[GRASS-user] v.surf.idw G_Malloc

[Paul Kelly]

On Tue, 15 Jan 2008, Matthew James wrote:

> Hi Everyone,
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> New grass user J I?m using Grass 6.2.3 on windows using cygwin.
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> I am trying to generate yield maps. I have csv files containing x, y and
> yield columns.
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> The yields are calculated at random spots around the paddock.
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> In general these files can be many thousands of points long.
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> I?m first importing them into a vector file using v.in.ascii (seems to me
> that the process of importing such files needs to be documented better ?
> it?s hellish for a new user)
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> When I try to run v.surf.idw I get a ?G_Malloc ? out of memory error? ? this
> occurs almost instantaneously.

Please give the exact command lines you used for v.in.ascii and v.surf.idw 
as it is a bit hard to see what you are doing otherwise (also run 
v.surf.idw with --verbose in case it generates any useful messages).

Also are you importing the yield value as a z co-ordinate or a database 
field? For large numbers of points in general performance will be much 
much better if you avoid the database connection.

Also not building topology during the import (check the v.in.ascii man 
page; I can't remember the exact flag to use) will give a big performance 
boost for a large number of points. Unfortunately the version of 
v.surf.idw in 6.2.3 requires topology to be built to run - if you upgrade 
to 6.3 this is not required and you have a much better chance of being 
successfully able to interpret huge datasets with v.surf.idw.

Paul