outdoor navigation in network

OUTDOOR NAVIGATION USING GPS
The best way to know where you are is by using the global positioning satellite (GPS) constellation of satellites, a collection of at least 24 satellites orbiting 26,560km above the Earth. Ignoring blockage from mountains, buildings, and such, three satellites are guaranteed to be visible from most places of the Earth, enough to closely approximate our latitude and longitude. Four or more satellites are usually visible, enough to determine the position in three dimensions. Since the UERE of the GPS is about 6 meters (approx.), the accuracy can do well with the outdoor navigation. In essence, the GPS operates on the principle of trilateration. In trilateration, the position of an unknown point is determined by measuring the lengths of the sides of a triangle between the unknown point and two or more known points (i.e., the satellites). This is opposed to the more commonly understood triangulation, where a position is
determined by taking angular bearings from two points a known distance apart and computing the unknown point’s position from the resultant triangle. Therefore, the only thing needed by the user to calculate distance from any given satellite is a measurement of the time it took for a radio signal to travel from the satellite to the receiver. By this method, the GPS unit get the latitude and longitude location of the users position. Then this coordinates is given to coordinate locater which has a inbuilt map in it the coordinate locater superimposes the coordinates on the map and find the location where the user is and returns it back to GPS unit. Since the voice signals are generated in the GPS unit and directly fed into the voice amplifier. The GPS unit will read the location aloud so that blind people can able to navigate their path.