GPS stands for “Global Positioning System”. This satellite positioning system was originally developed by the US Army for its own purposes.
A GPS receiver is able to ascertain its position on the surface of the earth, and its height above sea level, accurate to a few metres.
To enable this, 24 satellites constantly circuit the earth on six orbits at an altitude of 20,183 km (12,541 miles). They continuously send positioning and time signals which they generate with the aid of an ultra-precise atomic clock.
GPS receivers locate the signals of up to twelve satellites simultaneously, and compare the time information received with their own in-built clocks. As the satellites are at different distances from the receiver, the signal delays are different. The GPS receiver ascertains its own location on the basis of these discrepancies. Signals are required from at least four satellites to ascertain three-dimensional results – length, height, width.
Now, the system is used for predominantly civilian purposes – first and foremost in vehicle navigation systems, but also with mobile navigation terminals. In addition, GPS is one of the accessories considered indispensable to the special security equipment of at-risk vehicles such as armoured cars, celebrity limousines, trucks with valuable or hazardous loads, etc. These vehicles can be monitored across Europe, or across the world.
GPS is also used in surveying technology, and for sports and private sailing.
