We have made possible a compilation of the exact constant currents by separating tidal currents from sea currents. Then, sea current data should be corrected for an elimination of measurement errors in ADCP data based on direction change or pitch and roll in navigation of a survey vessel. This correction method has been developed by one of the authors.
In this paper, the results of our application for the East China Sea are shown by the original current pattern of the Tsushima warm current and the Yellow Sea warm current. Moreover, we consider it is clarified that the cold anticlockwised eddy exsists at northern part in the vicinity of the Kuroshio turning point in the same Sea. Justly, both NOAA-AVHRR imagery and Argos bouy data support these results.

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Because of the remarkable progression of video imagery technology, it seems that the recent applications of video imageries to many branches of terrestrial survey have surpassed the status of photographic images.
Especially, our video camera mounted on gyro-stabilized system out of helicopter provides the high-quality imageries to us.
In this paper, outline of our applications to investigation for sea cliff on the coastal line and for coastal waves and currents.

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Hydrographic Department is to start the GPS observations on crustal deformation around Sagami Bay from the beginning of 1990. Here we report the results of test observations which were carried out at O Sima. Manazuru and Izu Sirahama in March and July (just after the occurrence of volcanic activity at Teisi knoll on July 13), in 1989. Phase differences of two carrier frequencies were measured, and it was found that if 4 GPS satellites are visible and 6 hours' observation is secured then we can obtain good repeatability of 1 ppm or less.

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Capability of the swell-compensator for Nos. 1 and 2 winches on the Hakuho-Maru has been evaluated by a deep-sea pressure sensor. This swell-compensator has two modes: i) active mode which can compensate the ship movement detected by the accelerometer close to the gantries, ii) passive mode controlling the wire tension smoothly from accidental snatch tensions. Heaving displacement of the end of winch wire during active mode operation of the swell-compensator decreases to one-third to one-fifth of that of no control mode. Heaving displacement of wire end of at least 0.3 to 1.0 meter still remains depending on wire length, even if swell-compensator is operated in active mode. Passive mode seems to be useful only for deduction of accidental tension load on the winch and gantry.

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A submarine volcano "Teisi Knoll " erupted in the western part of Sagami Bay, east of Izu Peninsula on July 13, 1989. Coincidentally, S/V "TAKUYO" of the Hydrographic Department of Japan was engaged in the survey in the area which was hit by a swarm of earthquake having become active since June 30, 1989, and encountered the eruption within the distance of 500 meters. We recorded the volcanic eruption by means of VTR, camera and tape recorders. The HD carried out seabottom surveys 3 times in total before and after the eruption, and has observed topographic change of sea bed birth of a submarine volcano. On July 9, S/V "MEIYO" observed flat sea floor 100 meters deep. While in the morning of July 13 S/V "TAKUYO" observed a cone-shaped height of 25 meters elevation on the floor. On July 15, S/V "SHOYO" observed Teisi Knoll with a crater ranging 200 meters in diameter by means of a radio controlled buoy "MANBOU"

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On this paper, we describe the result in a basic study for a technical developing classification of coastal bottom material by using of acoustic reflection method. As the item of classification of bottom material, we selected, especially, such physical properties as grain size distribution and volume concentration (porosity) of particles in soft-mudsediment. Newly physical parameter CPC (cumulative weight percentage of particle volume concentration) is defined.
The other hand, we have derived a new conception of acoustic propagation, sound velocity and attenuation, for a model of N-phase suspension. In the conception, the volume ratio of N-phase particles classified by grain size in modefied suspension is particularly introduced.
The applicability of the conception for the soft-mud sediment was verified through both numerical simulations and laboratory experiments measuring physical properties, sound speed and attenuation at several frequencies.
A center frequency f of sound speed dispersion has a good response with the mediam grain size φ_m (φ_m=-log₂ 2 a_m; a_m is radius of particle in milli-meter) in the CPC curve. Then, the regressive formulation is
φ_m=1.62 F+3.99±0.244
where F≡log₁₀ f; f in kHz.
A maximum V_m of sound velocity at higher frequency range, eg. several hunderd kilo-hertz to several hundred mega-hertz, etc., is corresponding to the maximum of CPC curve at each volume concentration C_p. The theoretical formulation is
C_p=CPC={1.125 (V_m-1)}^1/2
where V_m=|V_s/V_l|_max.
By using these formulas, φ_m and C_p can be predicted from measured F and V_m.

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We tested the marine environmental moniroring system off west coast of Hokkaido in Japan Sea from 1986 to 1988.
The system consists of marine observation buoy, land weather observatory, data receiving station, data management station and terminals.
Marine observation buoy forms 11 sensors for each layer in the different depth of the water. And, data management station has contoroller of data receiving and a function as the host station on personal computer communication.
This station transmits the observed data by access through the public telephone networks from each terminal.
We moored the observation buoy by using several rings for prevention of twistig.
Therefore, the buoy was able to endure waves of 5 meters high by using these rings.

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