1

I have a layer comprised of about 500,000+ simplified polygons that resulted from converting raster cells to polygons with raster cell values assigned to them. When I select the resultant polygons by attributes (say, those that have values above a certain threshold), I end up with a bunch of contiguous spatial clusters. My goal is to create an outer shell boundary circumscribing those clusters, which can be achieved using the Dissolve Tool in ArcMap.

The problematic twist here is that I want to be able to identify these clusters of dozens of small polygons individually after dissolution into "island" shapes. How would I go about it?

2

your polygon cannot have two geometries. The simple way is therefore to have two layers : one with the dissolved polygons and one with the non dissolved polygons. If you want a single layer that displays like a dissolved one, you can use spatial join in order to extract the ID of the dissolvd polygon for each individual polygon inside it. Then you can display without the polygon boundaries and it will look like dissolved polygon (but each polygon cn still be identified individually).

Final remark: in your case I think that I would rather consider working in raster format and using region grouping to achieve what you want with your dissolve.

  • Thanks for pointing in the right direction. I was able to achieve the end goal by following this sequence of steps: 1) Spatial Analyst -> Conditional > Set Null (specifying the desired attribute value) 2) Conversion tools -> From Raster -> Raster to Polygon 3) Data Management Tools -> Generalization -> Eliminate Polygon Part (with the option of eliminating gaps and slivers within larger polygons, thus achieving a solid shape) Best of all, each such polygon has a unique entry in the layer attribute – user62916 Nov 30 '15 at 19:20
  • thank you for the follow up. Please add this method as an answer to your own question so that others could benefit from it. Comments have a lower visibility. – radouxju Dec 1 '15 at 6:39
0

I was able to achieve the end goal by following this sequence of steps in ArcMap:

1) Spatial Analyst -> Conditional > Set Null (specifying the desired attribute value)

2) Conversion tools -> From Raster -> Raster to Polygon

3) Data Management Tools -> Generalization -> Eliminate Polygon Part (with the option of eliminating gaps and slivers within larger polygons, thus achieving a solid shape)

Best of all, each such polygon has a unique entry in the layer attribute table

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy