The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.

GPS uses these satellites as reference points to calculate extremely accurate positions, in some cases as accurate as one centimeter.

GPS works using the concept of "triangulation". To triangulate, a GPS receiver measures distance using the travel time of radio signals between the GPS receiver and a GPS satellite.

For a more in-depth description of how a GPS works and a demonstration, click here