explained

GPS (Global Positioning System) is a network of satellites that orbit the earth at fixed points and beam signals to anyone with a GPS receiver. These signals carry a time code and geographical data point that allows the user to pinpoint their exact position, speed and time anywhere on the planet.

Operated by the American Department of Defense, GPS relies on between 24 and 32 satellites that sit in a "constellation" orbiting the planet at a medium earth orbit of at least 20,000 km, which is less than the 35,000 km, that TV, communications and internet satellites, and weather satellites orbit at.

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The more satellites in the global positioning system the better the accuracy of the data received. If one satellite fails or sends out faulty signals, these are cancelled out by readings from another satellite in the constellation.

The global positioning system was designed during the 1960’s with military and intelligence applications in mind at the height of the Cold War. But in 1983, when a Korean passenger plane strayed into Soviet territory and was shot down by the USSR, the US President Ronald Reagan ordered that a civilian version of GPS be made available to everyone. Currently, accessing the GPS using a GPS receiver is free and doesn’t require subscription or maintenance fees.

GPS has come a long way since the 80’s and today GPS is used for dozens of applications including aircraft and shipping navigation, route finding for drivers, map-making, earthquake research, climate studies, animal tracking, farming and outdoor treasure-hunting games known as geocaching.

A typical GPS receiver has an antenna tuned to the frequencies transmitted by the satellites. This picks up the signal and feeds it to the receiver-processor, which then displays location and time very accurately.