Map database generation system for in-vehicle navigation system

In order to implement the accuracy and detailed map database with wide area coverage, the database should be compact in size and must be created efficiently and automatically, at low cost. We developed a software system to resolve these problems. With this system, we first make an original map database by enhancing road data from the Japan Digital Road Map Association, and add other important information such as facilities and traffic restriction information. Then, according to the display scale of each map, adequate road details, background, and character information is selected and extracted from the original database. Layouts of character information are determined automatically according to the priority of each item of information and spacing between each character. In this way, a map database can be automatically generated at less than one third the size of the original database. As a result, map data of the whole area of Japan can be stored in a CD-ROM disc. This paper describes the data compression method and an automated conversion algorithm of map data into a compressed format