How Does a GPS Receiver Work?
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Introduction
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In 1973, the Department of Defense developed the Global Positioning System as a military tool that could help vehicles and soldiers determine their location at any time. Today, laypeople use GPS technology all the time. Not only that, but scientists use GPS technology as well. For example, meteorologists use GPS technology to forecast the weather and study global climate.
The Satellites
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A GPS receiver works because it communicates with satellites orbiting Earth. The job of each satellite is to transmit information about its current location (latitude, longitude and height) to the GPS receivers on Earth. The signals move at the speed of light and are synchronized so that they arrive at the receivers at almost the same instant. The satellites are operated by the U.S. Air Force, and there are 24 satellites in orbit at any given time.
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Trilateration
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An antenna on Earth receives the signals from the satellites and transmits them to the receiver via electric currents. Through a mathematical principle called trilateration, the receiver calculates its own location. It does this by measuring the distance between itself and each satellite. This calculation narrows down the location of the receiver to a certain sphere. Each point on that sphere is the same distance from the satellite. By repeating this process with at least two more satellites, the receiver can calculate where the three spheres overlap. This process will provide the receiver with its location.
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