[GRASS-user] r.watershed and big files

[arno at agerrius.nl]

Hello,

I am trying to use the r.watershed function to calculate streams (rivers)
from elevation data. As long as I make sure that the GRASS region is not
too big things work fine, but in the end I would like to do the
calculations at the resolution of the elevation data.

Let me first clarify what I mean with big in this case. I can do the
calculations with regions up to 10000x10000 pixels, but above that I start
to run into trouble. My elevation data is about 80000x60000, so I guess
that is quite big.

So my first question would be: Is the file I try to process too big or has
r.watershed been run successfully on such big files?

>From the mailing list I understand GRASS needs to be compiled with large
file support to work with such big files. I am not sure if my version is, I
have tried in on Windows with the stable version 6.4 from the OSGeo4W
installer and on Ubuntu with the 6.4 version from their repository.

This is the error I got on Ubuntu while running r.watershed:

SECTION 3 beginning: Initiating Variables. 5 sections total.
WARNING: No such file or directory
WARNING: cseg_open(): could not write segment file
Floating point exception
WARNING: Subprocess failed with exit code 34817

Any advice on how to prevent this error?

Thanks,

Arno