[GRASS-dev] Re: v.krige.py Documentation

[Jeshua Lacock]

On Sep 2, 2009, at 6:05 AM, Anne Ghisla wrote:

> first of all thanks for testing v.krige. Your case study is very  
> useful
> 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  
> information
> 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  
> ask
> 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  
>> the
>> cell size set with g.region?
>
> Block size is a parameter used by block kriging, different from region
> resolution - see krige() documentation and examples [2].

Thanks.

>> 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
> asap.

Understood, thanks again.

>> Note that I can only run it from the command line, when I try to  
>> start
>> the wxpython interface it displays a box for an instant and then  
>> quits
>> without any error messages.
>
> I suppose you run Windows: that's what happen when you use head  
> revision
> of v.krige and an outdated revision of GRASS.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)?


Best,

Jeshua Lacock, Owner
<http://OpenOSX.com>
phone: 208.462.4171