A real-time onboard data collection and distribution system was developed for the new R/V Hakuho-Maru of the Ocean Research Institute, University of Tokyo. The system is controlled by the Magnavox Series 5000 integrated navigation system (MX5000). MX5000 implements collection and storage of data from ship positioning sensors and research equipments, accurate ship position determination with Kalman filtering, and distribution of navigation and research data. Most of the data link necessary for the real-time data processing is carried out through the optical local area network (LAN). Data distributed in each laboratory can be obtained by RS-232C serial interface. They are displayed at a monitor in each laboratory. Optical LAN also supports data link to be able to communicate between laboratories.
Recently, the requirements for accurate positioning for various scientific investigations in the ocean areas are on the increase. At the present time, one of the most effective positioning system to meet these requirements is an application of ocean bottom control network being consist of three or more acoustic transponders. In a previous report (Yamazaki, 1975), the writer proposed a new technique which determine the geometry on the three transponder network positioning and estimated the accuracy of its solution. There we implicitly assumed that the simultaneous acoustic range measurements are performed from stopped ship. However, it is technically difficult and non-efficient to stop ship at each time. So this time, considering practical use, the accuracy of the three transponder geometry in the case of measurements from sailing ship are reestimated by the simulation methods using personal computer. Based on some assumptions,the results obtained show that the accuracy is estimated as about 10cm for ranging accuracy of 10-3 at 3,000m base line of transponder network. Furthermore, the use of this technique in conjunction with GPS will make it possible to determine the geodetic positions of transponders with the accuracy of about 0.04" for GPS accuracy of 10m.
In 1984 a research group was organized in the Institute of Industrial Science, the University of Tokyo to study the next-decade technology for underwater robotics in the deep sea. In 1986 this group was re-organized and 'PTEROA Project' was started to develop cruising type robots for the survey of deep-sea floors. The project was funded by the Ministry of Education and Science of Japan. The mission of PTEROA robot is to carry out specified measurement, for example, measurement of CTDO and taking pictures of the bed, during cruising over the bed. In the first/last stage of the mission, the vehicle glides from/to the surface to/from a target point. If it dives to 6000 m depth at gliding angle of 15 deg, it could cover an area 22 km radius from the mother ship. At the bottom, the vehicle is obliged to keep constant altitude from the bed. On the basis of ranging data provided by four ranging sonars of 150 kHz to measure the configuration of the bed, the vehicle should determine the direction to which it should swim. A pilot-model vehicle named PTEROA 150 has been constructed in 1989, which can dive to 2000 m depth and cruise for 1 hour in 2 knots. Length, width and height of the body are 150 cm, 75 cm and 45 cm, respectively. Dry weight is 220 kg. Two oil-immersed thrusters of 300 W are fitted at aft. Three actuators to trim control surfaces, i. e. a pair of elevators and a rudder, were constructed with oil-immersed stepping motors. On the basis of the knowledge and experience through the development of PTEROA 150, a prototype vehicle PTEROA 250 was designed, which is anticipated to dive to 6000 m depth and to cruise above the bed in 4 knots for 2 hours.
Hydrographic Department, Maritime Safety Agency conducted multi-channel seismic reflection survey around the junction of Izu-Ogasawara trench and the Sagami trough. Three plates, the Pacific plate, the Philippine Sea plate and the northeast Japan plate contact each other at the junction. Seismic profiles show that the Philippine Sea plate subducts beneath the northeast Japan plate. Moreover, the Pacific plate is recognized bellow the subdudted Philippine Sea plate. The subducted Philippine Sea plate trends north east and dips north with deformation. The eastern end of the Philippine Sea plate crops out at the east of Taito spur. This fact is concluded that the contact point of the three plates is located at the northern margin of the Bando deep sea basin.
For easy interpretation of total magnetic anomaly profiles, personal computer software has been developed. In this software, curve fitting method is used in solving non-linear equations of parameters of a source body model. Two types of source models are adopted: an infinite vertical prism model with four parameters and a finite dipping prism model with five parameters. The former model can be applied to the case when the top surface is not flat, whereas the latter can be used in the case when the prism is not vertical and the bottom is in a finite depth. The developed curve fitting method was successfully applied to profile data: results were obtained after about ten iterations or less. However, when the bottom depth was included in the unknown model parameters, number of iterations increased, and unexpected results are occasionally obtained. Three acceptable types of input data are: magnetic profile data, data obtained by digitizing a magnetic map, and data interpolated from gridded magnetic data. Preparation of the profile data and input of initial guess parameters are interactively executed by checking the profile display.
This paper presents a new method to analize magnetic and gravity anomalies in a comprehensive manner using a response function between magnetic and gravity anomaly. The response function of a linear system, whose input is magnetic anomaly and output is gravity anomaly, is newly defined by a Fourier transform of the gravity anomaly divided by that of magnetic anomaly. Response function of two-dimensional magnetic and gravity anomalies contains two informations concerning with a source body. The phase factor (δ) of the response function can be related with effective inclinations of magnetic field and magnetization vector as, δ=Io'+Ir'-π, where Io' is an effective inclination of magnetic field and Ir' is an effective inclination of magnetization vector. Besides, the amplitude term of response function gives the density/magnetic moment ratio of the source body. This method was applied to the profiles of aero-magnetic and Bouguer gravity anomaly of Tohoku Japan. A basic formula of three-dimensional response function is also indicated in this paper.