Evolution of Rockfall based on SfM reconstruction of Street View and UAV data: Case study Kotopanjang, Indonesia

In regions where rockfall in a constant occurrence, understanding rockfall evolution becomes essential. Accurate information on the quantity of rock that happens can be obtained through historical data or primary data that can be compared between the two. The Koto Panjang area is a small local mine that is quite risky because it is on the side of the main road connecting access to the two provinces. This area is geologically included in Bohorok Formation composed of gravelly mudstone deposited during the Carboniferous - Early Permian period. Three rockfalls occurred in this area in 2015, 2016 and 2016, closing access for passing vehicles. To obtain historical data comparison, 164 images of data were collected from 360 street view panoramas ranging from 2015 - 2021. The data were extracted and converted into cube images using the decompose equirectangular panorama method, and then the images were processed using Agisoft to create point clouds and compared with the latest UAV data. Based on the comparison results, it was found that significant changes of up to 4,400m3 from 2015 to 2021 occurred at several points along this area. Kinematic structure analysis from direct measurement and 3D point cloud also showed the rockfall area predominantly with direct toppling and wedge failure, which caused the previous rockfall. Therefore, this method can help reconstruct area that have experienced rockfall and provide an understanding of the retreat evolution of rockfall in the area.