How do I "subtract" polygons?

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How do I "subtract" polygons?	Jacob Cuff	Jan 17, 2002
Re: How do I "subtract" polygons?	Kirk Kuykendall	Jan 17, 2002
Re: How do I "subtract" polygons?	Michael Waltuch	Jan 18, 2002
Re: How do I "subtract" polygons?	Lon Sharp	Jan 18, 2002
Re: How do I "subtract" polygons?	Annaliese Vollick	Jan 18, 2002
Re: How do I "subtract" polygons?	David Fann	Mar 06, 2003
Re: How do I "subtract" polygons?	Ray Carnes	Mar 06, 2003

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Subject	How do I "subtract" polygons?
Author	Jacob Cuff
Date	Jan 17, 2002
Message	In ArcView 3.x, if there are two polygons that have boundaries that overlap, you can subtract one polygon from another, buy selecting the two features, and going to the "Edit" pull-down menu and selecting "Subtract Features". Is there a way to do this in ArcView 8.1? I've looked through the help files, arcObjects, etc. and I can't find anything! Please help! Jesse Langdon GIS Analyst Planning Department City of Pflugerville (512) 990-4370 x255 jessel@cityofpflugerville.com

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Subject	Re: How do I "subtract" polygons?
Author	Kirk Kuykendall
Date	Jan 17, 2002
Message	In arcobjects you should be able to use ITopologicalOperator.Difference
	Kirk Kuykendall AmberGIS Programming Services & Sales http://www.ambergis.com Now Answering questions at: http://gis.stackexchange.com/

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Subject	Re: How do I "subtract" polygons?
Author	Michael Waltuch
Date	Jan 18, 2002
Message	If you want to do this from the Editor toolbar, start the Editor (Tools>Editor Toolbar). In the Editor menu select Start Editing. Select the two polygons. In the Editor menu select the operation you want, e.g., Merge or Union. Select Stop Editing. (You can undo operations during the edit session by selecting Edit>Undo ).

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Subject	Re: How do I "subtract" polygons?
Author	Lon Sharp
Date	Jan 18, 2002
Message	That's one of the reasons I've kept 3.2 installed with 8.1

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Subject	Re: How do I "subtract" polygons?
Author	Annaliese Vollick
Date	Jan 18, 2002
Message	It's been a while since I've used 3.2a subtract but believe this works the same or a similar way. 1. Select both polygons (the overlapping and the one to subtract) by drawing a box with the select features tool. Hold shift and click on the outer one to unselect it (the smaller one inside should still be selected). 2. Go to Editor and choose Clip. Should 2 separate polygons with the smaller one subtracted from the larger. It works in SDE polygon layers and shapefiles. I think in 3.2a you need to have both selected -- 8.1 only the smaller one of the 2. Hope this helps. Annaliese

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Subject	Re: How do I "subtract" polygons?
Author	David Fann
Date	Mar 06, 2003
Message	Using "Clip" to subtract polygons works. One major problem, however: The Clip operation acts on the other layers in the map, not just the editing target layer, punching holes in every poly layer simultaneously. Removing the univolved layers, clipping, then bringing them back in protects them, but what a pain! After wrestling with ArcMap for a couple of hours this morning to create three donut holes, I finally gave up and went into AV 3.2. I was done in less than a minute. Sheesh.

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Subject	Re: How do I "subtract" polygons?
Author	Ray Carnes
Date	Mar 06, 2003
Message	David, Did you know that layers that are not visible are not selectable ? If other layers in your document were clipped, it could be because they were selected. If you turn them off before you select your polygon to clip they will not be clipped. This works without needing to remove the layers from ArcMap to protect them from changes. To further control which layers can be selected when visible, under the SELECTION menu, choose the Set Selectable Layers option. Ray.