Validation of geometric data in HBIM implementation processes of Romanesque churches in Sardinia

The implementation of BIM methodologies for historical buildings presupposes not only the collection of data and information related to its geometric configuration and to the technical parameters of its constituent elements, but more generally the identification of those semantic values which make it part of the historical-cultural heritage shared in a specific context. It is therefore essential that the modelling objectives are explicitly defined in relation to the specific BIM uses required, in order to avoid risks of over-modelling. This paper proposes a process of geometric validation of building information models of high morphological complexity implemented through Scan-to-BIM procedures. By means of a controlled and interoperable workflow, a chain of software applications is defined that is able to determine the level of geometric accuracy (LOA) of the information model with respect to the numerical model derived from the point cloud. Two case studies of H-BIM modelling of historical monumental complexes dating back to the Romanesque period in Sardinia (Italy) are illustrated: the churches of Sant'Efisio a Nora (Cagliari) and Santa Maria del Regno (Sassari). In the discussion of the results, the need for a prior definition of modelling strategies in relation to the expected BIM uses is highlighted.