Route exploration method of navigation apparatus

Abstract

In a navigation apparatus for setting a route from a designated departure point to a destination and providing guidance along the route, there are provided, as map data used in route exploration, node data [FIG. 15(b)] comprising position information and information relating to the attributes thereof, intersection data [FIGS. 2-5(b), FIG. 15(b)] comprising information relating to intersections, and road data [FIGS. 2-5(a), FIG. 15(c)] comprising information related to roads. Information such as roads between intersections and intersections which are the starting and end points of roads are obtained from the intersection data and road data, and an optimum route is retrieved by comparing routes. The map data is put into the form of a layered structure, as shown in FIG. 1, a branch road network is developed in an upper-layer (2) connected to a trunk road network with respect to a higher-order layer (1) of the trunk road network, block division is performed, and exploration from a lower-order layer to intersections connected to a road network of the higher-order layer is successively repeated. The foregoing makes it possible to perform processing upon limiting the range of exploration, and to raise the speed of exploration processing. In addition, the work area needed for exploration can be reduced and storage data can be conserved.