Decompose

Applicability:

• Cadcorp SIS Map Modeller
• Cadcorp SIS Map Editor
• Cadcorp SIS Map Manager
• Cadcorp SIS ActiveX Modeller
• Cadcorp SIS ActiveX Manager

Ribbon Group:

Create-Edit

Conditions for use:

• Item Class: All item classes
• Number selected: 1
• Minimum item status: Editable

Associated commands:

• Add Geometry
• Convex Hull
• Fill
• Process
• Remove Geometry
• Unfill

Description:

 Decompose breaks down the selected item with complex geometry, so the disconnected pieces form separate items.

Note: Any attribute data stored with the complex item will be lost.

Example - Using Decompose to edit a MultiPolygon:

 Decompose converts the MultiPolygon back into its component Polygons.

Alternatively you can use Remove to remove a single Polygon from a MultiPolygon. In this case select the MultiPolygon, select Remove and click on the Polygon to remove.

Where you have a MultiPolygon which was created from overlapping Polygon items, the overlap would have been converted into a hole. If you later decompose a MultiPolygon with a hole, you do not get the original Polygon items back. Instead, you get these Polygon items minus the hole:

Example - Decompose and attribute data

 Decompose appends any attributes on the original item to all of the decomposed items.

You may find it easier to edit the existing attributes in what are likely to be common item types than to input them again from scratch.

1. Select the complex geometry in the map window that you want to decompose:
   
   
2. Select Decompose
   
   
3. The complex geometry becomes separate items.

In this example, the complex geometry would decompose into two closed LineString items. Both retain the same attributes, but, as you might expect, the geometry properties in the two LineString items will be different.

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