In order to obtain an equation for calculating the earth resistance of a deep-driven rod in a horizontally stratified multi-layer earth, expressions for the potential in such a structure are derived and evaluated with reference to previously established expressions for the two-layer model. In addition, by applying a series of numerical test data (earth parameters) to the obtained equation, the behavior of earth resistance for a deep-driven rod in regards to the multi-layer problem is revealed through examination of the calculations. The eventual purpose of the equation derived here is to help the grounding designer obtain the earth resistance he requires by enabling him to more accurately estimate the depth of boring or the length of a rod even in a multi-layer situation.
