| 摘要 |
PROBLEM TO BE SOLVED: To reduce the receiving capacity or the receiving time by utilizing efficiently a storage device of a terminal device when acquiring map information or route guide information from a network. SOLUTION: When acquiring map data, the terminal device can select one of (1) acquisition from the network, (2) preferential acquisition from a cache, and (3) acquisition only from the cache. A map cache list is transmitted beforehand from the terminal device to a center device, and the center device receives the list and transmits to the center device only the map data not existing in the cache list among the map data required from the terminal device. When the map data existing in the cache list among the required map data exist, the acquisition times of both map data are compared. If the acquisition time of the map data in the cache list is earlier than the acquiring time of the map data in the center device, the map is transmitted from the center device. COPYRIGHT: (C)2004,JPO |
