How Does GPS Actually Find You?

Imagine you are in a giant park. You close your eyes and shout. If you hear the echo come from the north in two seconds, and the east in three seconds, you can guess where you stand. GPS works exactly like this but with satellites instead of echoes.

There are many satellites flying high above Earth. They carry special atomic clocks that tick incredibly fast. These satellites send out radio signals that travel at the speed of light.

Your phone catches these signals. It measures how long each signal took to arrive. If a signal takes one second, it is far away. If it takes two seconds, it is farther still. By looking at several satellites, your phone draws circles around itself. Where the circles overlap is where you are.

You might wonder why we need four signals instead of three. The first three tell us where you are on a map. The fourth satellite helps correct for time. Even a tiny error in the clock can put you miles off track. So, your phone uses that extra signal to get the perfect spot.