Our research analyses the potentialities and critical aspects resulting from the integration of BIM systems in the processes of survey, communication and management of the Built Cultural Heritage (BCH). It deals with the conceptual extension of “virtual model” triggered by BIM approach and its possibilities of stratifying knowledge.
The potential of BCH-oriented BIM systems (the so-called Heritage-BIM or H-BIM) is undeniable. However, there remain operational and theoretical issues related to the unresolved aporia between the rigidity of modelling tools and the high flexibility needed when BCH elements are involved.
Supported by some test applications carried out on case studies belonging to Sapienza main campus, our research aimed at defining a comprehensive approach for the implementation of BIM in the consolidated processes of survey, mainly referring to massive capturing technologies.
In the transition from the numeric model (point cloud) to the geometric one (synthetic and structured at semantic level too) this paper discusses the introduction of a new parameter, the Level of Reliability (LOR). This new factor intends to measure and explain the consistency of digital objects resulting from critical analysis and re-elaboration activities.
Current vagueness of standards together with the need for transparency in H-BIM modelling processes has led to the LOR as a possible solution to preserve the geometric correspondence and the ontological reliability of the model vis-à-vis the artefact it intends to represent. It describes, in fact, the level of global coherence of the process defining each element of the model and the model as a whole. The coding of a set of common and shared parameters makes it possible, finally, to achieve a synthetic numeric evaluation of the LOR, a sort of “score” for the model.
In this framework, the Level of Reliability may perhaps represent a relevant methodological step forward to “customize” BIM systems in order to make them more compatible with BCH issues. In other words, to encourage, support and implement the consolidated approaches that imply the gradual and deep knowledge of artefacts as a precondition for their conservation and enhancement.

di Carlo Bianchini, Saverio Nicastro - Sapienza Università di Roma