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FAQ > How does GPS "triangulation" work? (Q0110)

## How does GPS "triangulation" work?

For this exercise, you'll need to dust off some simple skills you learned in geometry. Start by imagining a "distance sphere" (in three dimensions) surrounding a GPS satellite. Points on the surface of the sphere are all the same distance from the satellite that's located exactly at the center.

- knowing distance from one satellite places you somewhere on a spherical surface that's centered around the satellite

- knowing distances from two satellites places you somewhere along a circle that's between the two satellites (defined by the intersection of their "distance spheres")

- distances from three satellites usually intersect at two points, and if you're not flying around, one of these points will be on Earth's surface

- distances from four or more GPS satellites will intersect at just one point

This process works by finding the intersection of your *distances* from three or more satellites. Thus, describing it as "trilateration" is actually better than "triangulation", but neither term seems precisely correct from a technical standpoint.

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