Abstract

In an on-board navigation system for motor vehicles, having a memory device in which map data in digital form is stored, and adapted to read-out from the memory device map data of a region of a given area including a present location of the vehicle while recognizing the present location of the vehicle and to display a map on a display screen on the basis of the map data, a switching device for selectively supplying an electric power to the memory device is provided. The switching device is controlled to supply the electric power to the memory device only when the map data is read-out from the memory device. A power switch for selectively supplying the power current to a display unit is also provided, thereby further reduction of the electric power consumption is possible.