A method and system for determining a deviation of a vehicle from a desired course are described. The method includes receiving bearing signals from a transmitter, accessing a database, on the vehicle, to obtain transmitter position information identifying a position of the transmitter, obtaining vehicle position information using GPS identifying a current position of the vehicle, and determining a deviation of the vehicle from the desired course utilizing the transmitter position information, the vehicle position information, and the bearing signal. The system includes a receiver receiving a bearing signal from a transmitter, a database storing transmitter position information identifying a position of the transmitter, a GPS receiver obtaining vehicle position information identifying a current position of the vehicle based on a GPS signal, and a controller determining a deviation of the vehicle from the desired course utilizing the transmitter position information, the vehicle position information, and the bearing signal.