The main accumulation output maps of both r.terraflow and r.watershed are accumulation maps. The value of each cell in these maps is the number of upslope cells contributing runoff to that cell.
Unless you check a flag to turn it off, the values for r.watershed are negative if the contributing basin extends beyond the map or region.
MIchael
______________________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University
Tempe, AZ 85287-2402
USA
voice: 480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax: 480-965-7671(SHESC), 480-727-0709 (CSDC)
www: http://csdc.asu.edu, http://shesc.asu.edu
http://www.public.asu.edu/~cmbarton
On Jul 22, 2011, at 4:14 AM, grass-user-request@lists.osgeo.org wrote:
Date: Thu, 21 Jul 2011 15:35:00 +0200
From: Rainer M Krug <r.m.krug@gmail.com>
Subject: Re: [GRASS-user] flow accumulation
To: frans-joost <fjboogert@gmail.com>
Cc: grass-user@lists.osgeo.org
Message-ID:
<CAGhLh6G7yHDsZquno-1T=iHDX+FKEpMLZugLSJPiMTN+29KOCA@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"On Thu, Jul 21, 2011 at 3:30 PM, frans-joost <fjboogert@gmail.com> wrote:
Dear GRASS users,
I'm trying to implement the Morgan Morgan Finney model for erosion
estimation.
One problem I'm having is with the accumulation of surface runoff.
Is it possible to sum all cells that are uphill, meaning each individual
cell has an amount of water that flows downslope.
It should be possible to use a flow direction map to accomplish this.r.terraflow does not have an option to accumulate using another map
r.watershed gives me very high and negative values (not sure what happened
there)This goes in the direction what I am trying to do with seed dispersal via
water, and I did not get any responses - maybe not possible?Rainer
Thank you in advance
Frans-Joost--
View this message in context:
http://osgeo-org.1803224.n2.nabble.com/flow-accumulation-tp6606761p6606761.html
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