Multi-approach integration of ALS and TLS point clouds for a 3-D building modeling at LoD3

Registering, documenting, updating, revitalizing, expanding, and renovating old urban buildings require proper documentation. The adoption of 3D survey techniques is essential to grant efficiency and agility to such purposes. This article discusses a multi-approach integration of Light Detection and Ranging (LiDAR) data collected by aerial and terrestrial platforms, meant for the 3D modeling of a building at Level of Detail 3. The selected building presents challenging elements for modeling, such as blocks with different heights and indented facades. It is located on the campus of the Federal University of Paraná (UFPR) in Curitiba, Brazil, on a site with irregular terrain and surrounded by trees, what made the terrestrial laser scanning process difficult. For its three-dimensional reconstruction, data from an Aerial Laser Scanning system were integrated with data from a Terrestrial Laser Scanner (TLS). Based on the 3D modeling, an as-is Building Information Modeling model of the building’s exterior was created. To validate the results, measurements of the building were obtained by means of an Electronic Distance Measurement (EDM) device and they were then compared with measurements extracted from the point cloud-based BIM model. The results demonstrate that there was a correspondence between the EDM and the LiDAR-derived measures, attaining a satisfactory statistical agreement. The article focuses on the accuracy of LiDAR models for the cadastral update of buildings, providing information for decision making in documentation projects and construction interventions. The main contribution of this work consists in a multi-approach workflow for delivering an effective and precise solution for accomplishing an as-is BIM documentation, highlighting advantages, drawbacks, and the potential of this set of methods for integrating multi-source LiDAR point clouds.