Patent ID: 6118404
Filing Date: 2000-09-12
Classification: G01C

Abstract:
A method of displaying a crossing of at least two linearly extending geographic features that cross at different elevations on a computer display device of a computer based navigation system that uses a geographic database stored on a computer readable medium wherein said geographic database comprises:a plurality of parcels, each containing a plurality of polyline data entities each of which represents a linearly extending geographic feature located within a geographic area;and further contained in each of said plurality of parcels that contains polyline data entities that represent linearly extending geographic features that cross each other at different elevations is a separate overlay data entity that represents each overpass portion of each linearly extending geographic feature that crosses over another linearly extending geographic feature at a higher elevation;the method comprising the steps of:determining a selected portion of the geographic area to display on said computer display device;locating which of the plurality of parcels contains the polyline data entities corresponding to said selected portion of the geographic area;rendering the linearly extending geographic features represented by said polyline data entities contained in said parcel corresponding to said selected portion of the geographic area on said computer display device;rendering the portion of each geographic feature represented by each overlay data entity contained in said parcel corresponding to said selected portion of the geographic area over said rendered geographic features represented by said polyline data entities on said computer display device,whereby the displaying of the overlay data entity over the polyline data entities depicts which of said linearly extending geographic features has the higher elevation where linearly extending geographic features cross each other at different elevations.