Development of Aerial Space Time Volume Velocimetry for Measuring Surface Velocity Vector Distribution from UAV

¹ Graduate School of Engineering, Kobe University, 657-8501 1-1 Rokkodai, Nada, Kobe, Japan
² Department of Civil Engineering, Kobe University, 657-8501 1-1 Rokkodai, Nada, Kobe, Japan
³ CTI Engineering Co., Ltd., 1-6-7 Doshomachi, Chuo-ku, Osaka, Japan

^* Corresponding author: ifujita@kobe-u.ac.jp

Abstract

Due to the remarkable development of unmanned aerial vehicle (UAV) in recent years, its application in river engineering increases widely mainly for the measurement of ground topography such as by the technique Structure from Motion (SfM) using a series of high-resolution static images. However, although UAV usually installed a high density video camera, the use of the movie is limited just for watching and observing the geometrical feature of the ground. In the light of such a present status, the authors have developed an aerial space-time image velocimetry (STIV) technique to measure streamwise river surface velocity distributions. However, as STIV is insensitive to the change of flow direction, the aerial space-time volume velocimetry (STVV) technique, which is an extension of STIV, was developed in this research. STVV examines the change of volumetric texture within a space-time volume (STV) instead of examining the change of image intensity on a line segment as in STIV. The performance of STVV was investigated during the measurement of snowmelt flood of the Shinano River by comparing it with those obtained by the other techniques such as STIV, LSPIV and ADCP. It was made clear the aerial STVV has a great advantage over the existing image-based techniques.