巻号一覧
54 巻 (2008)
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54 巻, 3 号
選択された号の論文の9件中1～9を表示しています
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藤田 雅之, 三浦 哲2008 年 54 巻 3 号 p. 111
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーPDF形式でダウンロード (139K) -
観測成果と新たな取り組み佐藤 まりこ, 木戸 元之, 田所 敬一2008 年 54 巻 3 号 p. 113-125
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーThree research groups, the Japan Coast Guard (JCG) and the Institute of Industrial Science, University of Tokyo, Tohoku University, and Nagoya University, have been developing precise seafloor positioning systems using the GPS/Acoustic combination technique and carrying out observations along the major trenches in the Pacific Ocean, such as the Japan Trench and the Nankai Trough. The primary purpose of seafloor geodetic observation is to detect and monitor crustal deformation caused by subduction of oceanic plates near the plate boundaries where huge earthquakes repeatedly occur. We have succeeded in detecting interseismic crustal movements and co-seismic displacements with centimeter resolution from multiple campaign observations. However, there still remain some issues in technical and operational aspects. Further efforts are necessary to achieve more precise and stable results.抄録全体を表示PDF形式でダウンロード (10310K) -
田所 敬一, 杉本 慎吾, 武藤 大介, 渡部 豪, 生田 領野, 安藤 雅孝, 奥田 隆, 木元 章典, 佐柳 敬造, 久野 正博2008 年 54 巻 3 号 p. 127-139
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーWe have developed a system for observin g seafloor crustal deformation combining the two techniques, acoustic ranging and kinematic GPS (Global Positioning System) positioning. We installed seven seafloor benchmarks at Suruga Bay and Kumano Nada along the Suruga-Nank ai Trough, Japan. We have performed repeated measurements of seafloor crustal d eformation for three benchmarks from 2004. The results for last three years provide horizontal velocities alo ng the Suruga-Nankai Trough, though the velocities present here are just preliminary ones. Tem poral and spatial variations of sound speed structure may cause large errors in the determined seafloor benchmark positions. To accomplish more accurate monitoring of the seafloor crustal defor mation related to the plate convergence, we should develop a positioning algorithm and o bservation strategy that can reduce the errors caused by the variations of sound speed in seawater.抄録全体を表示PDF形式でダウンロード (12064K) -
長田 幸仁, 水上 知子, 木戸 元之, 太田 雄策, 対馬 弘晃, 三浦 哲, 藤本 博己2008 年 54 巻 3 号 p. 141-151
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーWe have developed a GPS/Acoustic observ ation system to monitor seafloor crustal movement. This observation has two error sources: one is a long period spatial-temporal variation in the sound speed structure in the ocean, and the other is short period errors in the estimated GPS antenna positions caused by limited sampling rate of Kinematic GPS. We here focus on the latter problem. We test the effectiveness of a 10 Hz GPS receiver on the positioning of the acoustic transducer on the buoy. The difference of the position of the transducer estimated from the 1 Hz GPS receiver and that from the 10 Hz GPS receiver was -3 cm horizontally and -2 cm vertically, respectively. The towed buoy from the ship sways with an average frequency of 0.7 Hz or less judging from the attitude data. The sampling frequency of 2 Hz or higher is necessary to accurately monitor the antenna position. It was confirmed that the 10 Hz GPS receiver could reduce the short period error in the transponder's position. The high sampling GPS positioning is useful also for the reduction of the various period variations.抄録全体を表示PDF形式でダウンロード (8142K) -
武藤 大介, 田所 敬一, 杉本 慎吾, 奥田 隆, 渡部 豪, 木元 章典, 生田 領野, 安藤 雅孝2008 年 54 巻 3 号 p. 153-162
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーWe have developed a seafloor positioning sy stem composed of Kinematic GPS (Global Positioning System) positioning and acoustic ranging. We have accomplished about 2-3 cm ac curacy in each observation. Nevertheless, the accuracy of our system is still lower than that of GEONE T. Therefore we investigate main error factors of our system. In our system, we consider that temporal and spatial variations of sound speed structure are main factor of the positioning error. T herefore, we numerically simulated the system and evaluated the effect of these factors on posi tioning of seafloor benchmark. As the results, we found that temporal variation with any periods between 0.5 and 48 hour can be estimated in our algorithm, and the positioning error is smaller than 1 cm. On the other hand, we found that spatial variation inside the typical Kuroshio current causes the bias of 28-68cm.抄録全体を表示PDF形式でダウンロード (1840K) -
木戸 元之, 藤本 博己, 長田 幸仁2008 年 54 巻 3 号 p. 163-179
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーIn the GPS/acoustic measurement, it is crucial to monitor precise position of an acoustic transducer or a surface platform in motion as a rigid body. A GPS gyro with 1 Hz sampling is not sufficient to accurately describe the transducer motion especially for our past system that used a small buoy, which has been upgraded into 10 Hz sampling at present system. Although the past system was equipped with an extra motion sensor, the data were not in use due to its incomplete configurations: unmeasured installation position/angle and lack of time stamp in the data. To utilize this awkward but important data, we developed an algorithm to solve these ambiguities all at once. The algorithm reveals the sensor position within 2 cm, the sensor angle within 0.4°, and time lag within 0.02 s precisions. Applying motion sensor data with setup conditions obtained through the algorithm, we successfully interpolate the transducer motion combined with the 1 Hz GPS gyro, which greatly reduces scatter in the travel times of acoustic ranging.抄録全体を表示PDF形式でダウンロード (11854K) -
藤本 博己, 木戸 元之, 長田 幸仁, 金田 義行2008 年 54 巻 3 号 p. 181-187
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーGPS/Acoustic (GPS/A) seafloor positioning is a novel method for observation of a regional seafloor crustal movement, and is now most promising in the field of seafloor geodesy. Compared with land-based GPS observation, however, it has critical problems against on-line, continuous, and long-term observations as well as the limited accuracy of repeated positioning. It has recently been pro-posed that GPS/A positioning with five precision transponders can improve the accuracy of seafloor positioning with limited observation time. Since GPS/A positioning on a moored buoy combined with the new positioning method can be a solution to cope with the important problems, a stand- alone observation system is under development in preparation for a possible future application to the cabled seafloor observatory project DONET funded by the MEXT, Japan. It can be a gateway to semi-real-time seafloor positioning based on continuous GPS/A observation.抄録全体を表示PDF形式でダウンロード (7558K) -
望月 将志, 浅田 昭, 浦 環, 藤田 雅之2008 年 54 巻 3 号 p. 189-197
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリーInstitute of Industrial Science, University of Tokyo, has started the development of new-generation seafloor geodetic observation system. Central idea of this new system is to utilize technique of underwater robotics in place of using a research vessel that has been used in the current observation system. This new system will give us opportunities for observation with choosing favorable conditions of the sea and GPS satellite distribution, as well as much more frequent observations and flexible planning of observation in response to sudden geodetic events. The trials with the prototype of the new observation system have been conducted in Sagami Bay. The new system could locate the position of the seafloor transponder with the root mean square of the travel time (two-way) of 0.06 ms which corresponds to 4-5 cm in position. This indicates that the new system will reach to the higher level in performance than the current system in the near future. This result encourages us to move ahead on the completion of the new system.抄録全体を表示PDF形式でダウンロード (9542K) -
川崎 一朗2008 年 54 巻 3 号 p. 201
発行日: 2008年
公開日: 2013/02/25
ジャーナル フリー375ページのTable1において, 初期振幅に間違いがあり訂正する必要がある. 加速度は重力ポテンシャル項による寄与を含まないことを明示する必要がある. 以下に正しい表と表の説明を示す.抄録全体を表示PDF形式でダウンロード (72K)
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