[GRASSLIST:1867] Re: basin area

[Eric G. Miller]

On Wed, May 23, 2001 at 03:59:59PM -0600, Roger S. Miller wrote:
> 
> On Wed, 23 May 2001, Daniel Amorese wrote:
> 
> > Hello,
> >
> > Please, can you tell me how  (what are the different steps ?) to
> > compute the area of each drainage basin output by r.watershed ?
> > Any assistance is much appreciated.
> 
> Use the r.stats command with the -a flag set.  The cells within each basin
> defined by r.watershed are assigned the same category value.  The command
> prints a list of raster categories and the area (in square meters)
> represented with that category.  In the case of r.watershed basins, those
> areas are the watershed areas.
> 
> r.stats will also calculate a number of other values if you ask it to.

Also, if you want an estimate of surface area (vs. planar) you might
look at r.surf.area.  It'll need the original elevation model, but you
can mask for each basin output and run iteratively.  It gives high/low
estimates as well as the planar values.  There's a little bit of error
on the edges since 3 cells are needed for triangulation.  It's also
region resolution sensitive.

-- 
Eric G. Miller <egm2 at jps.net>