The Certosa di Pavia Digital Ecosystem: A Massive Multi-Scale Digitization Framework Integrating 3D Survey, HBIM, and VR for Long-Term Preservation and Knowledge Dissemination

Digital technologies have significantly advanced documentation, management, and dissemination of Cultural Heritage (CH) through reality capture, Heritage Building Information Modelling (HBIM), and Extended Reality (XR). However, the digitisation of large and historically stratified heritage sites still relies on fragmented workflows that compromise interoperability and interrupt the continuity of geometric and semantic information throughout the heritage lifecycle. This paper proposes and validates a platform-independent, ecosystem-based methodology integrating multi-scale reality capture, hybrid Scan-to-HBIM modelling, semantic information management, interoperability, and XR within a continuous digital workflow. The methodology was validated through the large-scale digitisation of the Certosa di Pavia, where more than 1500 terrestrial laser scans, over 200,000 photographs, and approximately 50 billion points were acquired across a monumental complex covering nearly 331,000 m2. The proposed framework reconstructs irregular architectural geometries with millimetre-scale accuracy (σ = 0.005 m) while preserving geometric reliability, semantic consistency, and information traceability across point-cloud processing, HBIM environments, Common Data Environments (CDEs), and XR applications. The results demonstrate that the effective digitisation of complex CH depends not only on the accuracy of individual technologies but also on their coordinated integration within interoperable digital ecosystems. The proposed methodology provides a transferable framework for preserving knowledge continuity throughout the heritage lifecycle, enabling HBIM to evolve from a geometric representation into a dynamic knowledge environment supporting conservation, management, research, education, and public dissemination.