Geographic database

摘要

A geographic database for use with a navigation application program that provides navigation features to an end-user. The geographic database includes data entities that represent segments of roads and additionally includes data entities that represent aggregations of segments of roads. The data entities that represent aggregations of segments of roads are used during a route calculation by the navigation application to suppress evaluation of roads of lesser functional rank thereby enhancing performance of the navigation system. According to one aspect, each of the data entities that represent segments of roads that represents a segment of a road that together with at least one other segment of a road forms part of an aggregation which is represented by one of the data entities that represent aggregations of segments of roads includes a reference thereto. According to another aspect, each of the data entities that represent aggregations of segments of roads refers to data entities that are abbreviated representations of the segments of roads included in the represented aggregation. Each of the data entities that are abbreviated representations of the segments of roads refers to a corresponding one of the data entities that represent segments of roads that represents the same respective segment of road. According to this aspect, at least some of the data entities that represent aggregations of segments of roads are stored separately from the data entities that are abbreviated representations of the segments of roads included in the represented aggregation. According to a further aspect, the navigation application program uses the references between the data entities that represent segments of roads, the data entities that represent aggregations of segments of roads, and the data entities that are abbreviated representations of the segments of roads included in the represented aggregation to provide navigation features, including evaluating which data entities to use for route calculation and ascertaining whether a solution route has been found.