Tomographic resistivity 3D mapping: filter coefficients and depth correction

In this paper further adjustments are presented regarding the method given by Cosentino et al. (1995, 1997) to construct rapidly 3D tomographic pictures from resistivity data. The purpose of the procedure (a filtered back-projection of the experimental data) is to obtain 2D or 3D pictures which match as closely as possible the geometry of the structures which are being investigated. In order to optimize the target some problems should be solved. Firstly, one should try to detect correctly the depth of electrical discontinuities (or anomalous bodies); secondly and not less important, one should try to determine the size as weIl the shape of the structures which are buried. In this paper we study the conneetion between the resistivity of the anomalous bodies and their effect on the apparent resistivity distribution. The results suggest that is best to optimize the values of the filters using also the negative values of the influence coefficients; they give also some information which appear useful to improve the estimate of both the depth and geometry of the bodies.