Large-Scale Particle Image Velocimetry to Measure Streamflow from Videos Recorded from Unmanned Aerial Vehicle and Fixed Imaging System

The accuracy of river velocity measurements plays an important role in the effective management water resources. Various methods have been developed to measure velocity. Currently, image-based techniques provide a promising approach avoid physical contact with targeted bodies by researchers. In this study, measured surface velocities collected under low flow and high conditions Houlong River, Taiwan, using large-scale particle image velocimetry (LSPIV) captured unmanned aerial vehicle (UAV) terrestrial fixed station were analyzed compared. Under conditions, mean absolute errors LSPIV from UAV shooting heights 9, 12, 15 m fell within 0.055 ± 0.015 m/s, which was lower than that obtained on video recorded (i.e., 0.34 m/s). derived photography at flight height 12 without seeding particles different densities slightly different, range 0.095 0.025 m/s. associated 32, 62, 112 0.46 m/s 0.49 0.27 m, 0.97 respectively. A 62 yielded best result. Moreover, we also demonstrated optimal appropriate interrogation area acquisition time interval 16 × pixels 1/8 s, These two parameters should be carefully adopted accurately rivers.