How to Use Intersections

An Intersection is composed of one or more point locations or a combination of one or more line and point locations. The basic table that describes an Intersection by its Junctions (points) and/or Transportation Elements (lines) is the Intersection Index table (ig). This table builds an Intersection Geometry Index (is), giving a sequence number to all the Elements within the Intersection and defining the Feature Type of these Elements, whether Junctions, Road Elements, Ferry Elements or Address Area Boundary Elements.

A Relation can be made between the Index table (ig) and the Intersection table (is) via the Intersection ID field. The is table contains extra Attributes, Intersection Type and Freeway Intersection Type, for an Intersection. The table also contains the Official Name and Number of the Intersection so that the name of the Intersection can be retrieved for every Element of the Intersection.

The ELEMID field in the ig table is provided to retrieve information about the Transportation Elements in the Network layer (nw) ID field.

Finally, a Center Point represents the central position of a Freeway Intersection by a Point Feature in a separate Center Point of Freeway layer (cf). The Center Point of Freeway is always located on top of one of the Road Elements forming part of the Intersection. This Point Feature gets the same Intersection ID as the Intersection it represents. It is stored in the cf table.