METHOD AND DEVICE FOR JUDGING PRESENCE OR ABSENCE OF CITY MAP IN NAVIGATION DEVICE, AND MAP DATA STORAGE

摘要

PROBLEM TO BE SOLVED: To accurately judge whether a city map at its own vehicle position exists or not and to make displayable the city map according to request or automatically by equipping a polygon for surrounding a region where the city map exists and cornaring and judging whether its own vehicle position or the judgment position of a display screen is within the region of the polygon or not.;SOLUTION: A map data part 14 consisting of CD-ROM and DVD-ROM devices is provided with polygon data for surrounding a region where a city map corresponding to each block of map data exists. Also, a control part 17 accurately judges whether the city map at the current own position or display position exists or not using the polygon data and automatically and accurately displays the city map according to user's instructions accordingly. The current own position is detected to judge whether the own vehicle position is within the polygon region for surrounding a region where the city map exists or not. If the current own position exists in the polygon region, the display button of the city map is displayed. The city map corresponding to a navigation device is displayed when the button is pressed.;COPYRIGHT: (C)2000,JPO