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# Extracting Raster Sub Datasets and Converting to Polygon

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12-28-2015 02:30 PM
New Contributor II

Hello all,

I am doing a comparison between two surfaces, the determining how much of that surface has changed within the floodplain I have delineated in this area.   The original was flown in 1998 and the newer one was flown in 2012.  I was able to use the Raster Math tool to determine exactly where and by how much the surface has changed above or below the original elevation.

I was able to manually break the symbology to show what portion of the surface has gone down 2 feet or more from the original, but here I get stuck.  I need a way to extract only that portion of the raster, then convert it to a polygon and quantify area of -2ft. change within the floodplain.

Does anyone have any suggestions?  I am stumped here.  Any help would be greatly appreciated.  Thank you!

Kelly

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1 Solution

Accepted Solutions
Esri Regular Contributor

Dan is 100% right.

However, you could use the CutFill tool to highlight areas of change.

-Steve

3 Replies
MVP Emeritus

All you need to do is query the rasterfor where the value decreased by 2 or more like "diff_raster" <= -2 assuming -2 represents a decrease...  You can then convert that raster to a vector representation

Esri Regular Contributor

Dan is 100% right.

However, you could use the CutFill tool to highlight areas of change.

-Steve

New Contributor II

Thanks, Steve.  I wound up creating another raster dataset and using the CutFill tool.  Worked like a charm.  I should have known that was the answer as I used CutFill to create the floodplains as well. ha!  Thanks again.