The Global Positioning System or GPS is a navigational system, which uses satellites and computers to determine position of a receiver on Earth. The G PS is the only satellite navigation system that is fully functional. It is a constellation of twenty-four satellites. These satellites radio signals to electronic GPS receivers. By doing so the satellites are able to find the correct location of the receivers. They get the exact longitude, latitude and altitude of the receiver. It works day and night and in all weather conditions. GPS was declared fully functional in 1985. GPS is used for navigating on land, sea and air. It is also used for research and information on topography.Availability of better and cheaper GPS devices has led to extensive usage of GPS systems. A handheld GPS can be any small handheld device like a wristwatch or radio. GPS system helps by showing the way or the map of the area where a person is. It prevents the individual form getting lost in an unknown area. It gives the current location of the holder and also information on the surrounding area. The GPS user can get information about the area a person is in. For example, the place where he is currently at, the nearest hotel, petrol pump, hospital and so on. GPS watches can be fitted with a GPS receiver, which relays a signal to a central command center equipped with GPS software systems. The system can track the position of the wearer and transmit the information. A variety of such GPS phones and wristbands are now sold in the market. They are useful to mountain climbers and hikers.GPS is one of the most useful technologies that has been developed in recent years. The accuracy of the GPS signal has improved steadily for the past 15 years and is expected to improve further. This can be achieved by using techniques such as differential GPS. GPS also gives an extremely precise time reference. Improvement in GPS systems will lead to further improvement in the field of navigation and others related to travel and surveilance.