Close-range methods for muon imaging applications: a case study from Italy

The employment of remote sensing (RS) survey methods, in particular of close-range methods, as part of the muon imaging process is becoming a topic of growing interest. Use of light detection and ranging (LiDAR) methodologies, like terrestrial laser scanner (TLS), together with the unmanned aerial vehicles digital photogrammetry (UAV-DP) and satellite data are proving to be fundamental tools to carry out a reliable muographic measurements campaign. The main purpose of this presentation is to show the importance of correctly plan TLS and UAV-DP field surveys for muon radiography applications. To this aim, a real case study is presented: the research of hidden tombs at the Volumni Hypogeum archeo-geosite (Umbria, Italy). A high-resolution digital terrain model (DTM) and three-dimensional models of the surface/sub-surface were created merging different RS survey methods. The muon flux transmission was measured using the MIMA detector prototype (Muon Imaging for Mining and Archaeology). The latter is a small tracker (0.5 x 0.5. x 0.5 m³) developed by the physicists of the National Institute of Nuclear Physics (INFN), unit of Florence, and the Department of Physics and Astronomy of Florence. The measured muon flux was compared to the simulated one, obtained using the three-dimensional created environment, to infer information about the average density of the studied target along the various LoS (line of sight). The study highlights the importance of correctly carrying out the TLS and UAV-DP survey to make reliable hypotheses and decisions throughout the muographic measurement campaign. Furthermore, we pointed out how the precision of the tridimensional data can bias the muon imaging results.