4 Replies Latest reply on Aug 8, 2012 12:38 PM by smith984

    Calculate area from raster

      I am having trouble calculating area from a land cover raster layer. I am attempting to select contiguously forested lands 5,000 acres or larger. This layer uses 30m pixels representing 1/4 acre each. I simply do not know how to go about doing this. Any suggestions?

        • Re: Calculate area from raster
          I'm assuming this is a typical landcover layer.  Here are the steps I use:

          1) Make a layer of only forest, using the reclassify tool to make forest classes have a value of "1" and everything else a value of "NoData."

          2) With the forest only layer, use the region group tool to make contiguous forest patches.  The resulting layer will have a value that means nothing (just a group number), but the COUNT field will tell you how many pixels are in each group.

          3) Use the Lookup tool (Spatial Analyst Tool > Reclass) to make a new raster where the value comes from the COUNT field, and multiply this by the appropriate conversion (0.222 for 30 m pixel) to get the number of acres of each patch.

          Hope this helps,

          • Re: Calculate area from raster
            Thank you so much! This was exactly what I needed to know.
            • Re: Calculate area from raster
              This model isn't taking into consideration of topography, right?

              • Re: Calculate area from raster
                I am attempting to use this same approach to map contiguous areas, but the region group tool is creating too many groups--there are areas I would group together that the tool doesn't put together. Is there any way to make it more inclusive? You can only choose a "neighborhood" of 4 or 8 cells.

                Also, when I used the Lookup tool on my raster layer, it produced a strange layer of just lines.