[GRASS-user] r.watershed error

[Kurt Springs]

Thanks Markus,

Let me make sure I understand.  For best results I need to set the resolution to 10m for the 1/3 arcsec.  With the region set as it is (most of Northern New England) when I do this I run out of memory.  To over come this, I can set the region to just encompass just the NED13_01 subregion.  Would it look like g.region zoom=NED13_01 align=NED13_01?

Might this also solve another problem I am having with r.watershed.  When the various functions are run, I have the map, plus "stuff" in the NULL area out side the map region.

Thanks for the help.

Kurt
On May 24, 2010, at 4:37 AM, Markus Metz wrote:

> On Sun, May 23, 2010 at 8:10 PM, Kurt Springs <ferret_bard at mac.com> wrote:
>> Problem was the resolution it starts working when I set it to 100m.  The dem
>> is ~69 x 27 km.
> 
> Apparently, the dem has a resolution of 1/3 arcsec (~10m), maybe
> reprojected and resampled. With these extends, there would be about
> 186 million cells in the input map which is not a lot. I have
> successfully processed regions with ~250 million cells in memory and
> ~500 million cells in segmented mode. Make sure the current
> computational region matches the resolution of the input dem and the
> extends of the current computational region do not exceed the extends
> of the input map. Setting the computational region to a smaller area
> within the dem coverage is fine, as long as g.region -p align=NED13_01
> is used after adjusting the extends. A resolution of 100m throws away
> a lot of the information present in the original dem.
> 
> 
>> Thanks
>> On May 23, 2010, at 12:00 PM, Rich Shepard wrote:
>> 
>> On Sat, 22 May 2010, Kurt Springs wrote:
>> 
>> ERROR: G_malloc: unable to allocate 18446744070980740804 bytes at ...
>> 
>>                                       ^^^^^^^^^^^^^^^^^^^^
>> 
>> Any idea what I'm doing wrong?
>> 
>> Kurt,
>> 
>>   Look at the amount of memory your file wants to be allocated: several
>> Petabytes. How much area is covered by that DEM and at what resolution? Even
>> with GRASS compiled for large file support your file is _way_ too large.
>> 
>> Rich
>> 
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