How GPS works: how your phone knows where you are
Trilateration: how GPS finds your place, and why a cheap clock breaks it
One GPS satellite can tell your phone how far away it is, and nothing more. That leaves a whole circle of places where you could stand. How many distances does it take to leave just one?
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1
The answer to the cheap clock comes in two steps, and the first one is on a map. Satellite 7 gave your phone one distance. On the map, that is a wide circle, and you are somewhere on it.
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2
At the same moment, your phone hears satellite 12 and gets a second distance, so a second circle. The two circles cross at two spots, far apart. Which one is you?
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