Data structure of digital map file

摘要

A terminal device for reading a cartographic file in which updating one cartographic file does not require updating cartographic files in the neighboring units. For this purpose, cartographic files which represent respective units extracted by dividing a map into a plurality of areas each comprise node records generated for respective nodes and link records generated for respective links. Given node records contain coordinate information about neighboring nodes which define connections of roads between its unit and a neighboring unit. The cartographic files are stored in a first storage device. The data processing portion executes a process of searching for a route by using the cartographic files. During the route search, the data processing portion traces the connection from a road in one unit to a road in another, neighboring, unit on the basis of the coordinate information about the neighboring nodes of said one unit and said neighboring another unit.