GPR data processing for fractures and flakes detection in sandstone

GPR profiles acquired with 1.5 GHz antennae, on the main panels of Game Pass shelter, a major painted rock art site in the KwaZulu–Natal Drakensberg (South Africa), provide a better knowledge of sandstone blocks ready to detach and can help to precisely map the conservation condition of rock art panels. However, shallow rock wall discontinuities, such as flakes, fractures or joints comprised between 1 and 4 cm in depth, cannot be easily detected without specific GPR data processing. In this paper, we focus on the near-field zone, which contains a combination of reflections obscuring these coming from very shallow discontinuities. We propose an identification method for rock flakes, based on Monte-Carlo simulations, to obtain a probability of detection of the sought-after discontinuities or objects very close to the ground surface.