Used GPS TomTom, NavMan Sat Nav

You've come to the right place to buy a used GPS or used Sat Nav system. The GPS, typically named Global Positioning System and originally named NAVSTAR, is a satellite navigation system used for determining one's explicit location virtually anywhere on earth. A GPS unit receives time signal transmissions from assorted satellites, and generates its exact position by triangulating the information. Checkout our great deals and grab yourself a discount used GPS or used Sat Nav.

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GPS Sat Nav

The GPS normally consists of 24 satellites in 6 orbital planes. Each satellite circles the earth two times every day. The satellites hold atomic clocks and continuously transmit the exact time, along with several other administrative information. The receiver does not necessarily need a precise clock, but it needs to have contact to four satellites in order to unambiguously compute its individual latitude, longitude, elevation and the explicit time. By comparing the signals from 2 satellites, the receiver can compute the diversity between the distances to the 2 satellites. Because the receiver also understands the exact locations of the four satellites, 3 such differences allow a system of 3 (nonlinear) equations for the 3 unknown latitude, longitude and the elevation. As soon as the receivers location and therefore distance to the satellites are known, the time signal sent out by 1 of the satellites allows to compute the exact time at the receiver's location. If elevation information is not essential, only 3 satellites need to be contacted.