A GPS tracking device empowers a person using it, to precisely locate a vehicle or person or any thing that it is attached to. It makes use of the Global Positioning System to record and store the position within the device. The information may also be transmitted to a central location database via a cellular (GPRS), radio, or satellite modem installed in the tracking unit. GPS is the only fully-functional satellite navigation system that encompasses more than two dozen GPS satellites. The technology of pinpointing the position is straight-forward. The GPS receivers measure the time delay between when the satellite sent the signal and the exact local time when the signal was received. The delay is then multiplied by the speed of light and distance to that satellite is recorded. The position of the satellite is also calculated and compared to the distance. Eventually, the location of the receiver is obtained. The location is given in terms of longitude, latitude and altitude and can be determined in any weather and on any place on Earth. There are various types of GPS trackers available. One tracker has the capability of sending the exact coordinates through instant text messaging by SMS. A stolen car can be tracked down using this tracker, as it automatically maps the vehicles speed and location with tracker. There are also many special tracking devices available for vehicles, which are little bulky, however the personal ones are lighter. The GPS tacking device is useful even in scientific research, for study of earth-borne calamities, map-making and survey of land. GPS has now become an indispensable part of navigating in air, water, or land.