Construction of 3D models of buildings damaged by earthquakes using UAV aerial images

Unmanned aerial vehicles (UAVs) are becoming very popular recently due to their accessibility to targets, promptness of dispatch, and high-spatial resolution of acquired images. In this study, the authors tried to obtain digital images from air and ground for a turned-down and washed-away building in Onagawa Town, Miyagi Prefecture, Japan due to the 2011 Tohoku earthquake and tsunami. A small multirotortype UAV was used in this aerial survey. Then 3D models were constructed in computer using the acquired images based on the Structure-from-Motion (SfM) technique. The most accurate model was made when both the aerial and ground images were used for 3D modelling. As the second example, an aerial video taken from UAVs was used to model affected districts in Kathmandu, Nepal, due the Mw7.8 Gorkha earthquake on April 25, 2015. The video was taken by the Canadian humanitarian organization and released on Internet. The 3D models were developed from the video footage, and they show the details of damage situation in the urban districts.