For mining exploration in geologically complex zones, there are several techniques, among them the seismic refraction, which studies the propagation of seismic waves produced artificially, establishing its relationship with the geological configuration of the subsoil.One of these techniques is the Generalized Reciprocal Method (GRM) which has been proposed for reconstruction of subsurface structures with lateral variations of velocity.This method depends mainly on a single parameter called the optimum distance.This optimum value presents uncertainties when this is determined.In this work, we proposed a robust mathematical way to find the optimal value in order to reduce uncertainties in such a way that a better delineation of the subsurface structures is achieved