Satellite navigation for vehicles

The position of a vehicle 210 is determined using GPS satellites 102. In the one embodiment, a plurality of antennas (402, Fig 7) are mounted on the vehicle 210. The distance between the antennas (402) is precisely known. The distance used in conjunction with the received signals to improve the accuracy of the position estimate or to allow operation with a reduced number of satellites. Either a single receiver or one receiver per antenna may be used. In another embodiment (Fig 8), a plurality of base stations of known position each transmits to the vehicle pseudorange data, which the vehicle uses to obtain a corresponding plurality of corrected positions using differential GFS techniques; these are used to provide ranges to corresponding base stations, and a finally corrected vehicle position is then determined by trilateration from the base stations. The resultant positions may be combined with INS (318, Fig 3) desired positions to further improve accuracy, and may be Kalman filtered.