topic Re: Extracting Raster Sub Datasets and Converting to Polygon in ArcGIS Spatial Analyst Questions

Extracting Raster Sub Datasets and Converting to Polygon

KellyHanne1 — Mon, 28 Dec 2015 22:30:28 GMT

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

Re: Extracting Raster Sub Datasets and Converting to Polygon

DanPatterson_Retired — Mon, 28 Dec 2015 22:39:59 GMT

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

Re: Extracting Raster Sub Datasets and Converting to Polygon

SteveLynch — Tue, 29 Dec 2015 00:25:37 GMT

Dan is 100% right.

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

-Steve

Re: Extracting Raster Sub Datasets and Converting to Polygon

KellyHanne1 — Wed, 30 Dec 2015 20:26:22 GMT

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.