Re: AI-GEOSTATS: Standardised versus general relative semivariograms ?
- 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
> variance for each lag;
> and the
> - general relative semivariogram (Isaaks & Srivastava, 1989: An
> to applied geostatistics, page 164) where gamma(h) is standardised by
> the mean
> of each lag.
> Im currently analysing the spatial structure of radioactive deposition
> different levels with the help of indicators. Standardised & general
> semivariograms describe very well the structures while the semivariogram
> not really appropriate for such a highly
> skewed variable. For low values of the chosen thresholds, the
> semivariograms shows me a stronger spatial correlation compared to the
> relative semivariogram.
> For higher threshold values, the opposite situation appears.
> Would this mean that low values show strong fluctuations but that the
> value remains quite constant in space while high levels of radioactivity
> 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
> these are frequently used.
> Best regards
> Gregoire Dubois (Ph.D.)
> Institute of Mineralogy and Petrography
> Dept. of Earth Sciences
> University of Lausanne
> Get free email and a permanent address at http://www.netaddress.com/?N=1
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