Abstract
AbstractTo overcome spatial and temporal limitations of sea surface height instruments such as tide gauges, satellite altimetry, and Global Navigation Satellite Systems (GNSS) buoys, we investigate the use of an unmanned, self‐propelled Wave Glider surface vehicle equipped with a geodetic GNSS receiver. Centimetric precision instantaneous sea surface height measurement is demonstrated from a 13‐day deployment in the North Sea, during which the glider traversed a track of about 600 km. Ellipsoidal heights were estimated at 5 Hz using kinematic GNSS precise point positioning and, after correcting for tides using the Finite Element Solution 2014b model and for the geoid using the Earth Gravitational Model 2008, hourly dynamic ocean topography measurements agreed with those from the UK Met Office Forecasting Ocean Assimilation Model‐Atlantic Margin Model 7 to 6.1‐cm standard deviation. Conversely, on correcting for the tides and dynamic ocean topography, 5.1‐cm standard deviation agreement with Earth Gravitational Model 2008 at its North Sea spatial resolution was obtained. Hourly measurements of significant wave height agreed with the WAVEWATCH III model and WaveNet buoy observations to 17 and 24 cm (standard deviation), respectively, and dominant wave periods to 1.4 s. These precisions were obtained in winds gusting up to 20 m/s.
Highlights
Centimetric precision sea surface height (SSH) measurements are needed for determining (1) the dynamic ocean topography (DOT), (2) the marine geoid, (3) the sea state, and (4) ocean tides
To overcome spatial and temporal limitations of sea surface height instruments such as tide gauges, satellite altimetry, and Global Navigation Satellite Systems (GNSS) buoys, we investigate the use of an unmanned, self-propelled Wave Glider surface vehicle equipped with a geodetic GNSS receiver
SSH has been measured by altimetry satellites (e.g., Wunsch & Stammer, 1998), tide gauges, and geodetic Global Navigation Satellite Systems (GNSS) receivers on buoys (e.g., Xu et al, 2016), ships (e.g., Foster et al, 2009), and catamarans towed by small boats (Bonnefond et al, 2003)
Summary
Centimetric precision sea surface height (SSH) measurements are needed for determining (1) the dynamic ocean topography (DOT), (2) the marine geoid, (3) the sea state (waves), and (4) ocean tides. Unmanned marine surface vehicles equipped with geodetic GNSS receivers provide a means to overcome the deficiencies of the aforementioned sensors and platforms, enabling centimetric precision SSHs to be measured anywhere globally, at any temporal resolution. One such unmanned vehicle is the Liquid Robotics “Wave Glider SV2” (hereafter WG), comprising a float able to house a solar-powered instrumentation payload, connected by an umbilical cable to a subsurface wings/rudder frame, with the differential motion between the float and subsurface enabling wave-powered propulsion of up to ~1 m/s (~2 knots). The potential applications of the GNSS WG instrument are discussed
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