The value of integrating Scan-to-BIM and Scan-vs-BIM techniques for construction monitoring using laser scanning and BIM: The case of cylindrical MEP components

10 There is a growing need for tools automating the processing of as-built 3D laser scanned data, and more 11 particularly the comparison of this as-built data with planned works. This paper particularly considers 12 the case of tracking MEP components with circular cross-sections, which essentially include pipes, and 13 some conduits and ducts. Discrepancies between the as-built and as-planned status of pipes, conduit 14 and ductwork result from changes that occur in the field and that are either unnoticed (human error) or 15 not reflected in the 3D model. Previous research has shown that the Hough transform, with judiciously 16 applied domain constraints, is a practical and cost-effective approach to find, recognize and reconstruct 17 cylindrical MEP works within point clouds automatically. Previous research has also shown that “Scan18 vs-BIM” systems that are based on the geometric alignment and comparison of as-built laser scans with 19 as-designed BIM models can effectively recognize and identify MEP components as long as they are 20