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Vertical electrical sounding

The vertical electrical sounding similarly to the method of electrical profiling is based on the four-electrode principle. The VES array consists of a series of the electrode combinations AMNB with gradually increasing distances among the electrodes for consequent combinations. The depth of sounding increases with the distance between A and B electrodes. The result of VES measurements with central-symmetric arrays is apparent (bulk) electrical resistivity as a function of half of the distance between the current electrodes, i.e. ER = f (AB/2) (Beck, 1981). The relationship between ER and AB/2 can be converted into a relationship between electrical resistivity and actual soil depth through a computer interpretation. Pozdnyakov et al. (1996a) developed programs for soil VES interpretations based on an updated R-function (Vanjuan and Morozova, 1962). We modified the conventional VES method for adequate evaluation of soil horizons by developing special arrays with smaller distances between electrodes. Other modifications of the traditional method included the reduced size and weight of electrodes, arrays with the fixed distances among electrodes, and automatic commutator for the electrode combinations. The equipment with such features allows measuring a detailed VES profile within about 15 min at one location.