Intersection gives a shapefile with duplicate features

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11-21-2013 09:20 PM
DjurdjicaIvkovic
New Contributor
Hello,

I am using the Intersect tool to find which points in one shapefile are located within different polygons in another shapefile. The problem that I have come accross is that a half of the points in the newly created shapefile are duplicated. They are not located on the border of the polygons but within them. I can use Delete Identical to get rid of these duplicates but I want to know why this is happening. If I intersect the same polygon layer and another point layer (with different locations), the shapefile with duplicates is not produced (so, everything seems to be ok). All of the point layers I am dealing with are originating from the excel file containing GPS coordinates which I have exported as a point shapefile.

Thank you.
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3 Replies
JohnSobetzer
Frequent Contributor
The first place to look is for duplicates in the input layer, another is bad geometry and a third is a cranky project necessitating moving everything into a new one before running any tool.  Assuming they are not a problem, then are the points within the tool's, snapping or the layer's tolerance to the polygon edges/vertices?  Of course, there's always just the innate cussedness of ArcMap, and there's no good explanation, just a workaround.  I had that with one layer recently which duplicated one point every time, for no good reason.
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DjurdjicaIvkovic
New Contributor
Hi John,

Thank you for your reply. I tried checking geometry and creating a new project, but it did not help. As to tolerance settings, I did not take that into account. I guess I would have to create topological relationships first, if I am not wrong?
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JohnSobetzer
Frequent Contributor
In the tool itself there is an XY tolerance setting.
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