GSM location tracking is a GPS-like method of locating a cell phone or other cellular device using information about the cell phone towers with which the device is communicating. By identifying the closest tower and the relative signal strength, a tracker can estimate the general area in which a device is located. Information from multiple towers provides more specific location information.
Whenever a cell phone or other cellular device communicates through the network, it does so by establishing a radio connection with a nearby cellular tower. In many cases, the device communicates with multiple towers that are close enough to receive the signal, and selects the tower with the strongest signal to establish communication. All of these communications are recorded by the cellular network, and may be used to track the location of the device.
Because the radio communications used to establish cellular connections provide no directional information, the process of GSM tracking requires triangulation. If a phone connects with one tower strongly, the tracker can estimate its relative distance, placing it somewhere on a circle around the tower. By evaluating other signal handshakes, the system can draw similar circles around other nearby towers, eventually pinpointing the device's location where the circles meet. Since the system is not as precise as the Global Positioning System, the margin of error is usually somewhere around 50 meters.