Investigating Pompeii subsoil using geomatics and geophysics merged analyses

The archaeological site of Pompeii represents an exceptional context for the application of non-invasive and integrated investigation methods aimed at enhancing the understanding of both exposed and buried remains. This study presents the results of multidisciplinary research conducted in the Palestra Grande site, a large and strategically important complex within the Archaeological Park, where no systematic archaeo-geophysical investigations had previously been carried out. Within an ongoing research agreement involving academic institutions and the Park, the study combines UAV-based geomatics analyses and near-surface geophysical investigations to support archaeological interpretation and assessment of non-excavated structures. High-resolution multispectral UAV photogrammetry was employed to generate orthophotos and spectral index maps, enabling the detection of surface anomalies potentially related to buried features. In parallel, ground penetrating radar (GPR) and electric resistivity tomography (ERT) surveys were carried out along targeted grids and profiles to investigate the shallow subsurface and to characterize the geometry and physical properties of buried anomalies. A key contribution of this work lies in the systematic comparison and integration of surface-based geomatics results and subsurface geophysical data. Visual interpretation was performed within QGIS to evaluate correspondences and discrepancies between spectral anomalies and geophysical signatures. In addition, a semi-automatic quantitative approach based on cross-correlation analysis was introduced to enhance results, which is traditionally reliant on time-consuming manual post-processing. The results demonstrate a significant degree of complementarity between geomatics and geophysical methods within the shallow subsurface, while also highlighting the different sensitivities and depth ranges of each technique achievable in this specific case study. The integrated approach provides a robust framework for identifying areas of archaeological potential, optimizing the planning of future investigations and reducing the need for invasive excavation. Overall, this study underscores the value of multidisciplinary and multi-parametric methodologies for archaeological research and heritage management in complex sites such as Pompeii.