Abstract
This case study aims at development of a local remote sensing technology for measurement of surface flow field of rivers and rakes by means of PTV, Particle Tracking Velocimetry. Six thousand flat rice cakes with the diameter of 15 cm were scattered on the Uji river as tracers. A video camera mounted on a helicopter, hovering at the height of 300 m, took continuous images of the flow. Many problems associated with the practical applications of PTV to natural flow fields were picked up. Among them, there was a problem in identification of tracer images in that the computer software could not separate images of light reflections due to wind-driven surface tension waves from the tracer images. Countermeasures to the problems were proposed and tested. The surface flow field was analyzed by the PTV with the countermeasures, and compared with the flow field at 20-cm below the surface measured with an ADCP, Acoustic Doppler Current Profiler.
