How a Tiny Watch Finds You ANYWHERE With GPS

A watch on your wrist can pinpoint you anywhere on Earth, just by listening for clocks in space.

How can a tiny watch know exactly where you are, using satellites thousands of miles away?

Every GPS satellite carries an atomic clock and broadcasts who it is and the exact time it sent the signal. Your watch compares when the message arrived to when it was sent. That gap, times the speed of light, gives the distance to that satellite. One distance puts you on a giant sphere around it. A second satellite, and you sit where two spheres overlap. A third narrows it further. This is trilateration, stacking distances until only one point on Earth fits them all.

There is a catch: your watch has no atomic clock, so its own timing is slightly off. That is why it needs a fourth satellite. The extra distance lets it solve for the clock error too, correcting itself from space.

Follow The Explainer Vault — because everything has an explanation.