[GRASSLIST:10562] Re: TOPIDX flow direction algorithm

[twiens]

Dylan,

I have a question about r.terraflow.

r.terraflow computes the TCI or topographic convergence
index. AFAIK this is not the same thing as CTI or compound
topographic index or wetness index generated by r.topidx. Am
I mistaken?

T

----- Original Message Follows -----
From: Dylan Beaudette <dylan.beaudette at gmail.com>
To: twiens at interbaun.com
Cc: GRASSLIST at baylor.edu, grass4u at gmail.com
Subject: [GRASSLIST:10558] Re: TOPIDX flow direction
algorithm
Date: Fri, 24 Feb 2006 10:44:30 -0800

> On Friday 24 February 2006 07:31 am, twiens wrote:
> > I'm working with some ArcGIS users and in a note in the
> > AML script to calculate the topographic index, the
> > author notes that ArcInfo uses a D8 algorithm to
> > calculate the contributing area. The concern is that for
> > relatively flat areas, the index value will be
> > inaccurate or inappropriate. I've noted in areas that I
> > have generated a topographic index, that flat areas seem
> to be set to NULL by topidx. >
> > I've not been able to find any reference to this issue
> > in the topidx documentation. Can someone tell me if this
> > concern is valid for r.topidx?
> >
> > Thanks
> >
> > T
> > --
> > Trevor Wiens
> > twiens at interbaun.com
> 
> I would highly recommend enabling c++ support when you
> compile GRASS, so that  you have access to the r.terraflow
>  This will compute a TCI, and in many  cases I have found
> the output from r.terraflow to be superior to the 
> analogous commands in GRASS.
> 
> cheers,
> 
> 
> -- 
> Dylan Beaudette
> Soils and Biogeochemistry Graduate Group
> University of California at Davis
> 530.754.7341
>