Remove islands (polygons)

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3
04-04-2012 07:39 AM
yyl
by
New Contributor
Hi all. I have downloaded administrative boundaries from www.gadm.org.
I managed to create a feature layer using[Select Attribute].
Then, I want to remove the small islands and keep only the mainland.
The problem is, i have multipolygon in 1 shapefile, with different fields of same value, no matter where i click on the layer.
Any idea how can i remove the small islands and keep the mainland?

Many thanks.
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3 Replies
MathewCoyle
Frequent Contributor
You can use Eliminate Polygon Part
Or Multipart to Singlepart and delete or definition query out the smaller islands.
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yyl
by
New Contributor
You can use Eliminate Polygon Part
Or Multipart to Singlepart and delete or definition query out the smaller islands.



Many thanks, mzcoyle! The Multipart To Singlepart (Data Management) works!!!:D
I have tried the first one but unavail though.
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MarcBeaudoin
New Contributor
You can use Eliminate Polygon Part
Or Multipart to Singlepart and delete or definition query out the smaller islands.


Yes you can use eliminate or multi to single part but smaller polygons within a land mass with also be removed.  You used to be able to do this quickly in ArcInfo with adjacency something like  reselect smaller than 10sq.km and left or right side poly# equal to ocean or 0 in the case of gadm, syntax is not correct.

How one does this in the ''more sophisticated' ArcGIS I do not know.  Anyone know?
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