Abstract: When a narrow-angle branch point PA at which a road branches at a narrow angle gets closer, routes from the narrow-angle branch point to all points a-c reachable by traveling for a distance L after passing of the narrow-angle branch point in a current traveling direction. When the narrow-angle branch point is passed, processing to calculate, as a matching degree of each route, a matching degree between each of the gradients G1-G3 of routes R1-R3, which are indicated by map data, and history Ang of an inclination angle of a vehicle is performed until a route with a matching degree equal to or higher than a predetermined threshold is generated or until a distance L is traveled after the passing of the narrow-angle branch point. When the route with the matching degree equal to or higher than the predetermined threshold is generated, a current position is calculated on the route.

Abstract: When a narrow-angle branch point PA at which a road branches at a narrow angle gets closer, routes from the narrow-angle branch point to all points a-c reachable by traveling for a distance L after passing of the narrow-angle branch point in a current traveling direction. When the narrow-angle branch point is passed, processing to calculate, as a matching degree of each route, a matching degree between each of the gradients G1-G3 of routes R1-R3, which are indicated by map data, and history Ang of an inclination angle of a vehicle is performed until a route with a matching degree equal to or higher than a predetermined threshold is generated or until a distance L is traveled after the passing of the narrow-angle branch point. When the route with the matching degree equal to or higher than the predetermined threshold is generated, a current position is calculated on the route.