THE BASICS
- GPS (global positioning system) is based on satellites orbiting earth, and GPS receivers (what you hold).
- There are 24 GPS satellites orbiting earth, and they are maintained by the U.S. Department of Defense. There are others, such as GLONASS and Galileo, but they are covered in the history section.
- GPS receivers calculate their position using trilateration from satellites. Trilateration is a means of calculating position based on the distance from three or more satellites using the satellites as reference positions. Trilateration is ofter mistakenly called triangulation, which is position based on angles.
- But how do you calculate distance from objects moving around in space?
- Receivers calculate distance by figuring out the time that it takes a radio signal to travel from the satellite to the receiver.
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Distance = Velocity (of signal) x Time (to reach the receiver)
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