Towards a Structured and Scalable Metadata Framework for Photogrammetric Documentation: Ontological Traceability and Practical Implementation

Photogrammetry is widely used in cultural heritage documentation for its accessibility, non-invasiveness and adaptability to objects of different nature and scale. Over the years, several projects have developed specific solutions to improve the accuracy and traceability of workflows, with approaches ranging from embedded metadata to manual annotation. Over time, the need for a shared semantic structure that can guarantee interoperability between tools and institutions has emerged in parallel in order to facilitate the integration and coordinated reuse of data in order to avoid a fragmentation that can be critical when a single project is articulated on multiple platforms or devices, making it difficult to maintain metadata consistency throughout the process. With these specific issues as a focus, this paper presents PODS (Protocol of Ontological Digital Survey), a semantic and scalable framework for the structuring of photogrammetric metadata, based on an extension of CIDOC-CRM and CRMdig. The model includes controlled classes and vocabularies to ensure semantic consistency, procedural traceability and machine-actionable representations. In addition to the implementation for semantic query, PODS has also been integrated into Omeka-S, through exportable RDF templates compatible with existing ontologies, such as BeArchaeo, to facilitate distributed operational use. The three reported case studies aim to illustrate the potential of the model with respect to different scales, tools and environments, with the aim of supporting semantic interoperability even in heterogeneous and uncoordinated scenarios.