Unmanned aerial vehicle-based surface PIV experiments at Surb Creek

An optimized application of a low-cost airborne surface velocimetry system is presented. The technique is described by measurements at Surb Creek (Canton Aargau, Switzerland). Here, revitalization works had been conducted mainly to improve the passage of fish and other aquatic organisms. Thus, the knowledge of velocities is decisive for biologists to rate the success of the project. On a reach length of 650 m surveying flights and a particle image velocimetry analysis had been performed. The remaining velocity error due to ortho-rectification for the example given is estimated to <0.01 m and the total error is estimated to be <0.1 m s(-1). The raster resolution is 0.5 x 0.5 m(2) with 50% overlap. The optimized system is capable to provide flow fields with high resolution in time and space-a high-potential tool for data acquisition in the field.