A Marine-Buoy-Mounted System for Continuous and Real-Time Measurment of Seafloor Crustal Deformation

Abstract

In this paper, we describe the development of a continuous real-time system capable of measuring seafloor crustal deformation using the global satellite navigation system (GNSS)/Acoustic technique and a moored buoy. A program developed was implemented on the buoy to automatically distinguish the onset of a direct acoustic wave even if that wave had been contaminated with reflected waves and to detect the true travel-times by onboard processing rather transferring raw waveforms to the ground base station. This onboard procedure contributed to reduce the data size over a satellite communication. We conducted an operations test for a total of 106 days and found that the acoustic ranging and data transmissions were frequently interrupted by an unstable power supply, resulting in only 21% of the transmitted data being received at the ground base station. Nevertheless, we did not find any problem with continuous acoustic ranging measurement except for the above-mentioned power supply failure.

GARPOS: Analysis Software for the GNSS‐A Seafloor Positioning With Simultaneous Estimation of Sound Speed Structure

“…Since each subcomponent of GNSS-A technique, i.e., GNSS positioning, acoustic ranging, and so on, has been well established, observers can combine them on their platform. Especially, GNSS-A is expected to be practicalized in the near future with an unmanned surface vehicle (Chadwell, 2016) or a buoy (e.g., Kinugasa et al, 2020;Tadokoro et al, 2020). Even in the case of the stationary observation due to small cruising speed, GARPOS may provide the solutions by making a slight modification in the prior variance-covariance matrix.…”

Developments of GNSS buoy for a synthetic geohazard monitoring system

“…The top three plots (Units 1-3) show the observed travel times from the transducer at the buoy to the three sea-bottom transponders estimated using the algorithm developed by the present project. 71) The middle three plots represent the positions of the transducer at the buoy. The positions of the transducer until November 25, 2020, were obtained by offline analysis using the PPP algorithm with precise orbits and clocks called as MADOCA (Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis), which was developed by the Japan Aerospace Exploration Agency (JAXA).…”

GARPOS: analysis software for the GNSS-A seafloor positioning with simultaneous estimation of sound speed structure

“…Since each subcomponent of GNSS-A technique, i.e., GNSS positioning, acoustic ranging, and so on, has been well established, observers can combine them on their platform. Especially, GNSS-A is expected to be practicalized in the near future with an unmanned surface vehicle (Chadwell, 2016) or a buoy (e.g., Tadokoro et al, 2020;Kinugasa et al, 2020). Even in the case of the stationary observation due to small cruising speed, GARPOS may provide the solutions by making a slight modification in the prior variance-covariance matrix.…”