Photogrammetry and 3-D Ultrasonic Tomography to estimate the integrity of two sculptures of the Egyptian Museum of Turin

We present a fruitful combination of geophysical tests (Ultrasonic Measurements) and photogrammetric processing (Structure from Motion) for the analysis of the integrity of a couple of statues from the Egyptian Museum of Turin. Aim of the study was to investigate the persistence of the exterior widespread fractures within the sculptures. More than one hundred ultrasonic measurements were acquired on selected travel-paths across each statue, using an ultrasonic pulse velocity instrument. Dealing with complex-shape objects of restrained dimensions, it was very important to accurately define the three-dimensional coordinates of sources and receivers, in order to precisely measure their distances. A 3-D model of the statues was obtained from photogrammetric techniques. The acquired data were analyzed with both a statistical approach and tomographic processing, comparing the use of classical and staggered grids, in order to obtain the best fit of the local resolution. The final results revealed a valuable tool to guide the procedures for the mobilization, transport and restoration of the sculptures.