In this paper, a methodology has been proposed, according to which one can compute the parameters of the two-layer earth structure after carrying out a set of soil’s resistivity measurements. On that purpose, different optimization functions have been used. These optimization functions are the relative error, the absolute error, the square error, and the L-infinity norm. By comparing the results of each optimization function, the relative error is being proved to be the most suitable optimization function that gives the best fitting curve to the experimental data.