HR: 0830h
AN: G21D-0297    [PDF]
TI: Examination on Repeatability of GPS/Acoustic Seafloor Positioning for the Reference Points deployed around Japan
AU: * Fujita, M
EM: masayuki-fujita@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1, Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Sato, M
EM: mariko-satou@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1, Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Yabuki, T
EM: tetsuichirou-yabuki@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1, Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Mochizuki, M
EM: moma@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, Univ. of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505 Japan
AU: Asada, A
EM: asada@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, Univ. of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505 Japan
AB: We have been developing a system for precise seafloor geodetic measurement with the GPS/Acoustic combination technique and deploying about fifteen seafloor reference points on the land-ward slope of the major trenches around Japan, such as Japan Trench and Nankai Trough. Each reference point has four sets of seafloor acoustic transponders placed in a square. The primary purpose of our observation is to detect and monitor the crustal deformation caused by the subduction of the oceanic plate near the plate boundary. At each point, we carry out a campaign observation with several days using a survey vessel of Japan Coast Guard and revisit it once or twice a year, though the weather condition often hinders sufficient data acquisition. The procedure of data analysis consists of following three different stages as a whole: (1) kinematic GPS analysis, (2) acoustic wave analysis to obtain round travel time between the transducer on board and seafloor transponder, (3) a combination of results from (1) and (2) to get the precise seafloor position. The analysis for (3) is performed by a linear inversion method based on the least squares estimation. Acoustic velocities are given from the CTD measurement as initial values and corrected in the process by using residuals of the travel time data. Using data from our reference points with comparatively many observation days, we examine repeatability of obtained seafloor positions. For this purpose, we divided data from one campaign epoch into independent subsets, each with one or two days, and compared the obtained coordinates. The best result shows a repeatability of several centimeters in the horizontal components for the averaged coordinates of four sets of stations.
DE: 1208 Crustal movements--intraplate (8110)
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2003 Fall Meeting