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I’ve got a series of square overlapping polygons. I want to clip a layer based on these polygons and maintain the unique ID and overlap of the polys. As it is now, if I do a clip using overlapping polygons, the clip will automatically merge all the unique polygons (see attached) by basically assuming the square polygons are one big mask. You can see that many of the square polygons overlap significantly and will have nearly identical clip results-which is exactly what I want. Aside from clipping one polygon at a time (there are 3,000+ of them), I cannot figure out a solution. There don’t seem to be any options to tell ArcGIS to turn off the automatic merge.

Example

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    Did you try Union and then Dissolve on the Unique ID from each original polygon? The overlaps will split the polygons more than you want, but if you dissolve the result you should end up with the duplication you want to occur in the overlapping areas. You should exclude from the dissolve all portions where the blue polygon FID equals -1.
    – Richard Fairhurst
    Commented Apr 30, 2015 at 22:40
  • What do you mean 'maintain unique id'? You cannot keep OBJECTID/FID values - they are controlled by the system that they'e stored in. If you want to keep these values then create a field (long) and field calculate the OBJECTID/FID into it, now that the values are in a static field they wont change during clip/union/intersect. I'd go with the previous comment by @RichardFairhurst, then dissolve by any important attributes - when you dissolve only the dissolve attributes will exist in the output, so if it's important it must be a dissolve field.
    – Michael Stimson
    Commented Apr 30, 2015 at 23:39
  • Are you wanting to duplicate the blue polygons for each square? Because that's not really just a clip. It's more like a Split, except I don't know that would work with overlapping split features or not. And while I see what Richard is getting at, if you want what I think you do then I don't see how you'd do it without an iterative model running clip for each square and ending up with a lot of stacked polygons.
    – Chris W
    Commented May 1, 2015 at 0:15

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Use Intersect and then Dissolve. See the result below of my use of these two tools. It duplicates the blue polygon for all overlapping square polygons and preserves the FIDs of both layers in new fields. A dissolve that includes both FID fields ends up with each original square's intersection with each blue polygon it touched. It works.enter image description here

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  • Ah-ha! I was wondering about Intersect vs Union in your comment earlier, and thinking Union wouldn't work because there would be no overlap/duplication like there would with Intersect, so you'd have to use multiple dissolves to generate the desired result.
    – Chris W
    Commented May 1, 2015 at 6:38
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    Chris W - Actually Union will work exactly the same way for the overlapping portions, but it includes areas that are not needed. Both tools will duplicate all overlapping portions the same way, and the Intersect portion of the Union output can be isolated with a query. In my example the Union Output query equal to an Intersect output is FID_FLOOD > -1 AND FID_SQUARES > -1. But the Union tool also includes all non-overlapping areas, which are not necessary in this case. I tend to use Union, because often I do need to include the non-overlapping areas for comparisons to the original areas.
    – Richard Fairhurst
    Commented May 1, 2015 at 15:49
  • You're right - I was either misremembering or had just completely forgotten what happens in a union where there are overlapping features within one of the inputs. For some reason I was thinking each piece of overlap became a separate polygon with the id/attributes of the originals, period, but as you say anything in the same fc is actually duplicated (or rather just cut up - not really duplicated since it's all there to start with) so then anything with a match in a different fc would have two polys to union to.
    – Chris W
    Commented May 1, 2015 at 20:18

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