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  • Hgeodave@aol.com
    From: witebsky@csd.uwm.edu (Joyce Witebsky) To: Hgeodave@aol.com David, I follow the instructions that come with the software. If the software is an
    Message 1 of 4 , Feb 8, 2001
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      From: witebsky@... (Joyce Witebsky)
      To: Hgeodave@...


      David,

      I follow the instructions that come with the software. If
      the software is an extension to ArcView (it has an .avx extension) then I
      put it in the EXT32 subdirectory of ArcView. If the software is a script
      (it has an .ave extension) I open it in Notepad or another ASCII text
      editor and look at the instructions at the top of the file, which should
      have some information about attaching it to a button or menu option in a
      particular menu (View, Table, Project, etc.). (For instructions on
      compiling, running or attaching scripts to buttons or menus by
      "customizing" ArcView, look up: Scripts, Running in the ArcView Help,
      Index.) If the software is stand-alone (it has an .exe extension)
      double-clicking it will run it.

      Hope this helps,

      Joyce Witebsky
      witebsky@...


      On Thu, 8 Feb 2001 Hgeodave@... wrote:

      >


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    • Ar�. G�r. Fevzi AKBA�
      dear all, I new in geostatistisc and using gs 5.1 sofware. My question is especially about this sofware. When modelling anisotropic variogram I have
      Message 2 of 4 , May 6, 2002
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        dear all,
        I new in geostatistisc and using gs 5.1 sofware.
        My question is especially about this sofware. When
        modelling anisotropic variogram I have problems.

        The software only modelling geometric anisotpoy and
        gives major and minor range. Sill and nugget values is
        same. When I change the sill and range visual fits
        getting better but RSS values getting bigger.

        As I understand using this software modelling
        directional variogram is impossible.
        Thank you very much for your interest
        fevzi akbas

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      • fevzi akbas
        dear all, I modelled a semivariogram and then using this variogram parameter performed cross validation. The computer program gives cross validation results as
        Message 3 of 4 , May 26, 2003
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          dear all,

          I modelled a semivariogram and then using this variogram parameter performed cross validation.

          The computer program gives cross validation results as correlation coefficient between estimated and actual values. this value as I know must be close to one.

          Is there any value for correlation coefficient( for example 0,6 or 0,7 ) that can be selected as limit value choosing semivariogram models represent our study area.

          Any literature about this subject will be apreciated.


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        • Pierre Goovaerts
          Hello, I am afraid that your approach of using cross validation results to select the semivariogram model suffers from several limitations. 1. Cross validation
          Message 4 of 4 , May 27, 2003
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            Hello,

            I am afraid that your approach of using cross validation results
            to select the semivariogram model suffers from several limitations.
            1. Cross validation results depend on many parameters besides
            the semivariogram model, such as type of kriging, search strategy,
            and it is not obvious which parameter could be responsible
            for poor prediction scores.
            2. The correlation coefficient would be unable to detect a systematic
            bias in your prediction, hence measures like absolute prediction
            errors would be better suited.
            3. Test of hypothesis on correlation coefficients is built on
            the assumption of indepedence of observations which is not the case here.

            At best you could use cross validation scores to compare several
            semivariogram models (instead of focusing on a single one), so use
            this as relative instead of absolute measure. But several studies
            have showed that kriging results are quite robust with respect
            to small changes in the parameters of the semivariogram model.

            Regards,

            Pierre Goovaerts

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

            Dr. Pierre Goovaerts
            President of PGeostat, LLC
            Chief Scientist with Biomedware Inc.
            710 Ridgemont Lane
            Ann Arbor, Michigan, 48103-1535, U.S.A.

            E-mail: goovaert@...
            Phone: (734) 668-9900
            Fax: (734) 668-7788
            http://alumni.engin.umich.edu/~goovaert/

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

            On Tue, 27 May 2003, fevzi akbas wrote:

            > dear all,
            >
            > I modelled a semivariogram and then using this variogram parameter performed cross validation.
            >
            > The computer program gives cross validation results as correlation coefficient between estimated and actual values. this value as I know must be close to one.
            >
            > Is there any value for correlation coefficient( for example 0,6 or 0,7 ) that can be selected as limit value choosing semivariogram models represent our study area.
            >
            > Any literature about this subject will be apreciated.
            >
            >
            > --
            > * To post a message to the list, send it to ai-geostats@...
            > * As a general service to the users, please remember to post a summary of any useful responses to your questions.
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            >


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