• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.1
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• pp.13-20
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• 1991

This paper describes the fish-density dependence of the mean backscattering strength with aggregations of encaged, free-swimming fish of known density in relation to the experimental verification of echo-integration technique for estimating the density of fish shoals. In this experiment, various numbers of gold crussian, Carassius burgeri burgeri, with a mean length of 18.5cm and a mean weight of 205.9g, were introduced into a net cage of approximately 0.76m super(3). During the backscattering measurements. the cage was suspended on the sound axis of the 50kHz transducer having a beam width of 33 degrees at -3dB downpoints. The volume backscattering strengths from fish aggregations were measured as a function of fish density. Data acquisition, processing and analysis were performed by means of the microcomputer-based sonar-echo processor including a FFT analyzer. The calibration of echo-sounder system was carried out at field with a steel ball bearing of 38mm in diameter having the target strength of -40.8dB. The dorsal-aspect target strengths on anesthetized specimens of gold crussian used in the cage experiment were measured and compared with the target strength predicted by the fish density-echo energy relationship for aggregations of free-swimming gold crussian in the cage. The results obtained can be summarized as follows: 1. The target strengths in the dorsal aspect on anesthetized specimens of gold crussian, with the mean length of 19.1cm and the mean weight of 210.5g, varied from -40.9dB to -44.8dB with a mean of -42.6dB. This mean target strength did not differ significantly from that predicted by the regression of echo energy on fish density of free-swimming gold crussian in the cage. It suggests that the target-strength measurements on anesthetized fish was valid and can be representative for live, free-swimming fish. 2. The relationship between mean backscattering strength(, dB) and distribution density of gold $crussian(\rho, $ fish/m super(3)) was expressed by the following equation; =-41.9+11 $Log(\rho)$ with a correlation coefficient of 0.97. This result support the existence of a linear relationship between fish density and echo energy, but suggest that this line has steeper slope than the regression by the theory of estimating the density of fish schools.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.3
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• pp.205-213
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• 2005

A hydroacoustic and a close-open-close zooplankton net survey were conducted to understand the distribution characteristics of the deep scattering layer (DSL) and to estimate the density of zooplankton in the DSL, in the Uljin coastal area. The survey was carried out during March 13-14 and June 4-5, 2003 at each station for zooplankton. The vertical migration mechanisms of zooplankton are very variable to the taxa. In this study, after we grasp the vertical migration of zooplankton through the results of an echo-sounder survey, we verified the mechanisms of their vertical migration in the Uljin coastal area. Also, to estimate effectively the biomass of zooplankton, we researched the acoustic scattering strength according to the species. On the basis of these results, we devised a method for estimating zooplankton biomass through comparing net and echo-soundings. We obtained the results as a follows; 1) According to the examination of collections from the net sampling, in March, 2003, Euphausia pacifica comprised $38\%$ of zooplanktons inhabiting the sound scattering layer, while copepods, chaetognaths, and amphipods accounted for $29\%,\;23\%\;and\;10\%$, respectively. And in June, 2003, the ratio of E. pacifica was $51\%$, copepods $43\%$, and the others comprised $6\%$. In both March and June E. pacifica showed dominance among the species of zooplankton. 2) The analysis of vertical distribution through acoustic data in the scattering layer was more apparent in June (spring/summer) of 2003, than in March (winter/spring) of that year. The vertical migration of zooplankton peaked around sunrise and sunset in both March and June. 3) As for the sound scattering layer, it distributed in the open sea in March, and in the inland sea in June. Therefore it is suggested that some zooplankton species such as E. pacifica performed ontogenic horizontal migration througth the spring and early summer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.863-868
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• 2016

In this study, the precise shapes of sunken ships and information on seafloor topography were analyzed using data obtained from a multi-beam echo sounder. The state of each sunken ship was analyzed by processing diverse imagery data which was compared with data obtained from past investigations to determine changes in the state and circumjacent seafloor topography. Apparent changes in the seafloor topography around one sunken ship, the "Pacific Friend", were found from stern to bow as a result of continued submarine erosion and sedimentation. In the case of sunken ship "No. 7 Haeseong", the partial collapse of the bow was revealed in the seabed images captured in 2015, though it had still been intact in images captured during the Korea Hydrographic and Oceanographic Agency's investigation in 2011. This partial collapse was presumed to have resulted from the effects of continued tidal currents, the cargo load of the ship and continued corrosion of the ship over a long time on the seabed. Continuous monitoring of residual fuel inside the ship is necessary to avoid leakage and potential marine pollution. By conducting image analysis on these sunken ships, it has been determined that the structural safety of the ships is seriously influenced by tidal currents and seafloor topography, while the hulls will be continuously changed by corrosion. As a result, it can be concluded that the development of prediction and response techniques that take into consideration residual fuel leakage and environmental changes according to the geological characteristics of sunken ships is necessary.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.3
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• pp.183-190
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• 1993

A cooperative Korea-Japan investigation for the demersal fisheries resources of the East China Sea carried out by using the training ship Oshoro Maru belong to Hok-kaido University, Japan, during 1-8 November, 1991. The research vessel sampled 15 stations with demersal trawls on the East China Sea, and 1,364 nautical miles of track line were surveyed hydroacoustically. The hydroacoustic observations were taken with a scientific echo sounder operating at two frequencies of 25 kHz and 100 kHz, and a microcomputer-based echo integrator. Fish samples were collected by demersal trawling, and temperature, salinity and dissolved oxygen were measured with a CTD system. The target strength of fish school was estimated from the relationship between mean scattering strength and catches caught by demersal trawling. The results obtained can be summarized as follows: 1. The mean backscattering strength for 15 layers occupied by demersal trawls at 25 kHz ranged from -70.4 dB to -59.1 dB. Then the catch per one hour ranged from 8.2 to 587.5 kg/hour. 2. The mean backscattering strength for the entire layer between transducer and seabed in the survey area of the East China Sea at 25 kHz and 100 kHz were -68.0 dB and -73.1 dB, respectively. 3. The mean fish-school target strength per one kilogram at 25 kHz and 100 kHz were -28.3 dB/kg, and -30.4 dB/kg, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1D
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• pp.141-147
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• 2006

Soil losses are occurred by rainfall has caused productivity decline of a fertile surface soil and inflow sediment on Dam reservoir which are the main reasons of the decrease of storage volume and difficulty of water management. In this study, the amount and location of soil losses which were evaluated using USLE(Universal Soil Loss Equation) were applied on soil, landcover, and topographical conditions on the basis of satellite images and GIS. Furthermore, it was possible to evaluate the amount of riverbed sediments using echo-sounder and sediment rate were analyzed by comparing with soil losses.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.11a
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• pp.33-45
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• 2006

The interest of sediment has been increased daily because most of domestic dam reservoir's operation time have been extended and wide basin area is the main characteristics for artificial reservoir which the speed of water flow in artificial reservoir is slower than that of natural reservoir. Therefore a lot of sediment has been significantly accumulated. In this study, the accurate topographic data were obtained using echo-sounding system. GPS survey, low-frequency sub-bottom profiler, and high-frequency echo-sounding system were used to compute the exact amount of sediment. Based on the results, DEM(Digital Elevation Model) and DSM(Digital Surface Model) were generated. The GIS system for the management of sediment was created based on topographic data on the riverbed and this system can be efficiently used for the management of sediment which caused the problems of reservoir capacity and water quality.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.3
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• pp.266-272
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• 1996

The distribution and abundance of fish in the Cheju southeastern area was studied by the combined hydroacoustic and bottom trawl surveys in April 1994 and in July 1995, respectively. The main purpose of these investigations was to provide the basic data for this management and the biomass estimation of commercially important demersal fish stocks in this area. The hydroacoustic surveys were performed by using a 50 kHz scientific echo sounder system with a microcomputer-based echo integrator. Acoustical measurements of fish abundance and distribution were conducted along the cruise tracks of research vessel and during all trawl hauls by continuous echo sounding. The average weight-normalized target strength for demersal fish aggregations was derived from the relationship between the mean volume backscattering strength for the depth strata of trawl hauls and the weight per cubic meter of trawl catches. The geographical distribution of fish stocks in the 1994 survey area was investigated in relation to oceanographic conditions. The results obtained can be summarized as follows: 1. From the 1994 and 1995 survey data, the relationship between the mean volume backscattering strength (, dB) for the depth strata of trawl hauls and the weight (W, kg/$m^3$) per cubic meter of trawl catches was expressed by the following equation = - 32.8+ lOlog(W) The average weighted-target strength value at 50 kHz derived from this equation was .. 32.8 dB/kg. 2. In 1994 and 1995, both surveys showed a trend of decreasing fish abundance toward the southern area of the Cheju Island with high densities offish along the west coast ofth.e Tsushima Island. The highest demersal concentrations in the southern area of the CheJu Island appeared in bottom waters colder than $12^{\circ}C.$. . 3. From the results of combined bottom trawl and hydroacoustic surveys, the estunated fish densities in the southeastern area of the Cheju Island were 1.5488 x $10^-4$kg/$m^3$ in the 1994 surveyand 1.9498 x $10^-4$kg/$m^3$ in the 1995 survey, respectively.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.38-46
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• 1996

In this paper, a multi-velocity log system which uses ultrasonic pulsed doppler signal is developed. The output of the system is the absoluted velcocity of the ship. By using digitral signal processing, we get the vector velocity which displays the ship's speed about fore, aft, port and starboard. And this system give us the information about depth. This multi-velocity system has a large merit that is bottom and water track velocity. In addition, this has the high accuracy and can measure the water-depth according to the deep mode. And the fish finder, echo sounder or docking system will be made by applying the speed log system.

• Journal of the Korean Institute of Navigation
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• v.3 no.2
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• pp.21-30
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• 1979

Echo sounder and Doppler sonar are to theultra-sonic transducers for measuring the depth and the ship's speed respectively. To measure the depth and speed with a single transducer, it is required to control the ultra-sonic beam to optional direction. In the past, the direction of the transducer itself is varied, but such a method provoked much problems in the mechanical design of the equipment. This paper deals with the method to control beam direciton by the phase control of the plural arrangement of transducers, and the results are studied by a computer simulation. The remarkable results of the study is condensed as follows; 1. The greater the interval of arrangement between transducers, the sharper the radiation pattern is, but in this case, the level of undesired sidelobe is also increased. 2. The control of radiation pattern up to 60 degree can be achieved by an adequate arrangement of more than 10 transducers. 3. It is shown that a simultaneous measurement of both depth and speed can be achieved by alternating directivity of the pulse by the method proposed in this paper.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.774-781
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• 2013

The purpose of this paper is to design a DVL-RPM based VKF (Velocity Kalman Filter) design for a performance improvement underwater integrated navigation system. The proposed approach relies on a VKF, augmented by a altitude from Echo-sounder based switching architecture to yield robust performance, even when DVL (Doppler Velocity Log) exceeds the measurement range and the measured value is unable to be valid. The proposed approach relies on two parts: 1) Indirect feedback navigation Kalman filter design, 2) VKF design. To evaluate proposed method, we compare the results of the VKF aided navigation system with simulation result from a PINS (Pure Inertial Navigation System) and conventional INS-DVL method. Simulations illustrate the effectiveness of the underwater navigation system assisted by the additional DVL-RPM based VKF in underwater environment.