Abstract: Navigation systems, methods, and programs acquire deviated point information regarding a deviated point where a vehicle traveling a set route has deviated the route, and acquire post-deviation travel history information regarding a travel history after a deviated vehicle has deviated the route at the deviated point. The systems, methods, and programs determine based on the post-deviation travel history information for each of the deviated vehicles whether the deviated vehicle has traveled along a reroute set after deviating the route at the deviated point, and judges whether a rate of the deviated vehicles which were determined as having traveled along the reroute is a first predetermined value or more. If the rate of the deviated vehicles which were determined as having traveled along the reroute is the first predetermined value or more, the systems, methods, and programs determine that guidance of the route is not appropriate.

Abstract: A method that can locate the center of a target even when the target is a large vehicle, and that, when a plurality of beams are reflected, determines whether the reflected beams are from the same target or not, wherein, of peaks generated based on a radar signal reflected from the target, peaks whose frequencies are substantially the same and whose reception levels are not smaller than a predetermined value are selected and, when a plurality of such peaks are selected, a center angle between the angles of the leftmost and rightmost peaks is obtained, and the thus obtained center angle is taken as an angle representing the target. Further, the plurality of peaks are paired up to detect a distance, relative velocity, and displacement length for each of reflecting points on the target, and when the differences in these values are all within respectively predetermined values, the plurality of peaks are determined as being peaks representing the same target.