Figure 8.16a,b: These two graphs each show eighteen experimental semivariograms calculated every 10o from North with a) a 25o half-angle, and b) an 85o half-angle. Note that with increasing distance, the results become much "noisier", but this scatter is subdued with the larger half-angle (as one would suspect). Also note that both model have a range of about 1.4. This generally within zone of minimal scatter, so an argument could be made you using an isotropic model.