Abstract: A navigation system comprises a vehicle position sensor for monitoring and updating vehicle position, a travel distance sensor monitoring vehicle travel distance, a memory means for storing position data of update points, distances between successive update points, and preset direction of travel of the vehicle at update points, an update zone setting means, responsive to a signal from the vehicle position sensor indicating that the vehicle has reached an update point to within a given range depending upon the distance between the last two update points, for comparing travel distance measured by the travel distance sensor and the distance between said two update points to derive the difference therebetween, and setting an update zone around the next update point based on the derived difference, and a detector means responsive to said signal from the vehicle position sensor for monitoring the direction of travel of the vehicle within the update zone and recognizing that the vehicle is at the update point when t