[GRASS-user] flowdirection

[Manuel Seeger]

Hello Maciej,

thank you for the information. I dindn't find the description you gave within 
the manual of terraflow.
Another thing:
within my test area, it produces absolutely the same flowdirection running as 
MFD of as SFD. Is this a bug? Or where is the problem?
Did someone else test it?

Manuel

Am Mittwoch, 6. Dezember 2006 22:17 schrieben Sie:
> Hamish wrote:
> > Manuel Seeger wrote:
> >> another thing. when I use Terraflow with MFD, how are the
> >> flowdirections expressed in the flowdirection grid? I get values
> >> between -1 and 255, but I'm  not really shure how to treat them/ what
> >> they express.
> >
> > M.D.F.= multi-dimensional flow
> >
> > MDF directions:
> >  (based upon the rules in r.terraflow's findDominant() funtion in
> > direction.cc)
> >
> >    32 64 128
> >    16 *   1
> >    8  4   2
> >
> > so a value of 255 is flow in all directions, a value of 3 is E and SE, a
> > value of 65 is E and N, etc. I'm not sure exactly what 0 and -1
> > represent, hopefully that becomes obvious.
> >
> > The r.terraflow help page talks about MDF a bit, it should really have
> > this info too.
>
> Working on it. There was quite a bit to cleanup in the r.terraflow's
> description.html anyway.
>
> Could someone please say what 0 and -1 represent, which Hamish asks, so
> I include this in the manual? Is null possible?
>
> And how is the flow direction coded in case of SFD? Same as MFD, only
> no multiple directions, thus only 1,2,4,8,16,32,64,128 direction is
> possible? (that's what I assume...).
>
> Please find the attached description.html + pngs and comment them.
>
> Maciek

-- 
Dr. Manuel Seeger
Wiss. Assistent						Scientific Assistant
Physische Geographie					Dpt. of Physical Geography
FB VI - Geographie/Geowissenschaften		Geography/Geosciences
Universität Trier						University of Trier
D - 54286 Trier
Tel.:		+49-651-201 4557
Fax:		+49-651-201 3976
Web:	http://www.uni-trier.de/uni/fb6/geographie/mitarbeiter/Seeger/