By Stephanie Ellen | Updated Aug 30, 2022
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A semivariogram is a key tool in geostatistics that quantifies spatial dependence between sample measurements. By plotting how similarity changes with distance, it informs decisions such as estimating average iron content across drilling sites.
Use a 100 ft × 100 ft grid—recommended by geostatistician Dr. Isobel Clark—to simplify calculations and provide a clear visual framework.
Enter the measurement at every grid intersection.
Locate all pairs of samples that are exactly 100 ft apart horizontally.
For each pair, square the difference between their values.
Sum all squared differences and divide by twice the number of pairs. The resulting figure is a semivariance point for 100 ft.
Repeat steps 3–5 for 200, 300, 400, 500, and 600 ft—stopping at roughly half the total number of samples.
On a graph, place distance (ft) on the x‑axis and the calculated semivariance on the y‑axis to visualize spatial correlation.
