3:00 PM - 4:00 PM
[J07-P-02] Quantitative evaluation of error sources for the GPS-A seafloor geodesy
Seafloor geodetic observations using the GPS-Acoustic ranging combination technique (GPS-A) accomplished several monumental works in the fields of seismology and geodesy [e.g., Gagnon et al., 2005; Sato et al., 2011; Yokota et al., 2017]. In this technique, we observe using vessels on the sea around the seafloor acoustic mirror-type transponders. Seafloor absolute positions were determined using this acoustic data, the attitude data and the GPS data on the vessels. Although the GPS-A technique achieved establishment of the sophisticated seafloor observation network, an observation precision (1 σ = 2 - 3 cm: horizontal) remains lower than other geodetic observation techniques. The observation precision is affected mainly by three error sources. These are GPS errors, a measuring error between GPS and a bottomed acoustic transducer (T-D error), and an effect of ocean disturbances for undersea sound speed structures (SSS errors).
First, we performed a numerical simulation study to check reactions of a seafloor positioning analysis in several cases of the GPS errors and the T-D error. The obtained results suggested that the seafloor positioning in our present system is affected in 5 mm-scale (1 σ) by the GPS and T-D error sources.
Therefore, the positioning is affected majorly by the SSS error sources. We have reduced this effect using analytical approaches in this decade. In that process, spatial and temporal changes and spatial biases of SSS were approximated as fields modelled using high-order temporal functions. We review our current analysis flow and evaluate effects of ocean disturbances quantitatively.
Acknowledgements: We thank the Geospatial Information Authority of Japan (GSI) for high-rate GPS data for kinematic GPS analysis, and for daily coordinates of the sites on the GSI website.
First, we performed a numerical simulation study to check reactions of a seafloor positioning analysis in several cases of the GPS errors and the T-D error. The obtained results suggested that the seafloor positioning in our present system is affected in 5 mm-scale (1 σ) by the GPS and T-D error sources.
Therefore, the positioning is affected majorly by the SSS error sources. We have reduced this effect using analytical approaches in this decade. In that process, spatial and temporal changes and spatial biases of SSS were approximated as fields modelled using high-order temporal functions. We review our current analysis flow and evaluate effects of ocean disturbances quantitatively.
Acknowledgements: We thank the Geospatial Information Authority of Japan (GSI) for high-rate GPS data for kinematic GPS analysis, and for daily coordinates of the sites on the GSI website.