166AI-GEOSTATS: Standardised versus general relative semivariograms ?
- Mar 30, 2001Dear 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;
- 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
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.
Gregoire Dubois (Ph.D.)
Institute of Mineralogy and Petrography
Dept. of Earth Sciences
University of Lausanne
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