GPS--- -------- It is a system which shows the exact position on the Earth,anytime,anywhere,in any weather conditions.It works with the help of a number of GPS satellites orbiting the Earth.The receiver accepts the signals from the satellites,and determines position with great accuracy.We can hold the receiver in our hand,or in a moving vehicle like a car,to get the information. Each satellite is equipped with precise clocks that keep accurate time.These time signals are transmitted with other parameters,to the receiver.The receiver detects the signals from three satellites,and by doing mathematical calculations, its location is accurately determined.By getting the information from a fourth satellite,it is able to give the time also.Thus,at a time a minimum of four satellites are visible to the receiver.
