Surface currents retrieved from airborne video

Within this paper we describe a methodology to retrieve ocean surface currents from video data of ocean surface waves. The video sequences were acquired at nadirby an off the shelf quadcopterin the range of visible light. The quadcopteris equipped with an actively controlled gimbalfor stabilization of the video cameraand records all the information needed to geocodethe video data. The geocodedvideo sequences are used to measure surface waveproperties such as wave direction, length and phase velocity. These properties enable to measure the surface current, which results from the difference of the observed phase velocityto that given by the linear dispersion relation of surface waves. The method was applied to video data collected over the Elbe River in vicinity of a weir, showing the overall applicability.