Default Linear Variogram

The default linear variogram takes the form


where image\img00055.png is the unknown nugget effect, and image\img00056.png is the unknown slope. We need two defining equations to solve for these two unknown parameters.

According to theory, the expected value of the sample variance is the average value of the variogram between all possible pairs of sample locations (Barnes, 1991); this yields one equation. The second equation is generated by equating the experimental sample variogram for nearest neighbors to the modeled variogram. Thus, we can write



image\img00058.png = average distance to the nearest neighbor

image\davg.png = average inter-sample separation distance

image\img00060.png = one half the averaged squared difference between nearest neighbors

image\img00061.png = sample variance

By solving the two equations for the two unknown parameters, and checking for unreasonable values, we get the final formulae used in Surfer:


See Also

Creating a Variogram

Kriging and Variograms

Variogram Grid

Variogram Model

Variogram Overview