Consideration of positional uncertainty of sea-surface platform for GNSS-A seafloor positioning

As the unique approach to obtain centimeter-level seafloor positioning information, Global Navigation Satellite System-Acoustic ranging combination technique (GNSS-A) (Spiess, 1985) has drawn increasing attention and plays an important role in ocean engineering and marine geoscience research (Gagnon et al. 2005; Tadokoro et al. 2006; Watanabe et al.2014; Yokota et al. 2016; Yang et al. 2018).

GNSS-A positioning accuracy is significantly restricted by temporal and spatial variation errors related to propagation velocity of acoustic signals, the bridge medium to connect sea-surface platform and seafloor stations. Valuable investigations focusing on sound speed structure (SSS) modelling and inversion have been released and contribute to the GNSS-A performance improvements (Fujita et al. 2006; Ikuta et al. 2008; Honsho et al. 2017; Yokota et al. 2019; Watanabe et al. 2020; Yang et al. 2020; Yokota et al, 2022; Xue et al. 2023, in prep). It’s promising to progressively suppress SSS errors effect on seafloor positioning capability based on the increasingly refined SSS model policy.

Besides concentration on SSS errors modeling and corrections, additional consideration of positional uncertainty of sea-surface platform, one of vital parts of entire GNSS-A observation system, is reasonable for refined seafloor positioning policy. Currently, joint/total adjustment model and parameter estimation of the transducer and seafloor transponder for underwater precise point positioning have been published (Zhao et al. 2021). Furthermore, for seafloor geodetic network scene, numerical tests considering the positional uncertainty of sea-surface transducer were conducted. Further research may be hopeful to evaluate and control error propagation effect on seafloor positioning from sea-surface segment and helpful for usage of more flexible platform.