| 摘要 |
A navigation device includes a GPS receiver, map data including tunnel data and periodically acquires a vehicle's speed to provide guidance on the current position N acquired at the GPS receiver, and when GPS radio waves become unreceivable after the vehicle passes a tunnel entrance, calculates a travel distance according to a vehicle speed and a time T up to a branch, and continues providing guidance on the current position up to the branch. After passing the branch, the navigation device suspends guidance, calculates a distance La between the branch and a tunnel exit, which is shorter, and when GPS radio waves are not received even after a movement distance from the branch exceeds distance La, after passing the branch, determines a road whose distance is longer as the road being traveled, and provides guidance on the current position. |
| 主权项 |
1. A terminal device that provides guidance corresponding to a current position on map data, characterized by comprising:
map data storage for storing the map data; current position acquiring module for receiving radio waves from GPS satellites and acquiring a current position on the map data; blocking area acquiring module for acquiring a blocking area in which radio waves from the GPS satellites are not receivable, the blocking area corresponding to the map data; guidance module for providing guidance corresponding to the current position, and in a case in which the terminal device is moving on a road in the blocking area and the road has a branch, suspends the guidance corresponding to the current position; physical amount estimating module for estimating a physical amount in the blocking area, the physical amount being convertible to a movement distance; and movement road determining module for determining a road on which the terminal device is moving after the branch in the blocking area, on the basis of the estimated physical amount and a reception condition of radio waves from the GPS satellites. |
