[GRASS-user] r.watershed and big files

Arno Gerretsen arno at agerrius.nl
Thu Sep 1 10:07:24 EDT 2011

Quoting Arno Gerretsen <arno at agerrius.nl>:

>> I guess so too. The first message indicates that the on-disk option
>> (-m flag) is used. One reason could be not enough free disk space to
>> create temporary files. BTW, there seems to be a cut'n paste error,
>> the first message should read "SECTION 1 beginning: ..." and not
>> "SECTION 3 beginning: ..."
> I probably forgot to copy the first part then. Let me try again with  
> the new knowledge about the maximum size. Hopefully that will  
> prevent these errors.

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.



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