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[ai-geostats] isatis expertise?

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  • acullma@gwdg.de
    Dear list, I am trying to compare kriging results from different geostats software. The sample size is smaller than 300, I use real data as well as simulated
    Message 1 of 2 , Apr 20, 2006
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      Dear list,
      I am trying to compare kriging results from different geostats software.
      The sample size is smaller than 300, I use real data as well as simulated
      values. The variograms are omnidirectional and not nested (a spherical and
      an exponential one). I started with ordinary kriging. While GSLIB and
      SAS give similar results (the differences are probably be due to numerical
      differences between solaris/fortran and windows/??), ISATIS keeps
      producing errors of the form

      ---------------------------------------
      Error during Kriging
      Rank of the point (in selection) = 331
      ....
      -> Inversion problem at rank = 3
      ---------------------------------------

      The error message changes with the kriging neighbourhood but seems to be
      indifferent towards changes in the sample size and semivariogram model.
      SAS and GSLIB don't even show matrix inversion problems when performing
      kriging using a global neighbourhood.
      I've been through the parameter files over and over but I can't find any
      mistake. But it's my first time with ISATIS, so I'm a little lost here.
      Anybody able to give me a hint on where I commit the mistake?

      Uh: Version is 4.0.6 for windows. And of course ISATIS works well for a
      different data set...

      Thanks,
      Dominik
    • Mark Sweeney
      Dominik As a first pass you should try looking for duplicate values. From my experience Isatis falls over when kriging with duplicate data. Isatis has a
      Message 2 of 2 , Apr 20, 2006
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        Dominik

        As a first pass you should try looking for duplicate values. From my
        experience Isatis falls over when kriging with duplicate data.

        Isatis has a useful function to remove duplicate data, it can be found
        in the "TOOLS" menu system.

        Regards

        Mark Sweeney

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        -----Original Message-----
        From: acullma@... [mailto:acullma@...]
        Sent: Thursday, 20 April 2006 10:24 PM
        To: ai-geostats@...
        Subject: [ai-geostats] isatis expertise?

        Dear list,
        I am trying to compare kriging results from different geostats software.
        The sample size is smaller than 300, I use real data as well as
        simulated
        values. The variograms are omnidirectional and not nested (a spherical
        and
        an exponential one). I started with ordinary kriging. While GSLIB and
        SAS give similar results (the differences are probably be due to
        numerical
        differences between solaris/fortran and windows/??), ISATIS keeps
        producing errors of the form

        ---------------------------------------
        Error during Kriging
        Rank of the point (in selection) = 331
        ....
        -> Inversion problem at rank = 3
        ---------------------------------------

        The error message changes with the kriging neighbourhood but seems to be
        indifferent towards changes in the sample size and semivariogram model.
        SAS and GSLIB don't even show matrix inversion problems when performing
        kriging using a global neighbourhood.
        I've been through the parameter files over and over but I can't find any
        mistake. But it's my first time with ISATIS, so I'm a little lost here.

        Anybody able to give me a hint on where I commit the mistake?

        Uh: Version is 4.0.6 for windows. And of course ISATIS works well for a
        different data set...

        Thanks,
        Dominik
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