[GRASS-user] r.basin Issues Needing Resolution

[Margherita Di Leo]

Hi Rich,

On Sat, Apr 7, 2012 at 12:23 AM, Rich Shepard <rshepard at appl-ecosys.com>wrote:

>  I have several questions about r.basin that I hope can be quickly
> answered.
>
>  1.) Is there an example that can be added to the manual page? I would like
> to better understand the prefix and threshold parameters.
>

r.basin produces several maps for every run, which are flow direction,
accumulation, Horton ordered streams etc.. Prefix parameter is simply a
string given by the user in order to distinguish all the maps produced by a
single run of the program, i.e. every set of coords for outlet. For
example,

r.basin.py map=elevation at PERMANENT prefix=out easting=636654.791181
northing=218824.126649 threshold=20

will produce output maps named:

# raster
out_elevation_accumulation
out_elevation_aspect
out_elevation_dist2out
out_elevation_distance
out_elevation_drainage
out_elevation_hack
out_elevation_hillslope_distance
out_elevation_horton
out_elevation_shreve
out_elevation_slope
out_elevation_strahler

# vector
out_elevation_basin
out_elevation_mainchannel
out_elevation_network
out_elevation_outlet

Threshold parameter is the same of r.watershed. 'Autothreshold ' flag'
simply uses a threshold area of 1 km^2 and is intended as a tentative.


>  2.) There are several module dependencies, but r.stream.basin, r.wf.py,
> and r.ipso.py cannot be downloaded and installed using g.extension;
> they're
> not found in the addon repository.
>

For what concerns r.stream.basin, it is a typo in the documentation,
correct is r.stream.basins, thanks for pointing me out, I just updated it
in the description file.
r.wf.py and r.ipso.py are in the addOns repository:

http://grass.osgeo.org/wiki/GRASS_AddOns#r.wf
http://grass.osgeo.org/wiki/GRASS_AddOns#r.ipso

I can't see any obvious error in the Makefile..... maybe an experienced dev
could please check why they are not working with g.extension.

>
>  3.) The r.stream.extract module is not working for my projects' data using
> version 6.5svn on linux. I have detailed vector maps of the stream networks
> in each of the subbasins I need to describe and model. If I run v.to.rast
> on
> these maps can I use the outlet cell as the values for the easting and
> northing parameters to the command?
>

Please note that r.basin is intended to work with only one outlet at time.
This means you should script it in a for cycle if you run it for several
outlets. You can't give to r.basin the coordinates directly from a vector
map.
I have indicated to run r.stream.extract before r.basin because most of the
times the calculated stream network doesn't match with the natural one, so
that your coordinates should be adjusted to match the calculated stream
network in order to get a result from r.basin. By the way, in a first run
you can give a try with your coordinates.

HTH,
madi

>
> Thanks,
>
> Rich
>
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>



-- 
Ing. Margherita Di Leo, Ph.D.
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