The Global Positioning System

The Global Positioning System (GPS) is the network of satellites which operates on a worldwide basis. This system allows a user to determine the exact latitude, longitude, and altitude.

All GPS satellites transmit signals in microwave part of radio spectrum, where wavelengths are a few centimeters. The signals are modulated with the special timing and identification codes. A GPS receiver allows the user to find his or her position by measuring distances to 4 different satellites. This is done by precisely timing signals as they travel between satellites and receiver. The receiver uses a computer to process the information received from satellites. From this information, it can give user an indication to within a few feet (for government and industrial subscribers) or a few hundred feet (for the civilians).

An increasing number of automobiles, trucks, and boats have GPS receivers installed. If you are driving your car in the remote area and get stranded, say in a blizzard, you may use the GPS to locate your position. By using a cell phone, you could call for help and inform authorities of your location. Someday, perhaps every motor vehicle and boat will be equipped with the GPS and wireless communications equipment.