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Good Day, Here are some points on the hole effect variogram model in
GSLIB. o. The cosine hole effect applied in GSLIB is only positive
definite (permissible) in ID.
Therefore it is required that the ranges in all other directions be set
as very large – this results in zonal anisotropy in the other directions. o. The sum or product of positive definite models is
positive definite. The dampened
hole effect variogram model is the product of the hole effect and exponential
covariance models. There is flexibility
in the choice of the dampening range,’d’. The assignment of ‘d’ based
on the range in the GSLIB code may have been in an effort to avoid the addition
of another parameter, which would have required a fair bit of coding. o. The range is the distance to the first peak in the hole
effect variogram model. Dampening
will attenuate the amplitude (with respect to lag distance) but will not affect
the wave length. I have written a paper on the hole effect. If you are interested contact me at the
address below. Hope this helps, Michael _____________________________________________ Ph.D. Candidate Department of Civil & Environmental Engineering -----Original
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AI-GEOSTATS: hole effect modeling in 3D Dear
list members, I
hope to get some insight into modeling and kriging with 3-D variograms where
all 3 directions display a pronounced hole-effect/oscillations. (I am using
GSLIB) First
of all, are there any permissibility issues regarding a hole effect model? I am thinking in particular of the
dampening factor, which is an additional parameter that is not accounted for in
the kriging parameter files. I know
that kt3d has a built-in relationship of d to the range, and I wonder if that
is just for simplification or because of permissibility contraints. Second,
what does the range mean for a hole effect model in terms of the maximum distance
between the estimation location and a contributing data location. Does the dampening affect this distance
in kt3d and would there be permissibility issues if I were to modify the
program? Third,
what if the dampening parameter is different in all 3 directins? And
finally, my grid will be discretized such that in one direction I will only
estimate at three different distances, and I assume that the semivariogram
model needs a good fit only at those lags.
Is this a workable assumption? I
much appreciate any insights into these questions!! Noemi
Noemi Barabas PhD
Candidate The
Dept.
Civil and Environmental Engineering 1351
Beal Avenue (13 EWRE) Phone:
(734) 615-5905 |
