[GRASS-user] r.watershed and big files

Arno Gerretsen arno at agerrius.nl
Fri Sep 2 03:06:47 EDT 2011

Quoting Markus Metz <markus.metz.giswork at googlemail.com>:

> On Thu, Sep 1, 2011 at 4:07 PM, Arno Gerretsen <arno at agerrius.nl> wrote:
>> I did another attempt to use r.watershed on my big file. This time I
>> compiled GRASS 6.4.1 from source code and made sure it was configured for
>> largefiles (--enable-largefile). However I still get errors from r.watershed
>> and it seems related to the segment file:
>> GRASS 6.4.1 (ML):~/grass/bin > r.watershed elevation=ML_elev
>> stream=stream_total accumulation=accumulation_total threshold=10000 --o -m
>> memory=2000
>> SECTION 1 beginning: Initiating Variables. 5 sections total.
>> WARNING: No such file or directory
>> WARNING: dseg_open(): could not write segment file
>> WARNING: Subprocess failed with exit code 136
>> Can anybody tell me what is causing this (and how I could solve it)? In this
>> case I was using a region of 19800x16200 pixels.
> I think the reason is that GRASS could not initialize a temporary
> segment file, maybe because of insufficient free disk space?
> dseg_open() s called relative late in the initialization process when
> a number of other segment files have already been successfully
> created. You could try to create a new GRASS database on a different
> partition with more free disk space and try r.watershed again.
> If possible, you could also try GRASS7 and run r.watershed --verbose,
> this will print out estimated disk and memory requirements (and is
> much faster than r.watershed -m in GRASS 6).

I am already using the partition with most disk space, there is about  
170 GB left.

I think I will give GRASS 7 a go and see if that helps.



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