Abstract
As the quality of the information available in the vehicle has continued to improve, timely, expansive information available by cellular phone or through a broadcast network becomes more important. Digital map download/update function is one of the desirable online services. But map data size, and low speed communications make this difficult presently. In this paper, the authors propose an efficient digital map format to reduce the size of map data. By using this new map format, map data size can be reduced to one-fourth of the present size of Japanese popular map format, without losing any information. Map data which covers approximately 1km square can now be transmitted in 3-4 seconds by 9600bps cellular phone with this new approach.