[GRASS-dev] r.watershed question

[Michael Barton]

Thanks much. I swear I looked at the help file but somehow did not see  
this.

I appreciate your help.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

Phone: 480-965-6262
Fax: 480-965-7671
www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu







On Sep 17, 2009, at 12:14 PM, Jarek Jasiewicz wrote:

> negative numbers are assigned to cells which contribute outside area
> numbers refers to direction:
>
> 3 | 2 | 1
> --- --- ---
> 4 | 0 | 8
> --- --- ---
> 5 | 6 | 7
>
> you can find direction by multipy the number by 45 (against east CCW)
>
> from help page:
>
> /drainage/
>    Output map: drainage direction. Provides the "aspect" for each cell
>    measured CCW from East. Multiplying positive values by 45 will give
>    the direction in degrees that the surface runoff will travel from
>    that cell. The value 0 (zero) indicates that the cell is a
>    depression area (defined by the depression input map). Negative
>    values indicate that surface runoff is leaving the boundaries of  
> the
>    current geographic region. The absolute value of these negative
>    cells indicates the direction of flow.
>
> Jarek
>
> Michael Barton pisze:
>> r.watershed can produce a map of "drainage directions".
>>
>> The values of a direction map are in the range of -8 - +8
>>
>> Can someone tell me what these numbers refer to? That is, what
>> direction is 3 or -3? I've tried to run some correlations against an
>> aspect map and am not getting meaningful results yet.
>>
>> Thanks
>> Michael
>>
>>
>> ____________________
>> C. Michael Barton
>> Director, Center for Social Dynamics & Complexity
>> Professor of Anthropology, School of Human Evolution & Social Change
>> Arizona State University
>>
>> Phone: 480-965-6262
>> Fax: 480-965-7671
>> www: www.public.asu.edu/~cmbarton, http://csdc.asu.edu
>>
>>
>>
>>
>>
>>
>>
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