Integration of 3D Ultrasonic Tomography, Photogrammetry, and Mixed Reality for the Structural Assessment of the Marble Statue “Caino”

Increasingly often, museums and art galleries require non-invasive inspections of marble sculptures on the occasion of transfers or museum loans in order to detect any hidden micro-fractures or internal decay. In this regard, we carried out a complete and non-invasive internal assessment using ultrasonic techniques, to ensure the structural stability of the monumental marble statue “Cain” (Domenico Trentacoste, 1903) from the Galleria d’Arte Moderna (GAM) in Palermo, prior to a planned transfer. The chosen approach integrates high-resolution digital photogrammetry with 3D ultrasonic tomography (UST). Using a series of scripts developed in MAT-LAB and Python, we reconstructed an ultrasonic wave velocity model strictly constrained to the geometric shape of the artwork. The data acquisition process involved 370 measurement points, including sources and receivers, and among the possible source-receiver pairs, 520 paths were selected to ensure sufficient coverage of all parts of the statue. The results indicated an average pressure wave velocity of approximately 5000 m/s, and the tomographic inversion confirmed an exceptional compactness of the material without any critical internal defects. Because raw geophysical data can be difficult for conservators to interpret, we exported the 3D velocity model into Mixed and Augmented Reality (MR/AR) environments. This approach allows users to interactively explore cross-sections of the statue in real-time, offering a highly intuitive method for interpreting non-destructive testing data in conservation planning.