Title page for etd-0705113-104933


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URN etd-0705113-104933
Author Jing-zhong Ding
Author's Email Address m995080005@student.nsysu.edu.tw
Statistics This thesis had been viewed 5575 times. Download 338 times.
Department IAMPUT
Year 2012
Semester 2
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Effects of sound speed variation and measurement errors on the positioning of a seafloor transponder
Date of Defense 2013-06-19
Page Count 67
Keyword
  • bilinear model
  • linear model
  • sound-speed profile
  • positioning
  • seafloor transponder
  • GPS/Acoustic geodesy
  • Abstract Plate motions over the past few million years have averaged 110 centimeters per year. To monitor such slight deformations in the crust by the GPS/Acoustic geodesy, the accuracy on the order of a few centimeters in positioning seafloor transponders is required. Temporal and spatial variability of sound speed in the water column, however, as well as the measurement error of sound speed, is a main limiting factor in the production of accurate acoustic ranging even though frequent conductivity-temperature-depth (CTD) casts are made. Therefore, in this study, various geometrical options for acoustic ranging are designed in the numerical simulation of GPS/Acoustic geodesy and the effects of various sound-speed measurement errors on the accuracy of transponder positioning are evaluated. The simulation results show that observing slant-range measurements symmetrically around the transponder can nullify sound-speed errors in the horizontal but not vertical positioning of a seafloor transponder. Sound-speed errors produce the vertical positioning error although the slant-range observations are well geometrically balanced. For reducing the effect of sound-speed variation on the precision of GPS/Acoustic seafloor geodesy, this study proposes two synthetic sound-speed profiles of the water column, one linear and the other bilinear, to approximate acoustic travel-time measurements. The approximating sound-speed profile is used in combination with the tomographic estimation in GPS/Acoustic geodesy to estimate the sound speed variation, such that the effect of sound speed variation on the accuracy of transponder positioning is reduced. The performance of the two synthetic models is evaluated for different types of CTD-derived sound-speed profiles and for the acoustic ranging observations collected from a field GPS/Acoustic survey. The evaluation results demonstrate that both the linear and bilinear models can effectively reduce the effect of sound-speed variation on the precision of GPS/Acoustic positioning.
    Advisory Committee
  • Chi-Cheng Cheng - chair
  • Chau-Chang Wang - co-chair
  • Hsin-Hung Chen - advisor
  • Files
  • etd-0705113-104933.pdf
  • Indicate in-campus at 0 year and off-campus access at 1 year.
    Date of Submission 2013-08-05

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