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

[Takenori KANAI]

Markus N and Markus M,

Thankyou for your response.

I see. If on the first step, more surrounding cells have the same
minimum cost, which is the first cell encountered
used (like follows: a is greater than surraounding cells)?
I'm sorry the question on the abc.

2  2  2
2  a  2
2  2  2

Thanks

Takenori K.

> To my knowledge there is no scientific paper available related to the
> r.drain algorithm.
> It has been written by Roger S. Miller in 2001 (replacing an older and
> less functional version).
>
> You may see the internals here in the code base:
> http://trac.osgeo.org/grass/browser/grass/trunk/raster/r.drain
>
> Maybe other users know more about this algorithm family?
>
> Best
> Markus N
> 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
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