Global Positioning System

In GPS, it is the distance and direction from the navigator’s receiver to two or more satellites orbiting Earth. GPS consists of three types of components: satellites in space, control devices on land, and receivers on a craft or carried by hand. Twenty-four artificial satellites orbit 12,500 miles (20,117 kilometers) above the Earth’s surface. On land, electronic control devices track the movement of the satellites and send them signals coded with their precise locations. The satellites continuously broadcast signals telling their exact location and the time each signal was sent. A craft’s receiver picks up these signals. When the receiver picks up signals from two satellites, its internal computer calculates the position of the craft and displays it for the navigator to read and use.