Empty feature class after erase/intersect/clip

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08-30-2012 12:56 PM
WilliamClark
New Contributor II
I have differentially corrected Trimble collected data on a parking lot.  I want to clip the tree island (red hash) from the actual parking area (light blue).  I have these data in shapefile and in a file geodatabase.  Whenever I run a clip or intersect or erase I get an empty feature class.  There is no errror reported but also no records in the attribute table.  No idea why.  Anyone?

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DanLee
by Esri Regular Contributor
Esri Regular Contributor
You can use Check Geometry tool to see if it flags any invalid geometry for each of the polygon datasets.  If it reports problems, then use Repair Geometry tool to repair them.

Otherwise, if you can share these polygon data, we can have a look.

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DanLee
by Esri Regular Contributor
Esri Regular Contributor
They may not be in the same coordinate system?
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WilliamClark
New Contributor II
They may not be in the same coordinate system?


I wish it was that.  They are both NAD 83 Alaska Albers.  I even converted both to line, edited to the lines I wanted, merged, and try to convert back to polygon.  The conversion back to polygon created an empty feature class.
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
Do this test:

- Run Buffer tool on the parking area polygon with a negative buffer distance (e.g. -2 meters) so that a smaller polygon is created.
- Use the Erase tool to erase the parking area polygonthe by the smaller polygon.

Do you get the parking area polygon with a hole?
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WilliamClark
New Contributor II
Do this test:

- Run Buffer tool on the parking area polygon with a negative buffer distance (e.g. -2 meters) so that a smaller polygon is created.
- Use the Erase tool to erase the parking area polygonthe by the smaller polygon.

Do you get the parking area polygon with a hole?


Yes, this works just fine.
[ATTACH=CONFIG]17396[/ATTACH]
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
Thanks. That means there is nothing wrong with that data. You can try the same with the tree island; if it works fine, then I can't say what could be wrong without looking into the data.  Could you share these data?
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WilliamClark
New Contributor II
Thanks. That means there is nothing wrong with that data. You can try the same with the tree island; if it works fine, then I can't say what could be wrong without looking into the data.  Could you share these data?


It appears the problem is with the tree island.  The buffer (-1m) worked fine.  Erasing produced the following error.  Suggestions on how to proceed?  Thanks, Dan.
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
You can use Check Geometry tool to see if it flags any invalid geometry for each of the polygon datasets.  If it reports problems, then use Repair Geometry tool to repair them.

Otherwise, if you can share these polygon data, we can have a look.
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WilliamClark
New Contributor II
You can use Check Geometry tool to see if it flags any invalid geometry for each of the polygon datasets.  If it reports problems, then use Repair Geometry tool to repair them.

Otherwise, if you can share these polygon data, we can have a look.


Fixed!  Check Geometry reported a self-intersection in the tree island polygon.  Not sure how that occurred (ideas?).  I repaired the geometry, tried the negative buffer test (worked), and then tried erasing from my parking lot polygon - worked again.  Thanks, Dan!
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DanLee
by Esri Regular Contributor
Esri Regular Contributor
You are welcome. I am glad the problem is fixed!

There are more than one possibility how that tree polygon was created with self-intersection. It could be uncareful digitizing; it could be created from another process that didn't write out a valid geometry.  You have to trace back all that, if you really need to find it out so that you can prevent it from happening again in the future.
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