[GRASS-user] r.watershed: Problems Using

[Jarek Jasiewicz]

Rich Shepard pisze:
> 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.
>
not so large, I'd rather say moderate
>> ... 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.
it is the size (in cells number) of flow accumulation when r.watershed 
starts delineate streams
>
> Thanks,
>
> Rich
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