topic reclassify nodata values surrounded by actual values in ArcGIS Spatial Analyst Questions

reclassify nodata values surrounded by actual values

DennisJongsomjit — Wed, 20 Apr 2011 22:25:03 GMT

Hi everyone,

I have a complex raster which has nodata values within it. I want to be able to extract the areas of nodata within it but not the nodata values that surrounds the grid (all around the extent). The simplest example would be a donut. I want to pull out the donut hole (perhaps by converting it to ones) but leave the area outside the donut as nodata.

If I do a simple reclassify of nodata, all the holes and the entire area around the grid gets converted. I don't have a raster mask I could use to pull out these nodata values.

Anyway to do this in spatial analyst???

Thanks,

Dennis

Re: reclassify nodata values surrounded by actual values

DennisJongsomjit — Thu, 21 Apr 2011 16:24:29 GMT

Hi Bill,

Maybe I'm misunderstanding. I did set the analysis environment to use the grid as a mask and then reclassified nodata to 1, but that converts both the holes and the area around the grid.

Is there another environment setting I need to use? I'm doing this in the spatial analyst toolbar and tried setting the mask in both the environment settings and in the spatial analyst option settings.

Or fine to tell me if I'm chasing an impossible dream!

Thanks,

Dennis

Re: reclassify nodata values surrounded by actual values

DennisJongsomjit — Mon, 25 Apr 2011 17:23:06 GMT

RegionGroup! There's a command I had not heard of before but looks like it does exactly what I need.

Perfect, thank you.

-Dennis