Method and apparatus of establishing a vehicle azimuth

Abstract

The method and apparatus of establishing a vehicle azimuth provides for the automatic establishment of the vehicle azimuth for a vehicle positioning mechanism, and the continued improvement of accuracy, if desired. The method and apparatus accomplishes this by obtaining an assumed initial azimuth and an actual path azimuth as the vehicle passes in the vicinity of a first beacon. The actual path azimuth can be determined as between the first beacon and a subsequent beacon further along the route, or alternatively, the first beacon can be associated with a restricted, travel path or path segment having the actual path azimuth at the exit of the maintenance garage or ferry dock. The vehicle positioning system dead reckons its position from the vicinity of the first beacon and establishes an apparent path azimuth for the vehicle over the same path having the actual path azimuth. The difference between the actual path azimuth and the apparent path azimuth is the initial offset angle. The initial offset angle corrects the assumed initial vehicle azimuth to obtain the vehicle azimuth. As the vehicle traverses more distance between the adjacent beacons or alternatively along the restricted travel path or path segment, the accuracy of the initial offset angle improves because the dead reckoning calculation becomes more accurate. Furthermore, when the vehicle passes a subsequent beacon, any ambiguity with respect to the vehicle azimuth is corrected because the coordinates of the first and second beacons or, alternatively, of two GPS positions are known, and the actual path azimuth between the two beacons or positions can be used to offset the apparent path azimuth calculated solely by dead reckoning with the assumed initial vehicle azimuth.

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