Geodetic Seafloor Positioning Using an Unmanned Surface Vehicle—Contribution of Direction-of-Arrival Observations

Geodetic Seafloor Positioning Using an Unmanned Surface Vehicle—Contribution of Direction-of-Arrival Observations

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Precise underwater geodetic positioning remains a challenge.Measurements combining surface positioning (GNSS) with underwater acoustic positioning are generally performed from research vessels.Here we tested an alternative approach using a small Unmanned Surface Vehicle (USV) with a compact GNSS/Acoustic experimental set-up, easier to deploy, and more cost-effective.The positioning system included a GNSS receiver directly mounted above an Ultra Short Baseline (USBL) module integrated with an inertial system (INS) to correct for the USV motions.Different acquisition protocols, including box-in circles around catherine lansfield ombre rainbow clouds eyelet curtains transponders and two static positions of the USV, were tested.

The experiment conducted in the shallow waters (40 m) of the Bay of Brest, France, provided a data set to derive the coordinates of individual transponders from two-way-travel times, and direction of arrival (DOA) of acoustic rays from the transponders to the USV.Using a least-squares inversion, we show that DOAs improve single transponder positioning both in box-in and static acquisitions.From a series of short positioning sessions (20 min) over 2 days, we achieved a repeatability of ~5 cm in the locations of the transponders.Post-processing of the GNSS data turbo air m3f24-1 also significantly improved the two-way-travel times residuals compared to the real-time solution.