US Patent 7680593 Map data updating method

An information center has an all-road updating data and a main-road updating data. The all-road updating data is a difference of all roads extracted from an all-road map data, and the main-road updating map data is a difference of specified roads extracted from the all-road map data. A map display system executes a reverse-updating to return the map data to a previous state not updated with the main-road updated map data, when its map data has already been updated with the main-road updated map data. The map display system then executes updating of the map data with the all-road updated map data.