Remote-sensing hyperspectral imaging for applications in archaeological areas: Non-invasive investigations on wall paintings and on mural inscriptions in the Pompeii site

Abstract

Hyper-Spectral Imaging (HSI) is nowadays a well-established technology in the field of Cultural Heritage (CH), being acknowledged as a highly effective tool for accomplishing both non-invasive diagnostics and documentation of different typologies of polychrome artworks. Until recently, in CH field HSI technique has been mainly applied for investigating polychrome surfaces of small or medium size objects in museum collections, such as easel paintings, illuminated manuscripts or paper based artifacts. Conversely, the outdoor applications of HSI on large mural surfaces, wall paintings, frescoes and archeological assets are still mostly unexplored. This is due to the fact that the HSI systems designed for CH applications usually work at short-distance from the targets and can cover only limited size surfaces. To overcome this limitation, and to extend the applications of HSI to investigating mural paintings in external contexts, cloisters, ceilings, or assets in archaeological sites, a remote-sensing approach, based on the use of readapted avionic sensors, has been considered and tested in-field.This work illustrates the results of the measurements campaigns carried out in the archaeological site of Pompeii (Italy) by means of remote-sensing HSI technology. To this purpose, the high-performance prototype SIMGA, an avionic hyperspectral imager developed by Leonardo Company for earth-surface observations, was employed for the first time in an archeological context, within the framework of the wider project “Great Pompeii Project”. HSI measurements were performed on different types of wall surfaces, including mural paintings and mural inscriptions. On the wall paintings, the acquired HSI data proved to be effectively usable for identification of most of pictorial materials and for mapping their distributions. The presence of gypsum as marker of degradation phenomena could be detected and mapped. On mural inscriptions, the HSI data could be suitably processed to enhance some vanishing traits, hardly perceivable by visual inspection. The proposed approach provided evidence that HSI is a promising tool to retrieve some faded parts of partially lost texts of mural inscriptions in archeological contexts.