A communication navigation system that performs navigation, using map data stored
in a map database site and current position data about navigation terminals, by
transmitting the map data to the navigation terminals via a communication network
such as the Internet, wherein the map data includes data units respectively corresponding
to a plurality of display elements for display on a map, and the data units are
given respective priority levels. The map database site is provided with a server
for transmitting the data units via the communication network according to the
respective priority levels. Each navigation terminal is provided with a transmitter/receiver
for sequentially receiving the data units transmitted from the server, and a display
subsystem for sequentially displaying the display elements respectively corresponding
to the data units received by the transmitter/receiver, on the map.
