1. A navigation system for displaying travel locations of a vehicle on a displayed map, comprising: (a) means for detecting vehicle travel angle; (b) means for detecting vehicle travel distance; (c) means, coupled to said vehicle travel angle detecting means and said vehicle travel distance detecting means, for calculating vehicle locations on the basis of the detected vehicle travel angles and distances; (d) means for storing map information data including branch points; (e) means, coupled to said map information data storing means, for setting a route judge area at each branch point to determine a route along which the vehicle travels from a branch point; (f) means, coupled to said vehicle distance detecting means, said map storing means and said route judge area setting means, for determining a condition of a vehicle passing into the set route judge area when a distance between a current vehicle location and a succeeding branch point becomes shorter than a first predetermined distance and a condition of a vehicle passing through the set route judge area when a distance between a position, at which the vehicle enters the set route judge area, and a current vehicle location becomes longer than a second predetermined distance; (g) means, coupled to said vehicle travel angle detecting means and said route judge area pass determining means, for determining a travel route at each branch point by comparing a travel angle detected by said travel angle detecting means with map data stored in said map data storing means when the vehicle has passed through the set route judge area; (h) means, coupled to said vehicle location calculating means and said travel route determining means, for correcting said calculated vehicle locations so as to be located along a road on a displayed map in accordance with predetermined expressions, said vehicle location calculating means further correcting a vehicle after-turn location at each branch point by matching a vehicle turn point obtained when said route judge area pass determining means detects that the vehicle has passed through said route judge area with a map branch point within the route judge area; and (i) means, coupled to said correcting means, said map data storing means, said route judge area setting means, and said route judge area pass determining means, for displaying a map stored in said map information data storing means and vehicle locations calculated by said calculating means and corrected by said location correcting means.