Figure 7.

Semi-variance function theoretical diagram. Nugget represents the variation caused by measurement or scale. Sill represents the sum of random variation and fixed variation. Partial Sill is the difference between Sill and Nugget. When the value of the semi-variance function is taken from the initial Nugget to the Sill, the interval distance of the sampling points is called the Range. The Sill effect (Nugget/Sill) is an important indicator of the degree of spatial autocorrelation; the smaller its value, the stronger the degree of spatial autocorrelation.