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1. Introduction
Building information modelling (BIM) is first and foremost a communications tool and it is now the industry standard for managing the design and construction of complex architectural and engineering projects. In order to be an effective communications tool, BIM requires a common language that is shared by all members of the project team. This has resulted in the development of benchmarks to establish standards in the model authoring process. Specific to the focus of this paper, advisory bodies such as BIMFORUM, the British Standards Institution (BSI), CanBIM, and the US Institute of Building Documentation (USIBD) have all created BIM standards that prescribe different levels of geometric detail and associated information for different phases of a project. For the most part, these standards are created for new construction and do not easily transfer to BIM for existing buildings. Current standards focus on requirements for different phases of a new-build project such as concept, design, construction and operation – with little or no discussion of as-found modelling. In 2015 – as part of our on-going work at the Parliament Hill National Historic Site – Carleton Immersive Media Studio (CIMS) saw a need to create a unique set of benchmarks and a protocol for existing and heritage buildings that – while addressing the unique demands of modelling as-found conditions – was consistent with the AECO industry guidelines. More specifically, existing standards and guidelines do not address the fact that existing buildings may have limited information on materiality and assembly. Further, existing standards and guidelines do not offer benchmarks for modelling the deflection and deformation that characterize older buildings and infrastructure.
BIM for the Parliament Hill National Historic Site is authored with Autodesk Revit. The geometry for the models is based on point cloud data from laser scanning and photogrammetry. When point cloud scan data are not available, construction drawings, photographs, and other secondary sources are referenced. The source used for the modelling of each BIM element is noted in the dialogue box for that element – not unlike a footnote used for citing sources in an essay.
While over thirty BIM guidelines were reviewed during the research for this project, four proved to be particularly relevant for the first phase of development of the CIMS protocol....