PURPOSE: To automatically switch to a map display with a small scaling factor near a destination by outputting one of data of a display memory with different scaling factor based on whether a specific position is within a measurement range or not.

CONSTITUTION: A user sets different scaling factors for VRAMs 3 and 4 via a remote controller 8. A system controller 2 reads the map data of a destination from a CD-ROM 7 and then writes them into the VRAMs 3 and 4 with a set scale factor. The user specifies a range to be switched to a screen with a small scaling factor on a screen with a large scaling factor. Then, the controller 2 writes the map data centering on the current position which is read by a position sensor 1 to the VRAMs 3 and 4 with each scaling factor. The controller 2 judges whether the current position is within a specific range or not, changes the control signal to a selector 5 and then outputs it, and then switches to (or maintains) a screen with a small scaling factor and a screen with a large scaling factor if the current position is within the specific range and outside it, respectively.