The navigation system uses a main navigation device (2) permanently installed in the vehicle and an auxiliary navigation device (3) selectively fitted to the vehicle. The main navigation device has a memory holding map information, for calculating the actual position of the vehicle relative to the map, fed to a display device (25). The auxiliary navigation device has a secondary memory (32) in which the vehicle position can be recorded when the device is installed in the vehicle. The auxiliary navigation device is connected to the microprocessor control device (1) for the vehicle when installed in the latter and has an operating switch (36) for control of the auxiliary navigation device upon its removal from the vehicle. The positioning data are obtained through GPS receivers installed in the car.
