Evaluation of the effects of sound speed variation on the GNSS-A positioning accuracy of the new analysis software "GARPOS" using numerically simulated data
Abstract
The Hydrographic and Oceanographic Department of Japan Coast Guard has been conducting seafloor geodetic observations since the early 2000s using the Global Navigation Satellite System-Acoustic ranging (GNSS-A) observation technique. GNSS-A observation has revealed important tectonic phenomena such as the coseismic slip of the 2011 Tohoku Earthquake (Sato et al. 2011), interplate coupling in the Nankai trough region (Yokota et al. 2016), and slow slip events occurring near the Nankai trough (Yokota and Ishikawa, 2020). One of the main topics of GNSS-A data analysis is the extraction of the spatiotemporal variation of the underwater sound speed structure, which is one of the main error sources of GNSS-A observation. Currently, in our observation and analysis routine, a linearized inversion method that alternately estimates the acoustic velocity profile and the transponder positions (Fujita et al. 2006) is used to determine the global coordinates of the seafloor transponders. Yokota et al. (2019) improved the sound speed estimation in the method of Fujita et al. (2006) by implementing a pseudo-tomographic analysis that extracts vessel position dependent (shallow layer) and transponder dependent (relatively deep layer) components of the sound speed gradient. Recently, an analysis software that directly estimates the sound speed variation has been newly developed (Watanabe et al. AGU 2020). In this analysis software "GARPOS" (GNSS-Acoustic Ranging combined POsitioning Solver), a Bayesian approach is utilized to appropriately estimate the sound speed variation without overfitting.
We conducted a series of numerical experiments using the GNSS-A simulator (Yokota et al. 2015, JpGU) to evaluate the effects of sound speed variation on the positioning accuracy. Using the GNSS-A simulator, we produced synthetic GNSS-A data by configuring various sound speed field settings. In our presentation, we will evaluate the positioning accuracy and the sound speed structure determined using GARPOS by comparing the analyzed results with the transponder positions and sound speed structure that were configured in the simulations.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMG021.0012N
- Keywords:
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- 1209 Tectonic deformation;
- GEODESY AND GRAVITY;
- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY;
- 4302 Geological;
- NATURAL HAZARDS;
- 8107 Continental neotectonics;
- TECTONOPHYSICS