Proactive 2D model-based scan planning for existing buildings

Creating a building information model (BIM) is known to be valuable during the life-cycle of a building. In most cases, a BIM of an existing building either does not exist or is out of date. For existing buildings, an as-is BIM is needed to leverage the technology towards building life-cycle objectives. To create an as-is BIM, field surveying is a necessary task in collecting current building related information. Terrestrial laser scanners have been widely accepted as field surveying instruments due to their high level of accuracy. However, laser scanning is a time-consuming and labor-intensive process. Site revisiting and reworking of the scanning process is generally unavoidable because of inappropriate data collection processes. In this context, creating a scan plan before going to a job-site can improve the data collection process. In this study, the authors have proposed a 2D proactive scan-planning framework that includes three modules: an information-gathering module, a preparation module, and a searching module. In addition, three search algorithms - a greedy best-first search algorithm, a greedy search algorithm with a backtracking process, and a simulated annealing algorithm - were compared based on 64 actual building site drawings to identify strength and limitations. The experimental results demonstrate that the greedy search algorithm with a backtracking process could be used to compute an initial scan plan and the simulated annealing algorithm could be used to further refine the initial scan plan. This paper will also introduce the results of a case study that deployed the proposed scan-planning framework. In the case study, the resulting 3D-point cloud that was generated based on the proposed framework was compared with the 3D point cloud created with data collected through a planned scanning process performed by a scan technician.