Global Positioning System (GPS) works based on a technology called trilateration, calculating location, velocity and elevation. Trilateration collects signals from satellites to provide location information. GPS satellites circle the Earth twice a day in a precise orbit. Each satellite broadcasts a unique signal and orbital parameters that allow GPS devices to calculate the precise location of the satellite
When a satellite sends a signal, it creates a circle with radius, based on the measured distance from the GPS device to the satellite. By adding 2nd satellite, we will have another circle, which creates two points where circles intersect. The 3rd satellite creates another circle, which helps to determine the device’s location. The 4th satellite is used to validate the accuracy of the information.
The information from satellites is defined by the GPS device. In order to determine a location on earth, the device needs to read the signal from at least 3 satellites. And because each satellite circles the earth twice a day, that means a GPS device can get the signals from six or more satellites.
GPS receivers are programmed to receive information about where each satellite is at any given moment. A GPS receiver use this information and trilateration to calculate a location. Because radio waves travel at a constant speed, the receiver can use the time measurements to calculate its distance from each satellite.