[GRASS-user] What algorithm does r.drain use?

[Will Fields]

You might also take a look at the r.connectivity.* tools:

http://grass.osgeo.org/grass65/manuals/addons/r.connectivity.corridors.html

It looks like it uses the igraph package in R, which has good
documentation.

Regards,

Will

On Thu, Jan 8, 2015 at 6:03 PM, Markus Metz <markus.metz.giswork at gmail.com>
wrote:

> On Wed, Jan 7, 2015 at 7:27 AM, Takenori KANAI <kanai at ube-c.ac.jp> wrote:
> > Hello. I'm sorry by my poor English.
> >
> > I have analyzed distribution of wild animals using r.drain now
> > (http://grass.osgeo.org/grass65/manuals/r.drain.html).
> >
> > Some examples have been described to "EXAMPLES" in an
> > online manual. In "EXAMPLES", there are two ways of cost
> > value though the Cost value of fifith step is 10. In this case,
> > I do not think that there is a problem because there is a
> > smaller cost value since six steps even if the fifth step
> > selects either.
> >  However, by what algorithm has the cell been selected
> > when there are two or more end points in route
> > (There is a minimum same cost value as surroundings of cell. )?
>
> r.drain simply follows the lowest cost in the surrounding cells (must
> be lower than the current cell). If more surrounding cells have the
> same minimum cost, the first cell encountered is used.
>
> Markus M
>
> >
> > Thanks
> >
> >
> > Takenori K.
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