How to delineate/draw the edge of polygon automatically?

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02-07-2017 01:10 PM
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New Contributor III

I would like to delineate the edge of my extraction below, not by hand, just automatically. I want to eliminate the inside polygons and keep the outermost edge only (highlighted by blue, not accurately). Could anyone give me some hints on this part? Thank you in advance!

Edge extraction

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MVP Honored Contributor

Run Dissolve without checking any of the dissolve fields.

If you just want the outline of a few polygons, select them, then run Dissolve.

Dissolve—Data Management toolbox | ArcGIS Desktop 

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New Contributor III

Thanks for the reply. Actually, the above image is what I got from running Dissolve. 

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MVP Honored Contributor

Are those lines or polygons?

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New Contributor III

It's a large polygon with holes inside. Sorry for lack of information.

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MVP Regular Contributor

You'll probably need to manually fill the holes inside or else it's always going to consider those part of the feature when you run Dissolve.

If you wanted to do it semi-manually, you can start editing and trace the boundary you want.

Creating segments by tracing—Help | ArcGIS Desktop 

Also, you posted in the area for help using the GeoNet site. Tagging https://community.esri.com/community/gis/managing-data?sr=search&searchId=c25d959d-9dd7-4320-a287-94...‌ for better visibility.

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New Contributor III

I finally manually edited the shapefile and also ran Eliminate Polygon Part tool. Thank you for the tagging suggestion. 

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MVP Honored Contributor

Ah, you can try Union-ing your existing file with another feature class containing a polygon that covers your entire area, then selecting and deleting the resulting "outside" polygon, and dissolving the "inside" polygons.

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New Contributor III

That's smart! I'll try. I just manually edited the shapefile and ran Eliminate Polygon Part tool. It worked. But your suggestion is so creative. 

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Regular Contributor II

If you have Advanced license.Use Eliminate Polygon Part tool.

Eliminate Polygon Part—Help | ArcGIS Desktop 

and input maximum hole area value in Area ( optional)