The previous knowledge of road environments is vital for driver assistance systems, and an accurate map, which provides information on the roads to be traveled, is desired. Accurate road information map preparation is still costly because a highly accurate positioning system and manual mapmaking operations are required. This paper proposes a method for automatic high accuracy map generation at low cost, using a standard in-vehicle camera and a standard GPS. The positioning results from GPS have relatively large error, so that the accuracy of a map based on these positioning results is not adequate. Our proposed method enables accurate map generation of a local area by a vehicle, and improves global accuracy by optimal integration of many local maps. This paper describes accurate local map generation based on precise trajectories derived from GPS Doppler, and evaluates the effectiveness of this method using actual data.