[GRASS-user] Obtain r.stream.extract accumulation map?

[Moritz Lennert]

On 14/04/15 23:17, César Augusto Ramírez Franco wrote:
> Hello dear list
>
> I'm using r.stream.extract to obtain a stream network and further
> processing of the vector map (as points using v.to.points) in R to
> generate longitudinal stream profiles and calculate the hypsometric
> curve, but I need to include the accumulation value in my points DB.
>
> The issue I'm having is that if I use r.watershed AFTER v.to.points to
> read the raster values into the points, they don't quite match (i.e.
> points are not where the max accum values are). I assume because I'm not
> calculating the accumulation map the same way r.stream.extract is
> calculating it.
>
> What I want is to obtain the same accumulation map used by
> r.stream.extract when none is specified, how can I do this? It would be
> nice if r.stream.extract would let me save the accumulation map it
> computes for further use.

Are you sure that you calculate the accumulation map with r.watershed 
with the same parameters as r.stream.extract ? The grass7 
r.stream.extract manual says:

"The algorithm is MFD (FD8) after Holmgren 1994, as for r.watershed".

AFAICT this was already true in the grass6 addon.

Another option would be to create the accumulation map before using 
r.stream.extract and feed it to the later as a parameter ('accumulation=').

Moritz