The Gps Technology Essay

1978 Words Feb 10th, 2013 8 Pages


Throughout time people have developed a variety of ways to figure out their position on earth and to navigate from one place to another. Early mariners relied on angular measurements to celestial bodies like sun and stars to calculate their location. The 1920s witnessed the introduction of more advanced technique-radio navigation-based at first on radios that allowed navigators to locate the direction of shore-based transmitters when in range. Later development of artificial satellites made possible the transmission of more precise, line of sight radio navigation signals and sparked a new era in navigation technology. Satellites are first used in position finding in a simple but reliable 2D Navy
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Time synchronization between the GPS receiver and the on-board clocks is very important. Then only the Ranging calculations can be done accurately. The satellite transmitter and the Earth station receiver produce identical synchronizing (pseudorandom) codes at exactly the same time. This time will be accurate up to a few nanoseconds. Each satellite continuously transmits its precise synchronizing code. After a synchronizing code is acquired, the receiver compares the received code with its own locally produced code to determine propagation time. The time difference multiplied by the velocity of radio signal gives the distance to satellite.

If the Earth station receiver knows the location of the single satellite and the distance the satellite is from the receiver, it knows that it must be located somewhere on an imaginary sphere centered on the satellite with a radius equal to the distance the satellite is from the receiver. If the receiver knows the location of the two satellites and their distances from the receiver, it can narrow its location to somewhere on the circle formed where the two spheres intersect.
If the location and distance to a third satellite is known, a receiver can pinpoint its location to one of the two possible locations in space. If the location and distance from a fourth satellite is known, the altitude or the 3D position of the Earth station can also be

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