The Global Positioning System (GPS) is a US defense initiative that is capable of calculating with accuracy the geographical position of any GPS enabled target anywhere in the world at any given time.
The GPS system consists of 24 satellites that orbit the earth. These satellites are geo-synchronous and maintain exactly the same position with respect to the earth below them. All the GPS satellites transmit radio signals, which are then captured by a GPS receiver and used for calculating its geographical position.
GPS receivers convert signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (latitude, longitude and elevation) and Time. GPS receivers are popularly used for navigation, positioning, time dissemination, and other research.
Simply put a GPS enabled device (a vehicle for example) can be tracked at any time to a distance of a few meters anywhere in the world!
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