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I have a large shapefile that I'm working with in ArcGIS 10.5 with an ArcInfo license.

At any given location in the file there are multiple polygons.

In the example I am working on there is a particular value; overlapping animal ranges.

There is a value associated with each of these ranges (polygons), and I'd like simply represent the largest value of several overlapping polygons (I might also want to show the high, low or some other statistics). So any given area will be represented by a single polygon, and a single area.

I was able to dissolve and 'split' the overlapping .shp file into it's constituent parts and I tried 'unioning' them back together with the largest value as the highest priority.

I also tried 'merge' with no luck. This seems like it should be simple, but I keep running into a brick wall.

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  • In QGIS you could style the layer to give colour attributes to the ranges that you want to display and then you could just turn styles on and off as needed. It sounds like you are overcomplicating it by trying to merge and union polygons.
    – Martin Hügi
    Oct 22, 2017 at 19:29
  • That's a good point, but for the purposes of converting these overlapping polygons to a simple .kml and webmap, I can't have any overlapping polygons.
    – Jim Richalds
    Oct 23, 2017 at 14:18

1 Answer 1

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In Arcmap you would achieve this in 6 steps which can be easily strung together as a model.

You basically Union the layer itself, extract out the centroid XY's, create an ID based upon the centroid XY (a string field concatenating the X and the Y) and it is that that allows you to generate aggregated statistics for the overlapping regions.

Initial sample data

Sample data - overlapping polygons labelled with value

The model

The model

Done

The data with summary table joined backed to Union dataset using the common XY string field and symbolised by MAX value

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  • Is there a way to do this that results in with zero overlapping polygons, and only the MAX value of any given area represented by a single polygon. The most important thing is to remove overlapping polygons. A given area that was previously represented by multiple polygons will now have only show the polygon of highest value.
    – Jim Richalds
    Oct 23, 2017 at 14:21
  • ehh... Yes, Exactly what I just said in the answer above...
    – Hornbydd
    Oct 23, 2017 at 14:51
  • Ok, I might not be understanding what you did. It looks like e.g. the #11 polygon underlies the #30 polygon. So it's just symbolizing the Max value, which is nice, but there are still polygons underlying.
    – Jim Richalds
    Oct 23, 2017 at 16:15
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    Two steps are missing in above solution: delete identical from union and joining summary table back to what remains. But it is a legit solution.
    – FelixIP
    Oct 23, 2017 at 18:45
  • @FelixIP is correct, not sure why I did not include the delete identical tool in the model, probably because it's an Advance level tool but there others ways to identify duplicates and remove them.
    – Hornbydd
    Oct 23, 2017 at 21:26

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