Patent ID: 7756634

Claim:
A navigation device for a motor vehicle that calculates a current position, the navigation device comprising: a map-data-storage unit storing map data defining a map including a road by using at least one link which is a line; a vehicle-speed-measuring unit to measure a speed of the motor vehicle; an angular-velocity-measuring unit to measure an angular velocity of a change in a travel azimuth of the motor vehicle; and a current-position-calculation unit to calculate the current position of the motor vehicle, wherein the current-position-calculation unit includes: a curvature-estimation unit to estimate a road curvature at a first point on a road, the first point corresponding to a second point on the link, as a corresponding curvature of the second point on the link on the basis of the map data stored in the map-data-storage unit, where the corresponding curvature is estimated for each of a plurality of the second points on the link indicating a road on which the motor vehicle is traveling, the road including the current position that was previously calculated; a start-point-corresponding-position-calculation unit to calculate the second point corresponding to a start point of a road-curve section where an orientation of the actual road changes, as a curve-section-start-point-corresponding position, on the basis of the estimated corresponding curvature of each of the plurality of second points on the link; and a current-position-estimation unit to detect that the motor vehicle enters the road-curve section when a first change occurs in a curvature of a travel locus of the motor vehicle, the travel locus being calculated on the basis of a progress of the measured vehicle speed and angular velocity, where the first change matches with a second change in the corresponding curvature, the second change being caused when the motor vehicle travels on the link from outside a first section that is on the link and that corresponds to the road-curve section, passes the curve-section-start-point-corresponding position, and enters the first section, and that is configured to estimate the calculated curve-section-start-point-corresponding position as the current position when it is detected that the motor vehicle enters the road-curve section.