2D Relationship Tile Connection File

267 © 2016 Open Geospatial Consortium When not specified i.e., blank, the feature is not connected to any other features. Volume 7: CDB Data Model Guidance formerly Appendix A provides guidelines on how to generate the junction identifiers. Since the junction identifier is associated with a shape type feature, the following combinations are supported: ● Any point feature can be connected to any start or end point of a linear feature point to linear connection, or to any start point of a polygon feature point to polygon connection, using its JID attribute. ● Any start point of a linear feature can be connected to any point feature point to lineal connection, or to any start or end point of a linear feature linear to linear connection, or to any start point of a polygon feature linear to polygon connection, using its SJID attribute. ● Any end point of a linear feature can be connected to any point feature point to linear connection, or to any start or end point of a lineal feature linear to linear connection, or to any start point of a polygon feature linear to polygon connection, using its EJID attribute. ● Any start point of a polygon feature can be connected to any point feature point to polygon connection, or to any start or end point of a linear feature linear to polygon connection, using its JID attribute. Connection information between two features located in two separate vector datasets 45 are explicitly listed in 2D relationship files. This standard currently specifies two types of 2D relationship files: the 2D relationship tile connection file which specifies connections of the same dataset feature between two adjacent tiles, and the 2D relationship dataset connection file which specifies connection of 2 or more different dataset and sub-dataset features within the same tile.

5.7.1.6.1 2D Relationship Tile Connection File

Requirement 118 http:www.opengis.netspeccdb1.0coretopo-tile-clip The CDB Topological network is broken into tiles and therefore SHALL be clipped against tile boundaries. To ensure the connectivity between tile boundaries of a lineal feature, the resulting clipping point SHALL share the same junction identifier JID in both tiles 45 Shapefiles if Shapefiles are being used. 268 © 2016 Open Geospatial Consortium This clipping point potentially exists in several Tile-LODs having a common boundary; in which case, all points representing the same clipping point share the same JID. Doing so ensures that connectivity between geocells and tiles is preserved. A clipping point can be identified by the application by checking the 2D relationship tile connection file. There is a 2D relationship tile connection file per network dataset tile. When the file is missing, it indicates there is no clipping point for the lineals belonging to the tile. The 2D relationship file is a dBASE file that contains a list of records made of 2 attributes; the Junction ID JID that identifies the start or end point of the clipped linear and the Network Component Selector 1 NCS1 that identifies the network dataset lineal file. The dataset code file is implicit to the network dataset tile directory and the Network Component Selector 2 always represents a linear feature vector features code 003 thus do not require to be included in the record. The coordinate of the tile adjacent to a clipping point can be determined using the latitude and longitude of that point. If a connection between two linear features happens to be located exactly at a tile boundary, the lineal is obviously not clipped but a junction ID is allocated and included in the 2D relationship tile connection file. In a 2D relationship tile connection file, no two records are identical; however JIDs may appear more than once with different NCS1, indicating a connection between network subdatasets.

5.7.1.6.2 2D Relationship Dataset Connection File