Automated Spatial Change Analysis of Building Systems Using 3d Imagery Data

Changes of both designs and construction process usually cause spatial changes in facility design and challenges related to spatial change management between various building systems (e.g., Mechanical, Electrical, and Plumbing) and building components. In practice, design changes can be triggered by the needs of the owner, engineers and experts, resulting in spatial changes of as-designed objects and possibly spatial clashes between them. Spatial deviations also occur between the as-built conditions of building systems components and their asdesigned conditions. These deviations are due to changing environments, incomplete design information, and uncertainties in the construction workflows. Spatial clashes caused by changes and deviations need to be addressed through coordination among stakeholders from multiple trades. Such coordination can be tedious, especially when interwoven geometries of building systems components exist. Automated spatial clash detection algorithms are of limited help when the large number of objects interwoven in small spaces, as ambiguities about which points belong to which objects often occur within a space packed with a large number of building systems components. This paper examines the technical feasibility and scientific challenges of using 3D imaging technology (e.g., laser scanning) to support spatial change analysis of building systems. A review of existing studies indicates that the uses of 3D imaging systems enable civil engineers to acquire detailed as-built geometries frequently in the form of dense 3D point clouds, while posing challenges of handling 3D curvilinear geometries locating close to or even interwoven with each other. Using a case study, this paper shows that currently-adopted neighborhoodsearching-based analysis fails in detecting changes of 3D curvilinear objects packed in small spaces, and proposes to model the geometric and topological relationships among 3D curves as the theoretic basis of a robust spatial change analysis approach of building systems.