Autocorrelation and Geostatistics - Geomathematics: Theoretical Foundations, Applications and Future Developments - page 222

Fig. 6.19 Hypothetical autocorrelation function consisting of two negative exponentials to
incorporate nugget effect over short lag distances h with h < 2 m. Autocorrelation function for
nugget effect is superimposed on negative exponential curve for distances h 2m.(a) Vertical
scale is linear; (b) Vertical scale is logarithmic (Source: Agterberg 2012 , Fig. 12)
and this is significantly larger than 0.56 predicted by the negative exponential curve
shown in Fig. 6.16a . Although this result is based on relatively few data and the two
half-samples were adjoining, it strongly suggests that autocorrelation close to the
origin is not adequately described by the curve shown in Fig. 6.16a .