Multi-Layered 3D Survey Process to Represent Visible and Invisible Data

Abstract. Over the last 25 years, active and passive 3D survey techniques applied in the Cultural Heritage domain have achieved a high degree of reliability. The degree of maturity in the integrated use of these methodologies is well exemplified by their broad application, across the public and private sectors. Nevertheless, surveying techniques able to acquire non-visible data (thermography, sonar, radar, etc.) related to wall packages, floors, foundations, etc.) remain little known in terms of data integration and representation. The latter in particular is crucial for the interpretation of signals at different frequencies that pass through the material, yielding responses that provide information on the type of material or on transitions between different dielectric properties. Often the experience has a basic role in understanding the significance of the maps and radargram, because it lacks the comparison and validation phase with the visible information. It leads to the paradox that to fully understand a complex architecture, analysing both its external and internal consistency, must be integrated data that presents different levels of uncertainty in its interpretation and representation, combining understandable information with others that require complex and non-immediate reading. The research work presented here focuses precisely on this dichotomy. Starting from heterogeneous data obtained from 3D laser scanners, photogrammetry, and ground-penetrating radar, this contribution offers a reflection on the management of this information and its possible integrated representation to make its interpretation more accessible, promoting its integration for a comprehensive understanding of the building.