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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