VERTICAL ELECTRICAL SOUNDINGS (VES): to perform subsurface resistivity measurements in the event that the layering is flat and parallel, the Vertical Electrical Sounding technique is used (VES): this involves a series of measurements of resistivity carried out with increasing progressive distance between the current electrodes (dipole A-B or C1-C2) and potential (dipole M-N or P1-P2), according to a device with four electrodes (among the most common the Wenner quadripole and the Schlumberger quadripole).

Measurements are normally obtained by applying a direct current to the two A-B electrodes and measuring the corresponding voltage between the two M-N electrodes.