深海曳航式３成分磁力計の開発
Deep-tow three component magnetometer (DTCM)の開発

２００１年

KR01-15「かいれい」単独調査航海にて

１９９８年

R/V AtlantisによるMOAI98航海にて


白嶺丸航海にて．

A newly developed deep-tow three component magnetometer

Nobukazu Seama and Michiko Yamamoto (Both at Graduate School of Science and Technology, Chiba University, Yayoi, Inage, Chiba 263, Japan; Phone: +81-43-290-2850; Email: seama@earth.s.chiba-u.ac.jp); Nobuhiro Isezaki (Department of Earth Sciences, Chiba University, Yayoi, Inage, Chiba 263, Japan)

We have developed a new deep-tow three component magnetometer whose main feature are 1) the high accuracy measurement of magnetic vector field, attitude and position, and 2) acoustic communication. Magnetometer sensors are orthogonal triaxial fluxgate type magnetometers with the range of 100,000 nT and the resolution of 1 nT. Attitude and inertial navigation sensor composes of three ring laser gyros and three single axis accelerometers, leading the angle resolution of 0.025 degrees, the heading accuracy of 0.05 degrees rms with 0.01 degree/hour rms drift rate, and the pitch and roll angle accuracy of < 0.1 degrees. The sampling rate is 5Hz. The positioning of the deep towed instrument is done using two methods. The first one is an inertial navigation which gives continuous position, but the absolute error become larger with time (about 1 km for an hour), because the position is determined by the integration of three axis accelerations and angler velocities. The second one is the combination of a GPS on board, a short base line acoustic measurement and a pressure measurement. This can give absolute position with the error of 200m in 30 second interval. The combination of the two methods could give the continuous position with better accuracy. Moreover, the acoustic communication with the rate of 60 bit/second helps to know the data quality in real time. This system is required only a winch for deep towing and would be easily used by any vessels with the winch.

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