1. A system for determining an estimate of the position of a vehicle based on pseudoranges derived from a vehicle positioning system and prior position estimates, the system comprising: (a) first means for receiving signals from a plurality of satellites, responsively determining respective pseudoranges from said satellites to the vehicle, and deriving a first position estimate of the vehicle's position as a function of said pseudoranges; (b) second means responsive to said first means for receiving the prior position estimates and responsively determining a vehicle path model using a best fit algorithm; (c) third means responsive to said second means, said third means for extrapolating a second position estimate from said vehicle path model; and (d) fourth means responsive to said third means, said fourth means for setting said first position estimate equal to said second position estimate if said second position estimate is more accurate.