A first navigation system is provided with: a present position detecting
device (16, 17) for detecting a present position; a plurality of memory
devices (14, 15) each capable of reading out map data which is recorded
therein; a navigation controlling device (11) for controlling a navigation
operation in correspondence with the detected present position by using
the map data; and a map data reading device (11) for accessing one of the
memory devices, which is selected in accordance with a predetermined
condition, and reading out the map data required for the navigation
operation therefrom.
