Computer-Aided Approach for Rapid Post-Event Visual Evaluation of a Building Facade

After a disaster strikes an urban area, damage to the facades of a building may produce dangerous falling hazards that jeopardize pedestrians and vehicles. Thus, building facades must be rapidly inspected to prevent potential loss of life and property damage. Harnessing the capacity to use new vision sensors and associated sensing platforms, such as unmanned aerial vehicles (UAVs) would expedite this process and alleviate spatial and temporal limitations typically associated with human-based inspection in high-rise buildings. In this paper, we have developed an approach to perform rapid and accurate visual inspection of building facades using images collected from UAVs. An orthophoto corresponding to any reasonably flat region on the building (e.g., a facade or building side) is automatically constructed using a structure-from-motion (SfM) technique, followed by image stitching and blending. Based on the geometric relationship between the collected images and the constructed orthophoto, high-resolution region-of-interest are automatically extracted from the collected images, enabling efficient visual inspection. We successfully demonstrate the capabilities of the technique using an abandoned building of which a facade has damaged building components (e.g., window panes or external drainage pipes).