In this paper we consider the application of spatial estimation techniques to groundwater aquifer and geological borehole data. We investigate the adequacy of these techniques to reliably develop contour maps from various data sets. The estimator is developed theoretically in a simplified fashion using vector-matrix calculus. The practice of spatial estimation is discussed and the estimator is then applied to a groundwater aquifer system and a deep geological formation. It is shown that the various statistical models must first be identified from the data and evaluated before reasonable results can be expected.