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Thread: Calculate area from raster

  1. #1
    Julie Bellino
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    Question Calculate area from raster

    Hello!
    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?

    Thanks,
    Julie

  2. #2
    Gregory Lipps
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    Default Re: Calculate area from raster

    Julie,
    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,

    Greg

  3. #3
    Julie Bellino
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    Default Re: Calculate area from raster

    Thank you so much! This was exactly what I needed to know.

  4. #4
    Ryan Hollamby
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    Default Re: Calculate area from raster

    This model isn't taking into consideration of topography, right?

    Thanks

  5. #5
    Julia Smith
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    Default 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.

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