A system includes a global positioning system receiver to determine position of a railroad vehicle, a predetermined track map of possible coordinates of the vehicle, motion sensors providing a positive bias error to determine change in location of the vehicle, an acceleration sensor to determine acceleration of the vehicle, and a processor to vitally determine the location and the location uncertainty of the vehicle on the track map. The processor verifies one motion sensor with another motion sensor, determines a slip or slide condition of the vehicle from one of the motion sensors, determines speed and position of the vehicle from the acceleration sensor during the slip or slide condition, verifies the position of the vehicle from the global positioning system receiver based upon the track map, and corrects the positive bias error of the motion sensors using the position of the vehicle from the global positioning system receiver.