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1281GEOSTATS: modeling the variogram

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  • Ulrich Leopold
    Jun 10, 1999
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      Hi all,

      I have some question concerning the modeling.

      I have calculated different variogram estimators.
      The traditional semivariogram reveals spatial continuity. But the
      shape, the ranges and anisotropies are better estimated by the more
      robust pairwise relative semivariogram.

      My questions are:

      (1) Could I model the experimental pairwise relative semivariogram
      (or other more robust variograms) or does it affect the
      kriging estimator and it's estimation variance considering the
      accuracy? And if yes do I have to standardize the sill to one?

      (2) Is there a difference between modeling the traditional
      semivariogram with it's original sill value and with a sill
      standardized to one.

      (3) What is really necessary to yield the correct estimates? Only the
      ratios of nugget and sill structures and their corresponding ranges
      or the real values provided by the traditional semivariogram with a
      non standardized sill?

      Goovaerts 1997 ("Geostatistics for natural resources estimation")
      warns against using the more robust estimators as substitutes for
      the traditional semivariogram. But for example Srivastava and Parker
      1989 ("Robust measures of spatial continuity") did model several
      robust estimators besides the traditional semivariogram.

      If a robust measure provides a better spatial continuity I would say
      that I can use it for modeling. Only the estimation variance will be
      affected and should not be taken as an absolute value but used in
      relative terms to compare the variances.

      Thanks in advance



      Ulrich Leopold

      Department of Soil Science
      The University of Trier

      E-mail: leop6101@...
      phone: 0049-(0)651-140764
      address: Engelstr.104, 54292 Trier, Germany
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