GEOSTATS: gaussian and spherical variograms -Reply
- A few comments in response to Don Myers recent mailing (I realize these
are tangential to his main points, but I thought people might be interested):
>>It is well-known (although perhaps not written down anywhere)For a reference that deals with this topic, check out:
>>that it is best to use at least a small nugget with a Gaussian
>>model otherwise the kriging coefficient matrix is likely to
>>be ill-conditioned, making the results very unstable (numerically).
Ababou, Bagtzoglou and Wood, 1994, On the condition number of
covariance matrices in kriging, estimation and simulation of random fields,
Mathematical Geology, Vol. 26, No. 1, pp 99-133.
Don also wrote:
>>Note that some software does exactly that however, SURFERActually, Version 6 (1995) of SURFER allows for spherical, hole,
>>uses a linear variogram model and the slope of the model has no
>>effect on the kriging weights (only on the kriging variances).
exponential, gaussian, quadratic and rational quadratic models as well as
the linear model. It is quite a sophisticated package these days.
Sean A. McKenna
Sandia National Laboratories ph: 505 848 0713
Geohydrology Department fx: 505 848 0605
PO Box 5800 MS 1324 em: samcken@...
Albuquerque, NM 87185-1324
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