Patent ID: 6892132

Claim:
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, wherein the map data includes data units respectively corresponding to a plurality of map display elements, and the data units are given respective priority levels, the communication navigation system comprising: a transmitting device in each of the navigation terminals which transmits request information including priority levels which are determined based on the order in which map display elements are displayed by the respective navigation terminal; a receiving device in the map database site which receives said request information from one or more of the navigation terminals; a transmitting device in the map database site which transmits data units for all map display elements for a map to the one or more navigation terminals via the communication network, the data units being transmitted according to the respective priority levels included in received request information; a receiving device in each of the one or more navigation terminals which sequentially receives the data units transmitted from the transmitting device; and a displaying device in each of the one or more navigation terminals which sequentially displays on the map the map display elements respectively corresponding to the data units received by the receiving devices, wherein even if all the data units for the map display elements needed for the map are not received, the displaying device displays a map based on the data units for the map display elements that are received.