| 摘要 |
A normal route guidance of a navigation apparatus based on guidance information retrieved from a hard disk drive is switched to a turn list display based on the guidance information from an external memory when a vehicle enters a high-altitude area. The navigation apparatus calculates a navigation route to a destination, and determines if the navigation route passes a high-altitude area. If the route passes the high-altitude area, the guidance information of a high-altitude area section of the navigation route is written in the eternal memory. Thus, while the vehicle is traveling, the navigation apparatus having the hard disk drive continues its navigation operation by displaying the turn list even when an operation of the hard disk drive is stopped due to a function restriction in the high-altitude area.
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