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I'm working on generating a water feature layer that eliminates a lot of the swamp/marsh areas in my county. Using raster analysis (iso unsupervised cluster, majority filter, boundary clean, etc) and converting to a polygon, I now have a layer that more accurately depicts surface water.

However, this also means that I now have a lot of spurious features. Here's a screenshot:

enter image description here

Green is my new layer and blue is the original. Those selected polygons, and all of the other green ones inside the blue boundary, should be 1 feature. However, the attribute table for this selection shows 25 different features. I want these small, isolated singlepart features to be merged together based on the original polygon that surrounds them. It would be like a spatial dissolve where you dissolve based on location instead of attributes. Unfortunately, the closest thing that I could find to my desired process was merging in the editor toolbar, and there's no spatial component to that--it's just selecting by clicking.

It seems like this should be achievable. Any suggestions?

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Occam's razor prevailed and I realized that I could just clip the original layer to the new one.

Consequently, the problem is solved.

  • Other options include intersecting the two layers and then using the blue ID attribute as a dissolve attribute; or select a blue, use select by location to select all green completely within/contained by/whatever method works the blue (making sure to tick the use selected features box) then use Edit > Merge or Dissolve with no attribute specified the resulting green selection. – Chris W Jun 28 '15 at 18:02

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