[GRASS-user] Re: problem using r.watershed

[Markus Metz]

On Mon, Mar 26, 2012 at 5:32 PM, Filipe Silva Dias
<filipesdias at gmail.com> wrote:
> Thanks, it took a while but it worked.

You are welcome to compare it to alternatives ;)

>
>
> On Mon, Mar 26, 2012 at 3:11 PM, Markus Metz
> <markus.metz.giswork at googlemail.com> wrote:
>>
>> On Sun, Mar 25, 2012 at 2:59 PM, Filipe Silva Dias
>> <filipesdias at gmail.com> wrote:
>> > Thanks. Out of curiosity and tried with Grass 7 with -m (and 30 m
>> > resolution) and I obtained this error message:
>> >
>> > r.watershed -m elevation=DemPT2 at Grass7 threshold=10000
>> > stream=streams
>> > SECTION 1 beginning: Initiating Variables. 5 sections total.
>> > SECTION 1a: Mark masked and NULL cells
>> > SECTION 1b: Determining Offmap Flow.
>> > SECTION 2: A* Search.
>> > SECTION 3: Accumulating Surface Flow with MFD.
>> > SECTION 4: Watershed determination.
>> > SECTION 5: Closing Maps.
>> > ERROR: Rast_make_random_colors: min (1) > max (0)
>>
>> Apparently no basins were determined, probably because the threshold
>> of 10000 for flow accumulation was never reached. Maybe the current
>> region was either too small or did not cover parts of the DEM DemPT2?
>>
>> BTW, if you want to try out GRASS 7 in a separate mapset, you don't
>> need to copy over the DEM if you just want to read it. Within the
>> mapset Grass7, the following commands should work:
>> g.region -p rast=DemPt at ETRS89
>> r.watershed elevation=DemPt at ETRS89 stream=stream threshold=10000 -m
>>
>> Markus M
>>
>> >
>> > Subprocess failed with exit code 1
>> > category information for [streams] in [Grass7] missing or invalid
>> >
>> >
>> >
>> >
>> > On Sun, Mar 25, 2012 at 11:49 AM, Markus Metz
>> > <markus.metz.giswork at googlemail.com> wrote:
>> >>
>> >> On Sun, Mar 25, 2012 at 12:30 PM, Filipe Silva Dias
>> >> <filipesdias at gmail.com> wrote:
>> >> > I switched the resolution from 30x30 to 100x100 and now it works.
>> >> > Problem
>> >> > solved.
>> >> >
>> >> >
>> >> > On Sun, Mar 25, 2012 at 11:12 AM, Filipe Silva Dias
>> >> > <filipesdias at gmail.com>
>> >> > wrote:
>> >> >>
>> >> >> I'm using GRASS 6.4.2 and I'm on Windows 7
>> >> >>
>> >> >>
>> >> >> On Sun, Mar 25, 2012 at 11:11 AM, Filipe Silva Dias
>> >> >> <filipesdias at gmail.com> wrote:
>> >> >>>
>> >> >>> Dear all
>> >> >>>
>> >> >>> I'm trying to run r.watershed on a ASTER DEM (with the size of
>> >> >>> Portugal)
>> >> >>> but I'm getting this error:
>> >> >>>
>> >> >>> r.watershed elevation=DemPt at ETRS89 stream=stream
>> >> >>> threshold=10000
>> >> >>> SECTION 1a (of 5): Initiating Memory.
>> >> >>> ERROR: G_malloc: unable to allocate 1515173064 bytes at
>> >> >>> init_vars.c:134
>> >> >>> Subprocess failed with exit code 1
>> >> >>> category information for [stream] in [ETRS89] missing or invalid
>> >> >>>
>> >> >>> What am I doing wrong?
>> >> >>>
>> >> As you figured out already, the region, i.e. number of cells was too
>> >> large. In order to run r.watershed with that region (Portugal at 30m
>> >> resolution) on Windows, you would need GRASS 7 and run r.watershed
>> >> with the -m option.
>> >>
>> >> Markus M
>> >
>> >
>
>