Patent ID: 9157753
Filing Date: 2015-10-13
Classification: G01C

Abstract:
1. A navigation system mounted in an automobile to calculate a current position of the automobile, comprising: a storage unit configured to store map data indicating a two-dimensional map in longitude and latitude and a gradient of a road; an inclination angle calculation unit configured to detect an inclination angle of the automobile; a measurement unit configured to measure a position in longitude and latitude directions of the automobile; and a current position calculation unit configured to perform first current position calculation processing to calculate a position on the road as a current position by map-matching between a position measured by the measurement unit and the two-dimensional map in longitude and latitude indicated by the map data, wherein when the current position passes a narrow-angle branch point which is a branch point at which the road branches at a narrow angle, the current position calculation unit is configured to calculate all routes which can be traveled after the passing of the narrow-angle branch point in a current traveling direction, and after the passing of the narrow-angle branch point, the current position calculation unit is configured to stop the first current position calculation processing and to start second current position calculation processing, wherein the second current position calculation processing is processing to calculate a degree of certainty of each route as a route currently traveled according to a matching degree between a gradient of each route indicated by the map data and the inclination angle detected by the inclination angle calculation unit until a degree of certainty equal to or higher than a predetermined level is calculated in respect to any of the routes, and to calculate a position on a route, in which the degree of certainty equal to or higher than the predetermined level is calculated, as the current position when the degree of certainty equal to or higher than the predetermined level is calculated in respect to any of the routes, and when there is a different branch point in a position, within a predetermined distance from the narrow-angle branch point, on a road branching at the narrow-angle branch point, all routes include a plurality of routes which goes to the different branch point from the narrow-angle branch point and respectively goes to a plurality of roads branching at the different branch point.