GPS (Global Positioning System) is a system to tell the location coordinates (X, Y, Z) by speed and time The receiver uses messages received from satellites to determine the satellite positions and time sent. The GPS concept is based on time and the known position of specialized satellites. The working principle of From GPS satellites orbiting around the Earth signal back to the receiver of the surrounding world. Such as telephone, mobile and car.

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http://wut007.blogspot.com/2012/07/gps.html