| 摘要 |
It is determined whether an access to a map database is possible. When the access is possible, a route to an entry point designated by a user is constantly retrieved; then, route information relating to the retrieved route is stored. In contrast, when the access is impossible because of malfunction of the map database, a route guidance to the entry point is performed using the stored route information. This enables a route guidance to a point where the user wants to go even when the access to the map database becomes disabled.
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