What Is GPS?
A Global Positioning System (GPS) is a satellite navigation system that works by continually transmitting high-frequency radio signals containing the time and location of the satellite in relation to earth. A GPS receiver on the planet's surface obtains this information from three or more satellites and the GPS receiver calculates the user's position on the planet. The receiver pinpoints (between 3 and 15 meters) where the device and thus the user is located. With multiple measurements, the receiver can also calculate speed, trip time, distance to destination, altitude, sunrise and sunset, and more.
On average, eight satellites are always within sight of wherever you are on Earth. The more satellites your GPS receiver can contact, the more accurate your readings will be.