Advanced Processing Techniques for Step-Frequency Continuous-Wave Penetrating Radar: The Case Study of “Palazzo Vecchio” Walls (Firenze, Italy)

This article deals with different processing techniques applied to data gathered by a novel step-frequency penetrating radar in a measurement survey of the walls of the historical room “Salone dei 500” in Palazzo Vecchio (Firenze, Italy). The aim of the investigation was to detect discontinuities in the masonry walls, possibly corresponding to a cavity containing fragments of the lost fresco of the Battle of Anghiari by Leonardo da Vinci. Data have been processed by means of two different techniques. The first one is a time domain analysis compensating for dielectric losses inside the medium, and the second one is based on a one-dimensional inverse scattering approach. Even if based on different principles, both techniques reveal the presence of a discontinuity in the eastern wall of the room at a depth between 10 and 20 cm, whereas no discontinuity traces are observed in the other walls.