Measure average within overlapping buffers

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09-14-2017 10:32 AM
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New Contributor

Hello,

I need to measure average income within buffers that I traced around polluting plants. The income data comes from a polygon file with census-tract level income. I have tried to use the intersect tool (the plan was to use the statistics tool after, once I had linked each buffer to all the intersecting census-tract), but it does not work. I think the problem is that the buffers can overlap with each other. Is there any solution that you could suggest? Thanks!

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MVP Honored Contributor

What software package are you using to do this? Please add some more description to your text and use additional tags. Also, instead of posting to GeoNet Help‌, which is for questions about Geonet itself, move this to a more suitable place.

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MVP Honored Contributor

I feel like intersect should get you most of the way there, if I'm picturing this correctly. If your buffers overlap, intersect will create multiple overlapping intersection polygons tied to their respective pollution source, which should be fine, although I don't know how you want to consider areas that are polluted twice or more.

 I think you will eventually have to calculate the area percent of each buffer size, so you can multiply that by the average income (e.g. 90% high income + 10% low income should be weighted toward high income).

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New Contributor

Thanks for your answer. Using intersect and then taking a weighted average (by area) is what I had in mind. However, when I try to intersect the buffers with the census data shapefiles after a few minutes I get an error message, and I think this is because of the self-overlapping polygons. I find it hard to figure what is wrong otherwise

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MVP Honored Contributor

I have definitely used intersect with self-overlaps in the past. What is the error message?

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New Contributor

It says "output feature class empty" (see screenshot).Do you know where I can find a more detailed description of the error? 

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MVP Honored Contributor

Since it mentions invalid topology, try running Check Geometry and/or Repair Geometry to fix the topology.

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