Abstract: Disclosed is a navigational system for accurately determining the position of a vehicle, such as a boat, truck, automobile or airplane in relation to two or more commercial AM radio transmission antenna or other signal sources of known longitude and latitude. The frequencies and exact coordinates (longitude and latitude) of the radio antenna are entered by keyboard input into the memory of the system. The null angles from the vehicle to the radio antenna are determined automatically by a computer controlled radio direction finder antenna mounted on the vehicle. The heading of the vehicle is determined and the relative null angles (in relation to the heading of the vehicle) are converted to standard null headings (North, 0.degree.) by the system. The known positions of the stations are automatically compared by the system to the respective true and false (180.degree.