METHODS AND SYSTEMS FOR MAKING A GPS SIGNAL VITAL

摘要

Position reports from GPS receivers can be made vital through a variety of techniques including relative differential GPS corrections and a technique in which a train traveling on a fixed path is provided with a database that includes positions on fixed paths or data from which positions on fixed paths can be determined. Position reports from GPS receivers located on the vehicle are compared to the positions of the fixed paths in the database. If the distance from the position reported by the GPS receiver to the nearest point on the nearest fixed path is greater than the stated accuracy of the GPS receiver, the position report is discarded or other corrective action is taken. A second technique involves cross-checking position reports from two GPS receivers separated by a known distance, preferably mounted on a single vehicle. Still other techniques may be used.