“…This is a task for which optical methods are best suited. Refractionbased reconstructions [37][38][39], stereophotography-based measurements [37,38,40,41], photogrammetry-based methods [42,43] (although restricted to steady flows), light absorption methods [44,45], stereo-correlation [46], stereo-refraction [47] and twin-camera refraction analysis of reflected laser light and PIV [48] have all been tested in attempts to capture moving water surfaces, each with their inherent drawbacks on requiring projected referenced grids, specific lighting, sophisticated and expensive equipment, and technical challenges in their setup and processing.…”