| 摘要 |
PROBLEM TO BE SOLVED: To enable a road now in use after branching off to be specified even when the road now in use branches off in a cut-off region such as a tunnel and the like unable to receive a radio wave from a Global Positioning System (GPS) satellite.SOLUTION: A navigation device comprises: a GPS receiver; and map data that includes tunnel data. The navigation device is configured to: periodically acquire a vehicle speed by a wired line or radio from a vehicle; guide a current position N acquired by the GPS receiver; when the vehicle cannot receive a GPS radio wave after passing an entrance I of the tunnel, calculate a running distance L to a branch point P from the vehicle speed to be acquired from the vehicle and a time T; continuously guide the current position N up to the branch point P; after passing the branch P, stop the guide; calculate a distance La short in a distance up to a tunnel exit; and, when the GPS radio wave is not received even if a movement distance from the branch point P exceeds the La, after passing the branch point P, specify a road B long in the distance up to the tunnel exit as a road now in use to guide the current position. |
