Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. In order to reduce the recording time in the field, an alternative is the use of several single GPR antennas in parallel (a ‘modular system’). Although this does not match the fast acquisition of detailed data sets by means of multi-channel arrays, a system consisting in single antennas can gradually be expanded and investment can be spread over time. This paper presents a 2D and a full-resolution 3D survey, conducted with a modular GPR instrument. A characteristic of these systems is that the cross-line separation between transmitter-receiver pairs is larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, for 3D data collection, profiles have to be acquired between previously recorded ones, which requires high positioning accuracy. A completely identical response for different single GPR antennas is difficult to achieve. For the system tested, on less favourable soils this resulted in striping in the horizontal slices. Several methods (3D frequency-wavenumber filtering, eigenimage filtering, mean profile filtering and filtering based on discrete wavelet transform, discrete ridgelet transform and linear Radon transform) were applied to two data sets exhibiting different kinds of linear noise and their capability to suppress artefacts was assessed. Although overall a reduction of the stripe patterns was achieved, mostly it was impossible to fully eliminate the noise in the time-slices without low-pass filtering in the cross-line direction. For the 2D data, low-pass filtering caused loss of some of the archaeological response and therefore was not applied. Mean profile filtering allowed the most reliable characterization of the archaeological structures

We present an approach for the estimation of ore processing residue volumes in historical mine waste dumps by the use of different geophysical methods in combination with mineralogical investigations. The stamp mill dump in the Harz mountains, Germany was examined with the methods electrical resistivity tomography (ERT), ground penetrating radar (GPR) and spectral induced polarization (SIP) flanked by mineralogical studies at many drilling points. The mineralogical results were used to calibrate the geophysical results and to distinguish between valuable and non-valuable waste material. With SIP we investigated individual profiles and took lab samples. These lab results emphasize the differences between the fine-grained tailings of clayey silt to silty sand in the top layer and the sandy tailings underneath in both resistivity and phase. From the GPR results we can distinguish between different layers and various backfillings in the first two meters due to the much higher resolution than the other methods. From ERT we achieved an overview about the dimension and inner structure of the dump and the boundary between the sandy residual material and the host rock. To estimate the volume of the residual body we carried out 2D inversion of all ERT profiles followed interpolation between the inverted profiles. From the drilling interpretation, the SIP lab results and the ERT field measurements we defined a resistivity threshold of 350 ohm-m for the ore processing residues to achieve a 3-dimensional body of the dump. The volume of this body was then corrected by a factor due to consideration of uncertainties, e.g., forest areas, inaccessible dump sections, small-scale anomalies (geological or different anthropogenic nature) and inversion coverage. As a result, we were able to calculate the volume of the ore processing residues which can be used further for the determination of the economic potential (remaining metal content).

The southern Harz Mountains are located on the northern periphery of the Latène culture, which was organized around central sites. Here, towards the end of the second century BC, settlements of the Przeworsk culture appear that provide evidence of a process of migration into a limited 'cultural island'. In this archaeological context we have used large-scale magnetic mapping and electrical resistivity tomography to determine localities where subsequently archaeological excavations were carried out. Magnetic prospecting has been performed with a multisensor gradiometer array mounted on a cart. Using a newly developed multichannel data logger LEA-D2 supporting a GPS unit for accurate real-time positioning, high-resolution measurements with a rate of more than 1 ha h −1 became possible. Electrical resistivity tomography has been carried out over selected sites to gain additional information on the subsurface from a different perspective.

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The study investigates a site of a former camp from the time of National Socialism in Berlin (Germany). After the second world war, the study area was also part of the former Berlin Wall complex. Two different radar array systems, an impulse and a step-frequency radar, were applied to the area and compared. Both radar arrays complement each other in their results and allow a differentiated data view. In connection with other sources, the former camp site Blankenfelde could be reconstructed in great detail.