The electrical geophysical methods are used to determine the electrical resistivity of the earth’s subsurface.
Electrical Resistivity Tomography (ERT) method is widely used in order to provide the true electrical resistivity of subsurface layers and derive their geometry into corresponding geological transactions.
Vertical Electrical Sounding(VES) method requires that four metal electrodes be placed with equal separation in a straight line in the surface of the soil to a depth not exceeding 5 % of the minimum separation of the electrodes. The electrode separation should be selected with consideration of the soil strata of interest. The resulting resistivity measurement represents the average resistivity of a hemisphere of soil of a radius equal to the electrode separation.