ELI5: how gps works

// eli5

What is GPS?

GPS is like a treasure hunt game where satellites in space help your phone figure out exactly where you are on Earth [1]. There are more than 30 satellites floating around above us, and they're constantly sending out radio signals that say "Hi, I'm here!" [1][5].

How does it find you?

Your phone listens to signals from at least four satellites at the same time [4]. Each satellite tells your phone how far away it is, kind of like if your friends shouted from different parts of a playground and you timed how long it took to hear them [4]. By hearing from four satellites, your phone can figure out exactly where you are.

Why does it need four satellites?

Three satellites can tell you roughly where you are, but the fourth one helps make sure the answer is really accurate [4]. It's like asking three friends where they think you are—one answer might be close, but asking a fourth friend confirms it.

How do you use it?

Your phone has a GPS receiver inside that picks up these satellite signals automatically [1]. Once it knows where you are, it can show you a map, give you directions, or tell you what restaurants are nearby.