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Vario: The vario application is used for calculating one- and two-dimensional experimental semivariograms. The package is not limited to just the classical semivariogram but will also calculate covariances, madograms, rodograms, cross- semivariograms, etc. Analysis of the calculated values through jackknifing is also an option. Three types of soft indicator data can be used with hard data to calculate the spatial continuity. The application displays the measure of covariance ((h)) versus lag.

This is a basic isotropic experimental semivariogram, where the dashed line represents the data set variance. The two legends identify 1) each line, and 2) the parameters used to calculate the experimental semivariogram.

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Here, four ansiotropic experimental semivariograms have been calcualted at the same time. While there are differences at longer ranges, the models are nearly identical at the range where the lags meet the variance. This suggests an isotropic semivariogram is justified.

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Experimental semiavriograms can be plotted in 18 directions (every 10o's), with varying half-angles. Using this method and block, data set anisotropies can quickly be evaluated visually.

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The results from the 2D calculations can also be gridded (using grid) and displayed using contour (or surface or block). Contour also has a convienient profiling tools allowing the user to view the conventional 1D experimental semivariogram in different directions very quickly.

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Sometimes data sets are small, and while you might calculate a reasonable looking experimental semivariogram, small changes in the model parameters, or the gain or loss of a data point, and have drastic results. This plot shows a jackknifed semivariogram (n experimental semivariogram are calculated removing a different sample (n = # of samples)) and 95% error bars show the probable range for the value of each lag estimate. If the range is narrow, one can have confidence in the results. If the range is wide, particularly for short lags, this strongly more data is needed.

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For more information: info@uncert.com Last Modified: October 2, 2014