Determining the Optimum Altitude Parameter for River Surveying Using UAVs: Case Study on Jinae-cheon Stream

Abstract

River surveying plays an important role in planning, maintenance, and operation of river flood prevention. Thus far, direct surveying has been mainly performed in the field. However, river surveying using an unmanned aerial vehicle (UAV) was recently applied to the hydrologic field. A river consists of top, bottom, and sloped surfaces, and a long stream is generally formed following the flow of water. The photographic parameters of the UAV, including the flight altitude, must be adjusted as per the characteristics of a river. Therefore, in this study, we focused on estimating the optimal photographing altitude for river surveying. The Jinae-cheon stream area located in Jiphyeon-myeon, Jinju was used as the research site, and the flight altitudes for the images were tested from 50 m to 120 m, increasing the altitude every 10 m. The images were corrected afterwards using 10 ground control points, and the error was calculated using 38 reference points. Therefore, it was confirmed that the error appeared relatively large from 70 m, and at the bottom. Moreover, the error was generally positive for the riverbed. This study provides useful results to regulate the photographing altitude for river surveying, and the results can be employed with extensive studies on diverse rivers to establish the standard UAV parameters.