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Fig. 4 | Earth, Planets and Space

Fig. 4

From: An approximate travel time calculation and a robust GNSS-acoustic positioning method using an MCMC technique

Fig. 4

Estimation results of Method-3 at KAMN on August 1, 2014. a Sea-surface platform positions when the acoustic signals were transmitted. The colors show NTDs subtracting the long-term fluctuation of NTDs estimated by Model-3. b NTD time-series. Purple plots show temporal fluctuation of NTD, the green curve shows the NTD modeled by the 3d B-spline functions, the red curve shows the long-term fluctuation of NTD modeled by the 4d polynomial function, and a black curve shows the NTD modeled by the long-term fluctuation and the shallow sound speed gradient. c–h posterior PDFs for the major unknown parameters: gray histograms demonstrate the PDFs obtained by Method-3, red curves show the Gaussian distributions equivalent to the PDFs of Method-3, black curves in c–e show the Gaussian distributions for the parameters estimated by Method-1, and blue curves in c–e show the Gaussian distributions for the parameters estimated by Method-2. The red, green, and orange vertical lines represent mean, median, and 95% credible interval

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