Observations of the surface current field in morphologically complex environments using drones

Abstract

This study aims to analyze the use of drones to measure surface currents and make it accessible via package of routines generated using free software. Validation was performed in a complex environment comparing the results with currents measured by acoustic Doppler current profiler (ADCP) and dye tracers. Then, we assessed the performance of the method at various altitudes and image resolutions. We found equivalent values obtained by the drone with dye tracers and ADCP, confirming the efficiency of the technique. However, best agreement with the dye tracer, as it provide velocity near the surface, which is more compatible with the data generated by the drone. On the other hand, ADCPs generate measurements around 1 m below the surface due to acoustic signal interference near the surface and the level of the transducers. The use of drones showed promise, agreeing with direct observations, and low sensitivity for video recordings at lower resolutions, thus reducing processing time. The implementation of the technique in Python enables its use on free software. Based on the comparisons, we highlight the need for future studies to test the efficiency of the drone method at different altitudes and camera inclination angles, which would enable larger data collection areas.