The MYG methodology to carry out 3D electrical resistivity tomography on media covered by vulnerable surfaces of artistic value

Electrical Resistivity Tomography (ERT) is not yet frequently used in the study of walls, floors and foundations of buildings of artistic value, like Ground Penetrating Radar (GPR) or other commoner techniques, although it exhibits a great potentiality in terms of resolution power. The main limitation for the applicability of ERT to the Cultural Heritage field arises from the method of current injection: it is often necessary to drive current electrodes into small perforationson the acquisition surface in order to get a current flow sufficient to obtain a goodsignal-to-noise ratio. To overcome this limitation the Maximum-Yield Grid (MYG)methodology has been developed, in which only a small fraction (about 1/15) of the electrodes of the acquisition grid is used for current injection, with a significantreduction of the acquisition time as well. A case of study on media covered by precious mosaics is presented that refers to the main wall of the fountain hall of the Zisa palace of Palermo.