We report on four case studies applying wave celerity to depth inversion – a method called Wave Kinematics Bathymetry (WKB) that we introduced to the hydrographic community in Shallow Survey 2018 (St John’s, Newfoundland).
WKB bathymetry is suitable for high turbidity coastal areas and complements the better-known satellite derive bathymetry (SBD) used where water is clear for bottom visibility.
WKB infers wave motion within the 2 s time interval between two near-IR spectral bands of the European Sentinel-2 satellites. We use all the images archived since 2017 (at 5-day repeat intervals). Hundreds of depths estimates are combined in ‘point clouds’ to improve depth accuracy. The nominal depth range is 0-20 m; 0-35 m in exceptional conditions.
The latest developments are further validation and demonstrations of various applications. (1) Perth, Australia. The WKB 90% confidence depth uncertainty was derived using LiDAR bathymetry as ground truth. (2) Newport, Oregon. A Jet Ski echo-sounding survey was ground truth. (3) Suriname. Here WKB tracked the movement of the Amazonian mud banks to 40 km from the shoreline and mapped erosion and accretion rates (~25 cm/year). And (4) Golfe d’Arguin, Mauritania. WKB accuracy at the edge of a shoal is validated with charts from the 1962 survey by French hydrographer Jean Bourgoin. (The survey covered the area of the 1816 Medusa shipwreck.) Nearby, WKB revealed an uncharted 8 m deep reef with a string of very shallow mounts.
A paper in press for the Proceedings of Oceans Conference (San Diego, September 2021) gives a fuller account of the Golfe d’Arguin bathymetry. A preprint handout will be available at the Remote Hydrography conference.
The author’s 45+ year career in remote sensing R&D with various sensor modalities and applications included underwater acoustics, marine radars, airborne IR imaging, radar altimeters, and multispectral satellites. He is the inventor of a WKB algorithm for inverting ocean wave images into bathymetry (US Patent 8903134, Methods for mapping depth and surface current).