Method and system for forming a database of geographic data for distribution to navigation system units

DETAILED DESCRIPTION To address these and other objectives, the present invention comprises a method for forming a geographic database that can be used in a navigation system in which geographic data are transmitted in portions, as needed, from the geographic database to remotely located end users' computing platforms and used by the remotely located end users' computing platforms to provide navigation-related services and features to the end users as the end users travel along roads in a geographic region.
The method includes the step of forming a plurality of separate collections of data from a primary copy of the geographic database.
Each separate collection includes data that represent all roads of a corresponding respective separate rank, wherein a rank of a road represents a functional classification of the road such that roads that permit generally faster travel have a higher rank than roads that permit generally slower travel.
The method further includes the step of augmenting each of the plurality of separate collections with data that represent those portions of roads having ranks other than the rank corresponding to the collection but that are accessible within a threshold of the roads of the rank associated with the given collection.