This invention extends GPS coverage in an automotive environment without requiring direct interfaces to the vehicle's sensors in a unique and cost effective way. Since it removes all required vehicle interfaces (except power), it produces a virtually portable navigation system with no installation requirements beyond that of the GPS receiver itself. It also removes the necessary "customization" of the navigation system to each particular vehicle. Fundamentally, the position of a vehicle is obtained by GPS receiver data augmented with a low cost gyro whereby the gyro accurately tracks the heading changes of the vehicle (in the absence of sufficient GPS information), and the GPS receiver includes an innovative algorithm for deriving speed information from Doppler measurements from just one or two GPS satellites.