2003 Volume 9 Pages 55-60
River surface elevation during flood is randomly deformed by the pressure fluctuation due to turbulence with various scales. This phenomenon is recognized as water surface ripples with numerous specular reflections when viewed from an oblique angle. We can assume that these surface ripples are convected with surface flow and usable as a kind of tracer for measuring velocity distribution when the wind effect is negligible. In this paper, a novel image analysis method for velocity measurement by using space-time image that indicates velocity information as its image orientation is proposed. The performance of the new method was verified with a synthetic space-time image. The method was then applied to some actual flow images. It was shown that the proposed method is superior to the method previously developed by the authors with respect to accuracy and robustness to noises.
