topic Re: Raster Calculator problem. in ArcGIS Spatial Analyst Questions

Raster Calculator problem.

ChristopherBlinn — Thu, 17 Feb 2011 01:00:17 GMT

Hello,

I think I may be trying to do something out of my GIS capabilities...

I want to use the raster calculator to create a "relative elevation" DEM. Currently I have a DEM of an entire state. The DEM has a 10 meter resolution. I want the raster calculator to read the input cell value, and then apply a buffer and search the values of the cells within that buffer (say 1000 meters from the input cell) and take the average of those cell values. Then I want the output DEM to be made of the average values. Also, I want the new DEM to have a resolution of 1000 meter resolution.

Am I dreaming too big here? If possible, I am pretty sure it will involve some Python scripting. I am working with ArcGIS 10.0 if that helps in any. Any feedback is helpful and thank you in advance!

Re: Raster Calculator problem.

DanPatterson_Retired — Thu, 17 Feb 2011 10:28:26 GMT

did you rule out Aggregate?
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z00000034000000.htm

Re: Raster Calculator problem.

PatrickTaurman — Thu, 17 Feb 2011 11:32:37 GMT

Have you thought about using Majority Filter?

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z00000037000000.htm

Re: Raster Calculator problem.

ChristopherBlinn — Fri, 18 Feb 2011 14:35:03 GMT

Thank you all for your replies. Let me work with these grid tools and post back any updates.

Re: Raster Calculator problem.

ChristopherBlinn — Mon, 21 Feb 2011 19:35:01 GMT

Ran the focalstatistics, and the output raster was a solid black rectangle. Bad right? Well, although it was all black, each cell was calculated correctly and has a significant value. The symbology of the raster however is all screwed up. Any ideas why?

Re: Raster Calculator problem.

ChristopherBlinn — Fri, 25 Feb 2011 00:09:26 GMT

Any way to identify these outliers? Then run a con statement to make sure when the script runs these cells do not have extreme values? Just ideas at this point.

Re: Raster Calculator problem.

ChristopherBlinn — Sun, 27 Feb 2011 20:47:40 GMT

Okay, so here's the situation.

My original raster has a range of values from 180.8 to 4132.9. The output raster after running the focal statistics has a range of values from 256 to 3969.2. The focal statistics script I ran was:

FocalStatistics("RASTERNAME",NbrCircle(1500,"MAP"),"MEAN")

There appears to be no outliers in my data. Now, could NoData cell values be causing this error? If so can I run the following to correct for the problem?

FocalStatistics(Con("RASTERNAME","RASTERNAME","",FocalStatistics("RASTERNAME",NbrCircle(100,"MAP"),"MEAN")),NbrCircle(1500,"MAP"),"MEAN")

I think this script would fill the NoData values with an average value calculated by the neighborhood created. Maybe I am wrong.

I am sorry if I am not making too much sense, I am very new to working with rasters, much of my experience is in vector-based GIS work.

Re: Raster Calculator problem.

ChristopherBlinn — Sun, 27 Feb 2011 20:49:32 GMT

Attempted running that script, received two errors, 539 and 999999.

Guess I need to try something else.

Re: Raster Calculator problem.

ChristopherBlinn — Sun, 27 Feb 2011 21:03:26 GMT

Did you know that the "-" symbol can cause a bunch of problems because of syntax rules? Me either, until about 5 minutes ago.