Detection of Ocean Surface Currents Using Vessel’s Position and Heading with a Moving Rotation Center

We investigate the extraction of ocean surface currents in the vessel’s sway direction using navigation records of GNSS position and heading. Sway velocity is conventionally calculated using the speed over ground, course over ground, and heading of the vessel. The sway velocity has been known to be a good proxy of the ocean current component in its direction. Since the position of the rotation center of heading is different from that of the GNSS antenna, the rate of turn should be taken into account to accurately estimate ocean surface currents. We demonstrate that the position of the rotation center depends on the vessel speed and propose a method which considers this dependence to correct the rotation effect in the sway velocity. At a time scale shorter than ∼10 min, the proposed correction reduced the standard deviation by ∼43% compared with the conventional sway velocity for a test vessel. The corrected sway velocity is thus expected to be more sensitive to ocean surface currents including tsunamis at this short time scale. At a longer time scale, the sway velocity was hardly affected by the rotation effect and well reflected ocean currents such as geostrophic currents.