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166AI-GEOSTATS: Standardised versus general relative semivariograms ?

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  • Gregoire Dubois
    Mar 30, 2001
      Dear all,

      can anyone point the relative advantages and drawbacks of

      - standardised semivariograms (See Pannatier, 1996: Variowin. Software
      for spatial data analysis in 2 D, page 39) where gamma(h) is divided by the
      variance for each lag;

      and the

      - general relative semivariogram (Isaaks & Srivastava, 1989: An introduction
      to applied geostatistics, page 164) where gamma(h) is standardised by the mean
      of each lag.

      I�m currently analysing the spatial structure of radioactive deposition for
      different levels with the help of indicators. Standardised & general relative
      semivariograms describe very well the structures while the semivariogram is
      not really appropriate for such a highly
      skewed variable. For low values of the chosen thresholds, the standardised
      semivariograms shows me a stronger spatial correlation compared to the general
      relative semivariogram.

      For higher threshold values, the opposite situation appears.

      Would this mean that low values show strong fluctuations but that the mean
      value remains quite constant in space while high levels of radioactivity show
      less fluctuations but the mean values change more in space ?. Has anyone
      experienced similar observations with other variables ?

      Apparently, there has not been much published on these functions, even if
      these are frequently used.

      Best regards

      Gregoire


      Gregoire Dubois (Ph.D.)
      Institute of Mineralogy and Petrography
      Dept. of Earth Sciences
      University of Lausanne
      Switzerland

      http://www.ai-geostats.org

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