I've merged together a polygonized raster layer of a certain elevation grade (>25%) and a wetlands buffer. I can't seem to find a good solution to the problem at hand, however. Ultimately I'd like to run a symmetrical difference tool on the merged layer (mentioned in the former) and a parcel layer to find suitable land to build on.

So far I've tried running v.clean (snap, rmdupl, and bpol, all to no avail). Manually cleaning lines is totally out of the question. Dissolving takes a ridiculous amount of time and computing power. Any better alternatives?

Here's what my data looks like:


  • I would suggest doing everything you can to reduce the file size of the red layer. Delete unnecessary attribute fields, try saving it as a different file format, etc. Check out the [file-size] tag for more ideas. Once you have the file size reduced, dissolving won't take as long. – csk Jun 23 '17 at 20:35
  • Do you need to do it with vector analysis tools? The description sounds like raster calculator would be a good fit for the requirements. – underdark Jun 23 '17 at 21:24
  • @underdark how would one utilize the raster calculator for vector cleanup? can you be more specific? – user62160 Jun 23 '17 at 22:11
  • @csk the two vector layers merged together is only 4mB, with about 10k attributes. i'm running it on a MBP with 16gB mem and a dual core. – user62160 Jun 23 '17 at 22:13
  • 10k is a lot of features (assuming you meant features not attributes) for a polygon shapefile. Each component file of a shapefile must be less than 2MB. This has to do with the limits of the shapefile format, not your computer. support.esri.com/technical-article/000010813 – csk Jun 26 '17 at 19:42

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