How do you calculate a Semivariogram?

The experimental variogram is calculated by averaging one- half the difference squared of the z-values over all pairs of observations with the specified separation distance and direction. It is plotted as a two-dimensional graph.

What does a Semivariogram show?

The semivariogram depicts the spatial autocorrelation of the measured sample points. Once each pair of locations is plotted, a model is fit through them. There are certain characteristics that are commonly used to describe these models.

What is the use of variogram?

A variogram is a description of the spatial continuity of the data. The experimental variogram is a discrete function calculated using a measure of variability between pairs of points at various distances. The exact measure used depends on the variogram type selected (Deutsch & Journel 44-47).

What is a Covariogram?

Abstract. Covariogram is a term for covariance function of a second-order process and is instrumental for spatial interpolation. This article provides some examples of isotropic covariograms for stationary-spatial processes that have been used in kriging.

When does the MPE of a variogram become flat?

MPE includes several error components, FSE, GSE, TAE, and all ISEs, and hence is an appropriate measure of the absolute minimum error that can be expected in practice using the existing or the contemplated sampling scheme at hand. When the increasing variogram becomes more or less flat, the ‘sill’ of the variogram has been reached.

Which is the most important step in a variograpghic analysis?

The practical interpretation of the resulting variograms is the most important step in a variograpghic analysis. The variogram level and form provide extensive information on the process variation captured. Normally, only three primary types of variograms are encountered:

How is a variogram used in a geostatistical step?

The variogram is calculated and displayed in the principal directions. These experimental directional variogram points are not used directly in subsequent geostatistical steps such as kriging and simulation; a parametric variogram model is fitted to the experimental points.

How is anisotropy used to fit a variogram?

FIGURE 1. Typical variogram structures that are combined together in nested structures to fit experimental variograms. Anisotropy, that is, different directional variograms, are brought to the same distance units by geometric scaling.