Mapping active faults by using small unmanned aerial vehicle and structure from motion software:

A case study on Midori fault scarp formed by the 1891 Nobi earthquake

Abstract

We photographed for the geomorphometry of the Midori fault scarp formed by the 1891 Nobi Earthquake in Motosu City, Gifu Prefecture (Japan) by using multirotor radio control helicopters as a small unmanned aerial vehicle (sUAV), and we analysed these images. A digital surface model (DSM) of 0.09 m mesh and an orthophoto with a resolution of 0.03 m were generated from these images by PhotoScan software produced by structure from motion (SfM). A topographic map with 1 m interval contours and a cross-section profile were processed using a DSM produced by ArcGIS. These results were compared with the same type of map and profile processed by LiDAR with a resolution of 5 m. The terrain was able to be measured by using the DSM derived by SfM with precision at least as high as that of the LiDAR. We expect that the new technology will be applied to tectonic landform survey and geomorphological research. In addition, our results should help to ensure flight safety and compliance with the law.