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of v.krige and an outdated revision of GRASS.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
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