Details

Autor(en) / Beteiligte

• Xie, Surui
• Zumberge, Mark
• Sasagawa, Glenn
• Voytenko, Denis

Titel

Shallow Water Seafloor Geodesy With Wave Glider‐Based GNSS‐Acoustic Surveying of a Single Transponder

Ist Teil von

• Earth and space science (Hoboken, N.J.), 2023-10, Vol.10 (10), p.n/a

Ort / Verlag

Hoboken: John Wiley & Sons, Inc

Erscheinungsjahr

2023

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Due to the blockage of seawater, seafloor displacement cannot be directly measured by space geodesy. The combination of Global Navigation Satellite Systems‐acoustic ranging (GNSS‐A) has been used to overcome the electromagnetic barrier, so that a GNSS‐determined sea surface vessel's coordinates can be transformed to seafloor benchmarks in a global reference frame. Due to the high cost and science priorities, previous GNSS‐A studies mainly targeted relatively deep water and a minimum of three transponders were used to form an array, equivalent to a precision geodetic station. With recent developments in unmanned autonomous surface vessels, low cost GNSS‐A surveys are poised to become practical. Here we demonstrate that with a carefully designed surveying trajectory, Wave Glider‐based GNSS‐A surveying of a single transponder in shallow water can provide centimeter‐level accuracy on horizontal seafloor positioning, even if the sound speed model deviates from the actual value by a few meters per second. Results from a nine‐month experiment conducted at ∼54 m water depth show that the repeatability of the seafloor horizontal positioning is better than 2 cm. When conditions allow, the acoustic observations should be collected symmetrically about the transponder and data redundancies are recommended to reduce the error associated with time‐dependent variations in sound speed. Plain Language Summary Seafloor geodesy is important for monitoring offshore strain processes. Global Navigation Satellite Systems‐acoustic ranging (GNSS‐A) uses sound signals traveling in water as rulers to measure the distances between the sea surface vessel and the seafloor sensor (transponder), so that the GNSS‐determined sea surface vessel's coordinates can be transformed to the seafloor through triangulation. Multiple transponders deployed on the seafloor are often needed to form an array so that noise caused by irregular variations in the sound signals can be reduced. In shallow water, due to the relatively short distance, the range distortion caused by a sound signal's refraction is smaller, and the time it takes to conduct each complete cycle of survey is shorter. These conditions allow the seafloor displacements to be measured with centimeter‐level accuracy using only one transponder. Key Points For single transponder Global Navigation Satellite Systems‐acoustic ranging in shallow water, seafloor vertical position estimation is sensitive to sound speed error and variation A geometrically symmetric surveying trajectory is preferable for error reduction in horizontal seafloor positioning Seafloor horizontal positions were measured with <2 cm repeatability at ∼54 m water depth over five repeat surveys with Wave Gliders