[GRASS-user] multiflow direction models

[Dylan Beaudette]

Thanks for the description Helena.

All this talk about Tarboton, reminded me of a paper on his website that goes 
into a bit of the background on other problematic terminology. In addition, 
there is an interesting overview of stream network extraction via detection 
of curvatures in a DEM:

http://www.engineering.usu.edu/dtarb/asce2001.pdf

Cheers,

Dylan

On Monday 15 May 2006 14:41, Helena Mitasova wrote:
> Jus a short explanation - people often mix 2 things - flow direction
> and flow accumulation.
>
> You can have the following flow/gradient direction:
> D-4 (direction is discretized with 90 deg step), D-8 (discretized
> with 45 degree step), D-inf (discretization is
> defined by FP precision)
>
> The flow accumulation can be computed as
> SFD (single flow direction - all water flow into single lowest cell),
> MFD (multiple flow direction - water is distributed into multiple
> lower cells - different rules can be set),
>   full 2D (bivariate routing according to continuity equation).
>
> You can combine these in different ways, none of the methods in GRASS
> is exactly the same as Tarboton's.
>
> Helena
>
> On May 15, 2006, at 5:15 PM, Dylan Beaudette wrote:
> > Kessie,
> >
> > Ah. Well this might be a good time to ask the GRASS developers to
> > clarify. You
> > might also check out the docs behind r.terraflow .
> >
> > cheers,
> >
> > Dylan
> >
> > On Monday 15 May 2006 13:51, Ksenia Konwicki wrote:
> >> Thanks Dylan.
> >>
> >> I followed this string fairly closely when it was active. I have
> >> investigated r.flow and r.flowmd.
> >>
> >> Question though... I am a little confused by the r.flow
> >> documentation. It
> >> states that it used the D-inf logarithm to calculate flow direction,
> >> however flow accumulation uses a single flow direction logarithm. The
> >> r.flowmd module appears also offer D-inf flow direction however it
> >> seems to
> >> only offer the Desmet & Govers multiflow contributing area
> >> calculations for
> >> flow
> >> accumulation.
> >>
> >> Our research favours Tarboton's algorithms. We would like to use
> >> GRASS for
> >> the computations however we will have to find a programmer or
> >> another Open
> >> Source option if it is not available.
> >>
> >> Thank you,
> >>
> >> Kessie.
> >>
> >> Dylan Beaudette wrote:
> >>> Kessie,
> >>>
> >>> Might check on some past GRASS-user messages on this thread:
> >>>
> >>> http://grass.itc.it/pipermail/grassuser/2006-February/032744.html
> >>>
> >>> Perhaps it would be a good time to create a page on this...
> >>>
> >>> Dylan
> >>>
> >>> On Monday 15 May 2006 11:34, Ksenia Konwicki wrote:
> >>>> Good morning,
> >>>>
> >>>> I am wondering if anyone knows whether David Tarboton's D-infinity
> >>>> multiflow direction algorithms have been integrated into a GRASS
> >>>> module.
> >>>>
> >>>> Thank you,
> >>>>
> >>>> Kessie.
> >>>>
> >>>> --
> >>>> Ksenia E. Konwicki, RPF
> >>>> Ecologist
> >>>>
> >>>> Timberline Forest Inventory Consultants
> >>>> 1579 9th Avenue
> >>>> Prince George, BC   V2L 3R8
> >>>> P (250)562-2628
> >>>> F (250)562-6942
> >>>> E kes at timberline.ca
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> grassuser mailing list
> >>>> grassuser at grass.itc.it
> >>>> http://grass.itc.it/mailman/listinfo/grassuser
> >>>
> >>> --
> >>> Dylan Beaudette
> >>> Soils and Biogeochemistry Graduate Group
> >>> University of California at Davis
> >>> 530.754.7341
> >>
> >> --
> >> Ksenia E. Konwicki, RPF
> >> Ecologist
> >>
> >> Timberline Forest Inventory Consultants
> >> 1579 9th Avenue
> >> Prince George, BC   V2L 3R8
> >> P (250)562-2628
> >> F (250)562-6942
> >> E kes at timberline.ca
> >
> > --
> > Dylan Beaudette
> > Soils and Biogeochemistry Graduate Group
> > University of California at Davis
> > 530.754.7341

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341