How does a GPS device know where I am?

A GPS device knows where you are by talking to special satellites way up in space.

Imagine you're playing hide and seek with your friends. You can’t see them, but you can hear them shout. The louder they shout, the closer they are. A GPS device works kind of like that, it listens to satellites shouting from far away in the sky.

The GPS device sends out a signal and waits for satellites to reply. Each satellite says, “I’m here!” with a tiny time delay. By listening to at least three satellites, the GPS can figure out how far it is from each one, just like you would guess your friend’s location by how loud their shout sounds.

Once the GPS knows how far it is from three satellites, it uses that information to find your exact spot on Earth. It’s like drawing circles around each satellite, where they overlap is your location! And that's how a GPS device knows exactly where you are, even when you're playing hide and seek in the park.