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Deleting overlapping polygons in a Theme   James Mitchell Nov 19, 2005
Re: Deleting overlapping polygons in a Them...   Dan Patterson Nov 19, 2005
Re: Deleting overlapping polygons in a Them...   Tift Tax GIS Nov 23, 2005
Re: Deleting overlapping polygons in a Them...   Chris Nelson Nov 22, 2005
Re: Deleting overlapping polygons in a Them...   Jessica Ross Apr 21, 2008
Re: Deleting overlapping polygons in a Them...   Tift Tax GIS Apr 21, 2008
Re: Deleting overlapping polygons in a Them...   Ronnie Richards Sep 23, 2009
Re: Deleting overlapping polygons in a Them...   Helen Enander Oct 21, 2009
Re: Deleting overlapping polygons in a Them...   Thomas Roussell Nov 18, 2009
Re: Deleting overlapping polygons in a Them...   Ronnie Richards Dec 15, 2009
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Subject Deleting overlapping polygons in a Theme 
Author James Mitchell 
Date Nov 19, 2005 
Message Hello,

I have a shapefile that has been merged with another shapefiel so there are some areas with two polygons one on top of the other.

I was wondering how i can detect all the polygons that are overlapping and then delete them?

The only way i have found so far is to use ET GeoTools to detect the overlaps and then remove them individually, or delete the overlaps manually when i find them.

Therefore is there anyway of detecvting all overlapping polygons and then delete them?

My license type is Arcview.

Thank you for any help 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Dan Patterson 
Date Nov 19, 2005 
Message doing it interactively allows you the safety net of deciding which attributes to keep if the attributes differ but the geometry is the same 
  Geomatics, Carleton University, Ottawa, Canada 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Tift Tax GIS 
Date Nov 23, 2005 
Message Dan - on a related ArcEditor 9.1 issue - we have a zoning shapefile which is "dirty", polys stacked on polys, overlapping different ones underneath, as if somebody laid small rugs on top of wall-to-wall carpeting.
If I convert the shapefile to a pgdb, is there any way, either in the conversion or later, to "squash" the polys down into one layer, preserving the boundaries of the successively smaller polys? 
  dirty_shapefile.GIF (opens in new window)
 
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Subject Re: Deleting overlapping polygons in a Theme 
Author Chris Nelson 
Date Nov 22, 2005 
Message Hopefully this will help....

There is a way to select all of the polygons in one layer that overlap polygons in another layer. "Selection -> Select By Location" will allow you to do so.

Two catches:

You'd have to either revert back to the two polygon layers before you merged them - unelss you figure out how to use the same layer twice; it may be possible.

Also, I'm not too familiar with what ArcView does and doesn't have compared to ArcInfo, so I'm not sure if you have that option.

Sorry I couldn't be of any more help! 
  Chris Nelson
GIS Analyst, DPW
Bedford, MA 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Jessica Ross 
Date Apr 21, 2008 
Message Was there ever a solution for this issue? Is there a tool I can use in 9.2 with sp5? Will "repair" fix or find the overlap?
In an overlap situation I need to keep one polygon there...just not two.
Thanks so much,
Jessica 
  Jessica Ross
GIS Specialist
GreenForest Management Inc.
Thunder Bay, ON 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Tift Tax GIS 
Date Apr 21, 2008 
Message As I remember the process in ArcEditor 9.1 from 3 years ago - I took the poly shapefile and converted it to a geodatabase feature with topology. Set the topology rules to "must not overlap" and "must not have gaps". The topology will then show overlaps or gaps and you can deal with them with full control over what you discard.

As for tools in 9.2, somebody else will have to tackle that, sorry. 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Ronnie Richards 
Date Sep 23, 2009 
Message Not sure if this is the original poster's desired solution but is probably easier than most of the recommendations.

Perform an Intersect with your polygon feature class with it being the only input. The output feature class will include only polygons that overlap (and also split's them). Now at least there is a visual reference to investigate the issues. If your poly layer has a keyID field you can perform frequency's and joins to see how problematic the issues might be.

Topology is great... I just wish there were reports available for the affected features. 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Helen Enander 
Date Oct 21, 2009 
Message I convert the shapefile to the old coverage data type - it doesn't allow overlaps or gaps - and then convert it back to a shapefile. This works well for filling in gaps. One can then dissolve features below an appropriate areal size to "absorb" the filled in gaps into adjacent polygons. For overlaps, the overlapping area(s) all become a separate feature(s). 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Thomas Roussell 
Date Nov 18, 2009 
Message I have a similar problem. Nightly, I have a process that downloads a shapefile from our government. The shapefile has over 4000 overlapping polygons. Each polygon is identified with an ID number. When there are overlapping polygons, I need to keep the polygon with the highest ID number (there may be several). I also need to keep all the polygons that have no overlaps. Obviously I cannot do this manually. Is there any way to automate this? 
   
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Subject Re: Deleting overlapping polygons in a Theme 
Author Ronnie Richards 
Date Dec 15, 2009 
Message Not knowing all of your requirements or datatypes... this could probably be done in a few overlay steps with model builder and python.

-Perform an Intersect to find the Overlap Areas
-Convert these overlap geometeries to points
-Overlay points with original polys
-Summary
-If poly has more than 1 point then choose max(id)
-Join and create final output file

-Identities, Joins, Summaries and a Search Cursor would be the tools to support the operations mentioned above.