Patent ID: 6633814
Filing Date: 2003-10-14
Classification: G01C,G01S,H04B,H04L

Abstract:
A GPS system for navigating a vehicle, comprising:means for tracking at least one GPS satellite to provide on-track information related to a position of the vehicle along a selected track; means for using data, including the on-track information, to generate a position model for the vehicle comprising a time estimate, test, an altitude estimate, zest, a track estimate, aest, and a cross track estimate, cest, wherein the track estimate indicates an estimated position on an axis parallel to the selected track in a plane and the cross track estimate indicates an estimated position on an axis perpendicular to the selected track in the same plane; means for determining a predicted track based on information including at least the current heading of the vehicle, the predicted track at least initially corresponding to the selected track; means for updating the position model; and means for providing vehicle navigation data from the position model, including means for providing vehicle navigation data during a period when less than four satellites are in view, including holding at least one of the altitude estimate, the time estimate, the track estimate and the cross track estimate at a current value during the period.