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170Re: AI-GEOSTATS: Standardised versus general relative semivariograms ?

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  • Ulrich Leopold
    Apr 3, 2001
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      Dear Gregoire,

      there exists a publication which could be interesting for you:

      Srivastava, R.M.; Parker, H.M. 1989: Robust measures of spatial
      continuity. In: Armstrong, M. 1989 (Ed.): Geostatistics. Vol. I.
      Dordrecht, pp. 295-308.

      On 2001.03.30 14:23:44 +0200 Gregoire Dubois wrote:
      > 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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      --
      Ulrich Leopold
      Dipl. Geograph

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      Germany

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