[GRASS-dev] Re: v.krige.py Documentation
jeshua at OpenOSX.com
Wed Sep 2 18:23:47 EDT 2009
On Sep 2, 2009, at 6:05 AM, Anne Ghisla wrote:
> first of all thanks for testing v.krige. Your case study is very
> for v.krige improvement.
Thank you Anne for your efforts and reply.
>> Ultimately I need to be able to handle around a million points - not
>> looking like it will be possible based on my test.
>> Can anyone tell me what the required memory is based on? Is it based
>> on the region, the points, the block size, etc?
> On the number of points and on the region. They both contribute to
> create large intermediate and output objects.
> R memory usage use deserves some consideration: you can find
> here [0,1]. I know it is a limitation when handling large datasets: a
> good improvement for the code will be for example to store objects on
> the hard drive instead of RAM. Alternatively, v.krige could work on a
> slice of data at once, but I don't know if it is possible - worth to
> to Roger Bivand and Edzer Pebesma.
I am not very experienced with the Krig algorithm, perhaps someone
could offer some advice, however slicing it into tiles seems
problematic to me because I am under the impression that I need the
neighboring data for optimal interpolation.
>> Also, I can find very little documentation for it. For instance I am
>> not sure what the block size is used for, how is it different than
>> cell size set with g.region?
> Block size is a parameter used by block kriging, different from region
> resolution - see krige() documentation and examples .
>> It looks very interesting if I were able to actually use it.
>> The only documentation I can find for it is the man page and the wiki
>> page neither of which really address any of these questions.
> That's right - as v.krige is just a wrapper, its documentation should
> contain all useful pointers to the code it includes. Will improve this
Understood, thanks again.
>> Note that I can only run it from the command line, when I try to
>> the wxpython interface it displays a box for an instant and then
>> without any error messages.
> I suppose you run Windows: that's what happen when you use head
> of v.krige and an outdated revision of GRASS. The module is presently
> developed with develbranch_6, so needs recent updates (r38834 or
> higher). I plan to improve backward compatibility in the near future.
Actually I am on Mac OS X using 6.4 RC 5.
I checked out v.krig yesterday. Are you suggesting that it requires
GRASS 6.4 from SVN (I am not sure what is meant by r38834)?
Jeshua Lacock, Owner
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