ＵＡＶと水域可視化処理による河川地形計測手法の検討

抄録

Three-dimensional topographic UAV photo survey (UAV photogrammetry) is being utilized in public works owing to the spread of inexpensive and highly efficient UAV and powerful photogrammetry software. In this paper, we intend to examine the effectiveness of UAV photogrammetry on the river bed topography survey and bed material measurement. A field observation was conducted in the middle stream of Nagara river. The observed reach has cobble-gravel bar of a large area and wide range of water depth. To verify the accuracy of underwater topography measurement by UAV photogrammetry, actual bathymetry was measured using ADCP. Moreover, the measurement accuracy when using the underwater imaging process was compared to that when using the original process. UAV photogrammetry with the imaging process can reach greater depths of the underwater riverbed; however, the reflection of the water surface and turbidity block it considerably. 1.33 times (the refractive index of water) of water depth from UAV photogrammetry was in agreement with the actual bathymetry from ADCP measurement. These results demonstrate the required knowledge for employing UAV photogrammetry on the river.