GPS

The GPS or Global Positioning System is a navigation system which can be used throughout the world. Though it is managed by the United State Airforce at an annual cost of millions of dollars, it is also available for civilian use. It is used as an aid for navigation world wide , for making maps , land surveys and other commercial and scientific applications.

At a time, the GPS uses at least 24 satellites which are orbiting in a medium earth orbit. The microwave signals they transmit enable a GPS receiver to accurately determine the location, speed , time and direction. At a time, signals from at least 4 satellites are required by the GPS receiver. GPS signals are also used for synchronization of telecommunication networks.

The most important part of a turn by turn GPS navigation system are the routing engine and map accuracy. The major mapping data providers are NAVTEQ and TeleAtlas , with NAVTEQ providing more accurate data for North America. The routing engine differs according to the manufacturer, so 2 models have the same mapping data, may not give the same route.