Estimation of flow discharge by an airborne velocimetry system
Martin Detert, Volker Weitbrecht · La Houille Blanche · 2016
A low-cost airborne velocimetry system has been developed and tested, consisting of an action cam, a quadrocopter, ground reference points, and seeding material. The obtained video frames were ortho-rectified and geo- referenced by computer vision techniques, with the by-product that each image got scaled as well. Flow velocity vector fields were determined using a particle image velocimetry algorithm covering a total reach length of 310 m. The data generally confirm depth-averaged velocity profiles obtained by a 3D acoustic Doppler current profiler. Flow discharges are estimated from that. For areas with homogeneous flow conditions we conclude that a correction factor of 0.85-0.9 should be applied to reduce surface velocities to depth-averaged velocities.