Propagation of semantic information between orthophoto and 3D replica: a H-BIM system for the north transept of Pisa Cathedral

This contribution proposes a methodological approach for the transfer of annotations between orthophotos and 3D digital heritage models, relying on a mesh-based/point-based representation. The workflow leverages on the exploitation of 2D/3D projective relations and on the identification, propagation, modelling and tiling of virtual models of architectural heritage. Referring to the significant case study of Pisa Cathedral, the method is tested to ensure an informative continuum between 2D medias and 3D representations, in terms of morphology, geometry and semantic enrichment. At first, a high resolution ortho-photo is created to support studies related to conservation and restoration, e.g. to highlight degradation patterns and materials as well as to distinguish cracks, frescoed surfaces, decorations. Then, the information is translated from the 2D support to a virtual 3D mockup: this step is essential to ensure a complete understanding of the architectural heritage object, that can thus be studied in its entirety, considering its morphological complexities. The proposed approach provides a more effective system for the transfer and exchange of semantic information from high-resolution orthophotos to semantically rich 3D models, that can be fundamental even in view of the construction of Heritage-Building Information Modeling (H-BIM) environments.