where ,

Resistance

Thus, the apparent resistivity of the soil to a depth approximately equal to the spacing of the electrode can be computed. The resistivity unit is often so designed that the apparent resistivity can be read directly on the potentiometer.

In “resistivity mapping” or “transverse profiling” the electrodes are moved from place to place without changing their spacing, and the apparent resistivity and any anomalies within a depth equal to the spacing of the electrodes can thereby be determined for a number of points.