Very-high-resolution electrical resistivity imaging of buried foundations of a Roman villa near Nonnweiler, Germany

Electrical resistivity tomography (ERT) methods have been increasingly used in various shallow depth archaeological prospections in the last few decades. These non-invasive techniques can save time, costs, and efforts in archaeological prospection and yield detailed images of subsurface anomalies. We present the results of quasi-three-dimensional (3D) ERT measurements in an area of a presumed Roman construction, using a dense electrode network of parallel and orthogonal profiles in dipole-dipole configuration. A roll-along technique has been utilized to cover a large part of the archaeological site with a 25cm electrode and profile spacing, respectively. We have designed a new field procedure, which used an electrode array fixed in a frame. This facilitated a very efficient field operation, and overall a total of 9648 electrode positions were occupied. The 3D ERT inversion results clearly characterize the main structures of the Roman foundations. We compared our high-resolution 3D electrical resistivity model with findings from archaeological excavations, which have been done in some parts of the surveyed area. The ERT result coincide well with the excavation results, i.e. the location as well as the vertical and horizontal extensions of the structures could be precisely imaged. The ERT results successfully images most parts of the walls, pits and also smaller internal structures of the Roman building; moreover, excavation ditches that had been refilled prior to the ERT survey are delineated as resistivity heterogeneities as well.