How Does a GPS Car-Tracking System Work?

What is a Car GPS Tracking System?

The Global Positioning System (GPS) is currently the only functioning satellite-based navigational system in the world. It consists of a network of 2 to 3 dozen satellites. While other countries (Russia, the European Union, India and China) are all working on competing systems, none are operational as of yet.

What Does it Do?

A GPS receiver monitors microwave signals from the orbiting satellites. These signals contain the time of transmission and the position of the satellite. The receiver analyzes these signals by using the travel time of the signals and positions of the transmitting satellites to trilaterate its position. At least four signals are necessary for a good position lock using the GPS system.
In an automotive-based GPS system, this GPS coordinate data is fed into the unit's database of road information, indicating your location on a stored map. This database and location information is also usually analyzed to provide directions to a set destination. Typical car GPS systems also receive data from the speedometer (speed gauge) for greater accuracy in positioning.

Difficulties

Since the GPS signals are relatively weak, many forms of electromagnetic interference can disrupt one or more of the necessary microwave transmissions. In nature, solar flares and other magnetic events can disrupt the signals. There are two problems that are particular to car-tracking systems. Metal parts in automobiles, such as the frame plus the wires of a defroster, can combine to form a Faraday Cage that blocks out the signals. Finally, there are man-made jamming devices. Also, car-tracking systems lose their signal whenever they enter a tunnel or even go under an overpass.