[GRASS-user] r.watershed: Problems Using

[Rich Shepard]

On Wed, 10 Feb 2010, Markus Metz wrote:

> The segment library failed to format a temporary file, it could not write
> to the file, but I don't know why. What does g.region -p say,
Markus,

GRASS 6.4.0svn (Oregon):/usr4/grassbase > g.region rast=aber5m res=5 -ap
projection: 99 (Lambert Conformal Conic)
zone:       0
datum:      nad83
ellipsoid:  grs80
north:      1334420
south:      1279150
west:       769190
east:       819260
nsres:      5
ewres:      5
rows:       11054
cols:       10014
cells:      110694756

   That's 110 million cells; quite a large number.

> ... and is there enough disk space free where your GISDBASE is?

   18G free.

>>   Also, what guidelines does one apply to determine an appropriate
>> threshold value for an exterior watershed basin?

> That depends on your question, how detailed the extracted stream network
> and basins should be. Given a minimum total catchment area (TCA) to start
> a stream, the threshold would be TCA / (nsres * ewres), translating
> catchment area to number of cells.

   OK. Please explain 'exterior watershed basin' in the context of
r.watershed.

Thanks,

Rich