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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.