topic Re: No attribute table in an aspect raster output - can't use raster calculator in ArcGIS Spatial Analyst Questions

No attribute table in an aspect raster output - can't use raster calculator

MathieuBeaulieu — Tue, 05 Oct 2010 17:57:27 GMT

Hi There,

I used the tool "Aspect" in spatial Analyst > Surface Analysis (standard pull down option)

I successfully created an aspect layer - but I would like to see the distribution of slopes.

I tried the following in raster calculator

([Aspect]*2 + 675 % 720) / 90

as proposed by Mr Huber here: http://forums.esri.com/thread.asp?t=131925&f=40&c=3

but it does'nt recognize my aspect layer. Also, there's no attribute table attached to it.

Any help would be much appreciated

Thanks

Mathieu Beaulieu,
Institute of Resources, Environment, Sustainability
University of British-Columbia
Vancouver, B.C.
Canada

Re: No attribute table in an aspect raster output - can't use raster calculator

KristinaDick — Mon, 27 Dec 2010 20:04:01 GMT

You need to convert the aspect grid to an integer grid before performing any further analysis.

In order to preserve decimal places, first multiply by 10 or 100 etc.

Then use the Spatial Analyst --> Math --> Int tool and finally divide by the same number you multiplied by before.

Hope this helps,

Kristina
Geography Graduate Student
Portland State University

Re: No attribute table in an aspect raster output - can't use raster calculator

MathiasHaarmann — Mon, 25 Mar 2013 20:08:17 GMT

Somehow I´m not able to make head of this. I´d like to extract/select the southern exposition-pixels of an aspect-raster, but these calculations don´t help me: whubers calculation gives out 7 classes of which 6 are actual aspect-classes which are in total 315° (his reference to his older replies in another thread doesn´t work for me). And Kristina´s calculations results in a raster, with a range of values between -1 and 359, which is somewhat crude not including 360. Maybe we can "reheat" the topic for ArcGIS 10.1 again?

Regards and thanks in advance,
Mathias

Re: No attribute table in an aspect raster output - can't use raster calculator

MathiasHaarmann — Sat, 30 Mar 2013 13:45:41 GMT

somewhat I don´t see the edit button anymore, strange...

Anyway: I did it with TINs