Struggling to delete very fine sliver-like polygons

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07-21-2020 08:48 AM
tt1
by
New Contributor II

I am currently cleaning up a land classification map by removing slivers. However, I am struggling to manually delete very small sliver-like features as they're connected to a larger polygon which I wish to retain.

Details

I am encountering two types of slivers.


1) Enclosed Slivers, which are their own polygon feature and are surrounded by a larger polygon of a different class.
2) Open Slivers, which are actually connected to a large polygon.

To remove Enclosed Slivers, I select the sliver polygon and delete it to create a gap, fill the gap using auto-complete new polygon tool and then merge it with the surrounding polygon.


To remove an Open Sliver, I use the split tool to create two separate polygons and then repeat the process for Enclosed Sliver (delete sliver polygon to create gap, fill gap using auto-complete new polygon, merge).


However, I have just come across an Open Sliver which is so fine and small that it is not possible to zoom in close enough to split its connection with the larger polygon. See image below

Summary

In the image below, there is a sliver (circled in red) which is actually connected to the large yellow polygon. It is not possible to zoom in close enough to use the "split" tool to split the sliver into its own feature (and therefore delete without removing the large yellow polygon). What can I do to eliminate this type of sliver error?

I am using ArcGIS Pro.

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7 Replies
George_Thompson
Esri Frequent Contributor

When I had stuff like this, I would try to explode out that polygon with the sliver (if possible).

The other option is to create topology and then let the topology engine take care of it.

Topology in ArcGIS—Topologies | Documentation 

I would look at the rule here: Geodatabase topology rules and fixes for polygon features—ArcGIS Pro | Documentation 

--- George T.
tt1
by
New Contributor II

The explode tool seemed to work! Thanks! 

Quick Q. After exploding the sliver into a separate feature, I'll delete that sliver and then fill in the gap before merging it (following the advice here: https://support.esri.com/en/technical-article/000018639 ). 


This seems a bit convoluted. 

A part of me wonders if there is there's a quicker way to remove the sliver and fill the gap?  I have to do this for thousands of slivers so would appreciate anything that is quicker. 

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George_Thompson
Esri Frequent Contributor

For me it is using topology. I did this across counties worth of data for flooding polygons.

The other question would be how did these slices get created? Where did the polygons come from. Based on the screenshot it looks like bad data.

There may be other techniques to remove them based on size, but you may not get them all or remove a valid polygon. If you use topology for this, it will correct both polys at once. So you only delete the sliver and "merge" into the correct polygon.

--- George T.
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tt1
by
New Contributor II

The slices are just due to manmade errors from manual digitising when I'm cleaning up. 

When you say "use topology, it will correct both polys", what exactly do you mean by use topology? 

I have created a topology that contains a single feature class with the rules "should not overlap" and "no gaps". What are the next steps I can take to ensure both polys correct at once?

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George_Thompson
Esri Frequent Contributor

You can merge together the enclosed polys into the one that it should be. That will create a few less steps. Use one of the predefined fixes. You can right click (I think) the error and select a fix that will do both steps together.

Look at the predefined fixes in the help - Geodatabase topology rules and fixes for polygon features—ArcGIS Pro | Documentation 

I thought of another way that may work for the open slivers. Start to edit the polygons vertexes and delete the ones that are part of the sliver. Then use topology to create the new poly and merge with the correct one.

The topology tools should help you correct any errors which will prevent less manual editing.

--- George T.
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tt1
by
New Contributor II

Ah, I see. Unfortunately, these digitisation errors aren't topological errors. The "slices"/"slivers" don't overlap or have gaps, so I believe they wouldn't be detected by topology as an error? 


twowlz
by
New Contributor

I think I'm dealing with a similar issue. It's not a topo error. But I do wonder if there's some way to find and correct these other than clicking on each poly to see if it has a connected sliver. It's not a multipart.

twowlz_0-1644353955588.png

 

twowlz_1-1644354001199.png

 

 

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