Navigation system and path search method

Claim 2

A navigation system as defined in claim 1, wherein said path search means makes the path search in such a way that nodes connecting with the roads in higher ones of said hierarchies and paths extending to the nodes are searched for from the point of departure and from said destination point, sequentially in the respective hierarchies from the hierarchies corresponding to said point of departure and said destination point up to the hierarchy corresponding to a distance between said point of departure and said destination point, the connecting nodes and the extending paths being searched for as to each of said respective hierarchies and on the basis of the road data of the pertinent hierarchy relevant to at least one of said management areas as lies within the limits having the size which corresponds to said pertinent hierarchy, and that a path is searched for between the nodes which have been searched for and which connect with said roads in said hierarchy corresponding to the distance between said point of departure and said destination point.

Claim 3

A navigation system as defined in claim 1, wherein: said path search means searches for a node connecting with the road in that one of said hierarchies which is directly higher than the hierarchy corresponding to said current point, and a path extending to the node, from said current point, before said destination point is accepted by said set input means, and it searches for said path extending from the point of departure to said destination point, under a condition that said node connecting with said road in the directly higher hierarchy is set as said point of departure, after said destination point has been accepted; and said guidance means guides the running of said vehicle on the basis of the path which extends to said node connecting with said road in said directly higher hierarchy and which has been searched for by said path search means, immediately after said destination point has been accepted.

Claim 4

A navigation system for installation on a vehicle, comprising: storage means for storing therein road data of roads which belong to management areas, for each of the management areas being geographical areas of predetermined extent and shape and for each of hierarchies corresponding to sorts of roads; positioning means for detecting a current point and a traveling direction of the vehicle; set input means for accepting setting of a destination point; path search means for searching for a path which extends from a given point of departure to the destination point; and guidance means for guiding running of said vehicle on the basis of the current point measured by said positioning means and the path searched for by said path search means; said path search means setting candidate areas to-be-searched sequentially in higher ones of said hierarchies from the hierarchy which corresponds to the point of departure, under a condition that the higher hierarchies have larger sizes, until said destination point is contained in any of the candidate areas to-be-searched; then setting a search area to-be-searched in correspondence with the limits of the candidate area which contains said destination point; and subsequently making the search for said path on the basis of those road data of said candidate area which are relevant to at least one of the management areas as lies within the search area.

Claim 5

A path search method, comprising: classifying roads into a plurality of hierarchies in correspondence with sorts of the roads, and managing road data of said roads which belong to management areas, for each of the management areas being geographical areas of predetermined extent and shape and for each of the hierarchies; setting a point of departure as a first search starting point, setting as a first search hierarchy to-be-searched the hierarchy in which the road nearest the first search starting point is contained, and setting as a first candidate search area to-be-searched those limits around said first search starting point which correspond to the first search hierarchy; searching for a path which extends onto the road belonging to the hierarchy directly higher than said first search hierarchy, on the basis of the road data of said first search hierarchy relevant to said management areas as lies within the first candidate search area, on condition that a destination point is not contained in said first candidate search area, the path search being sequentially made until the destination point is contained in said first candidate search area; whereupon an end point of the path searched for is set as a renewed first search starting point, said hierarchy directly higher than said first search hierarchy is set as a renewed first search hierarchy to-be-searched, and those limits around the renewed first search starting point which correspond to the renewed first search hierarchy is set as a renewed first candidate search area to-be-searched; setting said destination point as a second search starting point, setting as a second search hierarchy to-be-searched the hierarchy in which the road nearest the second search starting point is contained, and setting as a second candidate search area to-be-searched those limits around said destination point which correspond to the second search hierarchy, on condition that said destination point is contained in the set first candidate search area; setting as a real search area to-be-searched an area into which said first candidate search area and the second candidate search area are smoothly joined; and executing a process in which a path extending between said first search starting point and said second search starting point is searched for on the basis of said road data of said management areas contained in the real search area, and subsequently connecting the path searched for in the process with the first-mentioned path searched for before, thereby obtaining a path which extends from the point of departure to said destination point; the first and second candidate search areas in the higher hierarchy being set at limits of a larger size than in the lower hierarchy.

Claim 6

A path search method as defined in claim 5, wherein said process in which the path extending between said first search starting point and said second search starting point is searched for on the basis of said road data of said management areas contained in said real search area, comprises: searching for a path which extends onto the road belonging to the hierarchy directly higher than said first search hierarchy, on the basis of the road data of said first search hierarchy relevant to said management areas as lies within the first candidate search area, on condition that said first search hierarchy is lower than said second search hierarchy, the path search being sequentially made until a final search hierarchy to-be-searched which is said second search hierarchy is reached; whereupon the end point of said path searched for is set as the renewed first search starting point, said hierarchy directly higher than said first search hierarchy is set as the renewed first search hierarchy to-be-searched, and those limits around said renewed first search starting point which correspond to said renewed first search hierarchy is set as the renewed first candidate search area to-be-searched; searching for a path which extends onto the road belonging to the hierarchy directly higher than said second search hierarchy, on the basis of the road data of said second search hierarchy relevant to said management areas as lies within the second candidate search area, on condition that said second search hierarchy is lower than said first search hierarchy, the path search being sequentially made until a final search hierarchy to-be-searched which is said first search hierarchy is reached; whereupon the end point of said path searched for is set as the renewed second search starting point, said hierarchy directly higher than said second search hierarchy is set as the renewed second search hierarchy to-be-searched, and those limits around said renewed second search starting point which correspond to said renewed second search hierarchy is set as the renewed second candidate search area to-be-searched; and searching for the path which extends between said first search starting point and said second search starting point, on the basis of those road data of the hierarchy higher than the final search hierarchy which ore relevant to said management areas contained in said real search area.