Imaging radar has been dramatically developed over the past decades enabling a better understanding of cultural heritage from a microwave perspective. Nonetheless, a dedicated survey and analysis of the performance of such technology in cultural heritage monitoring and management is required. In order to fill this gap, we first review the technology advance of imaging radar, including ground penetration radar, ground-based and airborne/satellite radar, in the focused cultural applications to grasp the development trend of these technologies. We then analyse the performance and limitations of imaging radar technologies based on their respective characteristics to facilitate the technology service in practical applications. Finally, we propose a flexible solution of imaging radar in cultural heritage through technical integration with pilot synergy applications in archaeological prospection and cultural heritage diagnosis and conservation.
As per the UNESCO definition, Cultural Heritage (CH) encompass artifacts, monuments, a group of buildings and sites, museums that have a diversity of values including symbolic, historic, artistic, aesthetic, ethnological or anthropological, scientific and social significance. Its preservation is increasing concern by society considering the important role that CH plays in the evolution of people and their culture. Focusing on tangible heritage (movable, immovable and underwater), spanning from single building and monument to archaeological ruins, sites and architectural complexes, up to cultural landscapes, a growing number of technologies have been applied in this cutting-edge field (e.g., Burns, 1991, Pavlidis et al., 2007, Reimann et al., 2018, Inomata et al., 2020, Orengo et al., 2020) and among them, remote sensing is becoming prominent (e.g., Aminzadeh and Samani, 2006, Hesse, 2010, Lasaponara and Masini, 2012, Masini et al., 2018, Xue et al., 2020). Compared with optical imaging and Light Detection and Ranging (LiDAR) approaches, however, the performance and feasibility of imaging radar, including in particular Ground Penetrating Radar (GPR), ground-based and airborne/spaceborne Synthetic Aperture Radar (SAR), for CH have not been fully assessed yet. These are often constrained by the complexity of radar signal processing and lack of specialized expertise in image interpretation, i.e. limitations that should be overcome with specific initiatives of training and skills development, towards a yet-to-complete effective technological transfer into practice (Tapete and Cigna, 2017a).
Summary and perspectives
A comprehensive, dedicated review and performance analysis of the microwave imaging radar, including GPR, GB-SAR and airborne/satellite SAR, in CH studies and applications is provided with the aim to address the current knowledge gap between what science has achieved in this field of remote sensing and what end-users could benefit from if these technologies were integrated and implemented in real-world case studies. Past investigations reveal the necessity of technological combination and interdisciplinary investigation (Chen et al., 2021a), in particular hitherto their synergies in CH applications are still rare and need to be further exploited.
Based on this evidence, a viable solution to facilitate the booming development of this cutting-edge direction is to combine all these technologies. GPR, GB-SAR and airborne/satellite SAR are intrinsically complementary based on their observation views (subsurface-ground-space eye) and for monitoring scopes (visible and invisible condition alteration), resulting into the optimized performance through technological integration, which has further been confirmed by the pilot synergy applications as shown in Fig. 6, Fig. 7.