The Global Positioning System, or GPS, consists of 30 specialized satellites that orbit the globe at over 10,000 miles above the Earth’s surface continuously transmitting information towards the earth. This information can be "detected" by GPS receivers. A GPS receiver, combined with a small computer, can calculate it's lat/long (latitude and Longitude). The current GPS system is accurate to within about a meter.

Although the GPS system was deployed in the 1970s exclusively for military use, today GPS receivers are used by millions of people of private citizens around the globe for business and recreation. One of the most common commercial uses of GPS is Vehicle Location.

In this application, a GPS receiver is installed into a vehicle where it constantly monitors the GPS information being sent from the satellites. The GPS unit continually stores new information coming from the GPS satellites so that someone, usually in a home office, can monitor in real-time, the location of the vehicle. GPS systems also include built-in clocks so that the system can calculate additional information such as how far a vehicle has traveled, how long it has been moving, when it started, when it stopped, and how fast the vehicle is moving at any particular time. This information can be stored indefinitely on a computer, so that a history of a vehicles movements is easily accessible.

Marcus 6 Radio Module	Marcus GPS Receiver and Cable

Shown above are two pieces of the Marcus v6 GPS Automatic Vehicle Location System - The Marcus Radio Module, and the GPS receiver.