Hi all,
I'm new to the list, so bear with me :)
I'm trying to carry out some kriging of some (x,y,v)
data set on to a
regular grid. I have read some of the literature, and
I think that
this would be a good option (I have also examined the
possibility of
interpolating using a TIN, but I feel a bit more
"safe" using a
statistical approach!).
In order to do my kriging, I need to have a model
semi-variogram, and I
thought about using gstat for this (from the command
line, no R
interfaces, my files are just ASCII (x,y,z) triplets).
Given that my
data files are huge (of the order of millions of
points), I selected a
region of interest, and tried to produce a sample
semi-variogram, with
views to fitting a model.
In gstat, I got something that resembles y=exp(x),
which looks
distinctly wrong. The semivariogram value is ever
increasing, and does
not reach a sill at all. This is strange, and rather
unexpected. I have
tried doing a log transform of the data, but the shape
of the curve is
mostly unchanged.
I would be very grateful if anyone could shed any
light on what this
variogram means, how I could make progress modelling
it and so on.
Many thanks!
Jos�
--
Jose L Gomez-Dans, Research Assistant
Bristol Glaciology Centre, Geographical Sciences/CPOM
University of Bristol, Bristol, UK
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