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GEOSTATS: Variogram calculation of irregular spaced data with GSLIB2.

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  • Octavi Fors Aldrich
    Hello everybody, I m novice using GSLIB2, and after taking a quicklook in the User s Guide, I ve missed one capability in gamv.f program. When calculating
    Message 1 of 6 , Jun 9, 1999
      Hello everybody,

      I'm novice using GSLIB2, and after taking a quicklook in the User's Guide,
      I've missed one capability in gamv.f program. When calculating variogram
      gamma(h) (whatever option you choose) it could be interesting to have h
      as a non-equally distributed distances array. Unfortunately, it
      seems that gamv.f outputs h as an equally-grided one. This is not
      important when number of points per lag is high, but not the same when
      it's low.

      I was wondering if anybody has "patched" this issue by adding some
      code lines to gamv.f. Any experiences?

      Thanks in advance,

      Octavi.

      =================================================================

      Octavi Fors Aldrich

      Astronomy Department
      Physics Faculty
      Avgda. Diagonal 647
      08028 Barcelona
      SPAIN

      Telf: 34-934021122
      Fax: 34-934021133
      e-mail: octavi@...

      =================================================================




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    • Ulrich Leopold
      Hi all, I have some question concerning the modeling. I have calculated different variogram estimators. The traditional semivariogram reveals spatial
      Message 2 of 6 , Jun 10, 1999
        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

        ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

        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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      • Mark Evans
        Hi. I m looking for a simple plug-in or extension for ARC VIEW in order to calculate some semivariograms for my forest landscape. ANyone know of any scripts
        Message 3 of 6 , Jul 8, 1999
          Hi.

          I'm looking for a simple plug-in or extension for ARC VIEW in order
          to calculate some semivariograms for my forest landscape.

          ANyone know of any scripts for download etc ?

          Thanks,

          Mark
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