High-resolution geomatic and geophysical techniques integrated with chemical analyses for the characterization of a Roman wall

The aim of this work is the characterization of an ancient Roman wall through high-resolution geomatic and geophysical methods. Chemical analyses were performed in order to better identify the constitutive material. The archaeological wall of pre-Trajan age, discovered in 2011, is decorated with mosaics and located in a subterranean gallery below the Trajan's Baths on the Oppian hill (Rome historical centre). The dataset was collected using a 3D high-resolution laser scanner for the reconstruction and analysis of the skin wall, a Ground Penetrating Radar (GPR) to investigate the inner core of the wall and chemical analyses to characterize the composition of plaster and mosaics. The joint interpretation of data collected with different methodologies demonstrates the capability of the proposed method to characterize the wall in terms of constructive materials and to detect fractures and discontinuities between materials. A classification of the intensity parameter was performed starting with a visual analysis of the textured model built from laser scanner data before comparing it with the georadar results and the chemical analyses of the constitutive elements of the wall. Fractures and discontinuities partially visible on the surface of the structure and present in the inner part were mapped combining laser scanner and georadar data. The obtained results show that the integrated interpretation of the proposed techniques can provide important information about composition, geometry of the wall, correlation between physical and mechanical parameters and an extensive mapping of fractures and anomalies embedded within the wall.