DC resistivity imaging plays an important role for a wide range of applications related to the characterization of the shallow subsurface. Major developments have been made over the last two decades to improve acquisition systems as well as resistivity inversion. Nevertheless, large-scale data sets still represent a challenging task, in particular with arbitrary topography. In order to better take into account topography, we have developed a new 2.5D/3D tomographic inversion code. Two new formulations for the singularity removal have been proposed. The direct problem is solved in the framework of the Generalized Finite Differences Method, that allows the use of unstructured meshes yielding a fine represention of topography. The inversion code uses the adjoint state method to compute the gradient of the misfit function in a numerically efficient way, giving goodresults on synthetic data. First results on real data have shown the main subsurface structures, as well as several low resistivity zones possibly corresponding to fractured areas.
