topic Raster to polygon problems in ArcGIS Spatial Analyst Questions

Raster to polygon problems

grahamlangley-edwards — Wed, 25 Apr 2012 19:23:18 GMT

Hi, I am trying to convert a raster to polygon in ArcGIS 10. I initially used the Extract by Attributes tool to isolate elevation ranges between 1900 and 3800 meters from a 90m DEM. I want to convert that into a polygon that I can use to clip an area of interest from some satellite tiles. When I convert from Raster to Polygon I get a grid instead of a polygon (Screenshot2). I also included an up close shot of the grid (Screenshot). I'm not sure why this is happening. The only options I have are to change the field parameter from Value to Count, but that also returns a grid structure. How can I create a regular polygon from this data? Any help is greatly appreciated....

Thanks,

Graham

Re: Raster to polygon problems

Anonymous User — Wed, 25 Apr 2012 19:47:25 GMT

Original User: dkwiens

Either:
1.) reclassify your raster so that all of the values between 1900 and 3800 have the same value, then convert the cells with that value to a polygon.
or...
2.) make a dummy column in the polygons you have now, make it equal the same value for all polygons, then Dissolve them all into one big polygon based on that column

Re: Raster to polygon problems

grahamlangley-edwards — Wed, 25 Apr 2012 21:38:13 GMT

Darren,

Thanks for your reply! I chose option 2, as it seemed a little more straightforward, and it worked perfectly. I appreciate your time.

Thanks again,

Graham

Re: Raster to polygon problems

Anonymous User — Fri, 27 Apr 2012 14:25:13 GMT

Original User: curtvprice

I want to convert that into a polygon that I can use to clip an area of interest from some satellite tiles.

Seems to me a more direct approach would to create a mask using the Set Null tool - and then use Extract By Mask. (No need to create polygons that way.)

As they say, raster is faster, but vector is correcter.