topic Re: Divide tool results in one value in ArcGIS Spatial Analyst Questions

Divide tool results in one value

CaitlanReilly — Thu, 26 Aug 2010 17:21:48 GMT

Hello all,
I have a few rasters that I have been trying to divide by 1000 in order to obtain a useful number for each pixel. However when I run the tool, I get a raster with a single value for every pixel and an attribute table with one entry. I get the same result when I use the raster calculator and also the divide tool in ArcToolbox. Other functions seem to work OK for the same raster (like multiply), so not sure what the problem is. Any help would be greatly appreciated!

Thanks,
Caitlan

Re: Divide tool results in one value

DanPatterson_Retired — Thu, 26 Aug 2010 17:49:25 GMT

Read the help carefully
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//005m000000ms000000.htm
but I suspect that you have an integer grid and divided by an integer (aka 1000) which results in an undesireable outcome. So try to divide by a float (aka 1000.0 ) which should result in a floating point grid which will lack a table and may not be what you want afterall

Re: Divide tool results in one value

CaitlanReilly — Thu, 26 Aug 2010 18:17:53 GMT

Well I have gotten around the problem by multiplying by 0.001, but I was interested in seeing if using a floating point (1000.0) would work so I tried it anyway. I still got the same result- one value for the whole raster. I'm thinking that there is some sort of issue with my raster. I tried to export it as a grid (it says it is an IMAGINE image), but that failed to execute.

Re: Divide tool results in one value

CaitlanReilly — Thu, 26 Aug 2010 18:31:11 GMT

I think I have figured out what may be causing the problem. My raster is a 16bit unsigned integer raster. When I divide by 1000, it gives me a single value because it is integer/integer.

Re: Divide tool results in one value

DanPatterson_Retired — Thu, 26 Aug 2010 18:32:28 GMT

right-click on the layer, select Data | Export Data, towards the bottom right, where it says Format, did you select Grid? Then don't give it an extension but ensure that the Name is less than 13 characters, doesn't contain spaces and doesn't begin with a number...also navigate to a folder that doesn't contain spaces either, so it you "stuff" is going to C:documents and settings...that is a big no no. See if the divide by 1000.0 works on a grid, which I assumed you had been working with.

Re: Divide tool results in one value

CaitlanReilly — Thu, 26 Aug 2010 19:10:08 GMT

I tried exporting it as a grid before and it doesn't work for some reason- I get a failed to execute error. It says that it is an IMAGINE image, but I don't see why that would stop me from being able to export it to a grid.

Re: Divide tool results in one value

YafitCohen — Thu, 04 Aug 2011 04:51:37 GMT

Hi,
I have similar problem. I have used a 12-bit GRID with the raster calculator in this way
Float((raster-1000)/10)
I got a raster with no table which is very annoying but the worse problem is that I get only numbers of 20.000, 30.000, 31.000 etc - which means I cannot see numbers like 31.5 and 20.8.
Can you please let me know what do I do wrong? Or what should I do in order to get these kinds of numbers.

Thank you very much,
Yafit