How Line Coverage To Region works

This topic applies to ArcInfo only.

The items RINGS_OK and RINGS_NOK are created in the PATsubclass. The values for RINGS_OK indicate the number of closed loops or rings in the preliminary region; the values for RINGS_NOK indicate the number of unclosed rings.

Unclosed rings are included in the preliminary regions and will be used in Build and Clean. In some cases, correct regions may result after structuring; for example, rings that overshoot.

The User-ID in PATsubclass is assigned sequentially, beginning at one, as preliminary regions accumulate in the subclass. The User-ID does not change when you use Build or Clean.

Output Region Item may be the Output Subclass-ID. If this is the case, the value of the Input Region Item overwrites the generated User-ID.

The Line Coverage To Region command structures the arcs into closed rings. The relationship between a region and its boundary arcs is maintained through the region PAL file. The relationship between a region and its polygons is maintained through the RXP (region cross reference) file. Line Coverage To Region constructs the initial region PAL file and creates an empty RXP file. Build or Clean then creates region topology by building the complete RXP file.

After Line Coverage To Region, the RXP is empty. Use Build or Clean to structure the regions.

Structuring preliminary regions with Build or Clean replaces duplicate arcs with single arcs and places nodes where two arcs cross.

Preliminary regions on the left comprise two arcs that partially overlap. The Build or Clean operation replaces the overlapping arcs with a single arc and creates nodes where two arcs cross. The output coverage will contain five arcs.

A one-to-many arc-region relationship is directly maintained through the region PAL file and indirectly through the region-polygon cross reference file.