tailieunhanh - Understanding the GPS P2

How the Global Positioning System works is, conceptually, really very simple. All GPS is, is a distance (ranging) system. This means that the only thing that the user is trying to do is determine how far they are from any given satellite. There is no inherent vector information, which implies azimuth (compass direction) and elevation, in the GPS signal. All that the GPS satellite does is shoot out a signal in all directions, although there is a preferential orientation towardthe Earth. In essence, the GPS operates on the principle of trilateration. In trilateration, the position of an unknown point is. | Ho wDoesGPSWorkrX GPS Is A Distance Ranging System Operates On The Principal Of Trilateration Satellites Transmit Unique Radio Waves Receivers Passively Receive SV Signal Receivers Meas. Time For Signal To Reach It Distance Computed by D V x Ta V C 300 000 Km Sec 186 000 Mi Sec How Does GPS Work How the Global Positioning System works is conceptually really very simple. All GPS is is a distance ranging system. This means that the only thing that the user is trying to do is determine how far they are from any given satellite. There is no inherent vector information which implies azimuth compass direction and elevation in the GPS signal. All that the GPS satellite does is shoot out a signal in all directions although there is a preferential orientation towardthe Earth. 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 . 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. The satellites do this by transmitting a radio signal code that is unique to each satellite. Receivers on the ground passively receive each visible satellite s radio signal and measures the time that it takes for the signal to travel to the receiver. Distance is then a simple matter of computing D V x T or deriving distance D by multiplying the time in transit T of the signal by the velocity of transit V . This is the old if a car travels a 60 mph how far will it travel in two hours Since radio waves travel at the speed of light which is essentially fixed at 300 000 kilometers per second the velocity is a given. Therefore the only thing needed by the user to calculate distance from any given satellite is a measurement of the