• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.2
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• pp.154-163
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• 2015

This study is based on deductions from analysis of historical changes in hydrographic surveys, the problems with the existing system in Korea and analysis of the literature, including foreign cases. Using these criteria, we created and administered a survey of marine professionals of Korea, and based on the results, established an order of priority for hydrographic surveys, as follows: changes in the seabed, quantities of marine traffic, existing performance data from hydrographic survey, consumer's demand, marine accidents, conservation of oceanic environment, and natural resources. The study also deduced, based on a survey of experts, the relative importance ranking of the major ports in South Korea and suggests policy implications and a priority decision model to conduct future hydrographic surveys in a more scientific and systematic way.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.211-221
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• 2017

Ellipsodially referenced survey (ERS) is considered as one of the challenging issues in the hydrographic surveys due to the fact that the bathymetric data collected by this technique can be readily transformed either to the geodetic or the chart datum by application of some geoscientific models. Global Navigation Satellite Systems (GNSS) is a preferred technique to determine the ellipsoidal height of a vessel reference point (RP) because it provides cost-effective and unprecedentedly accurate positioning solutions. Especially, the GNSS-derived heights include heave and dynamic draft of a vessel, so as for the reduced bathymetric solutions to be potentially free from these corrections. Although over the last few decades, differential GNSS (DGNSS) has been widely adopted in the bathymetric surveys, it only provides limited accuracy of the vertical component. This technical barrier can be effectively overcome by adopting the so-called GNSS carrier phase (CPH) based techniques, enhancing accuracy of the height solution up to few centimeters. From the positioning algorithm standpoint, the CPH-based techniques are categorized under absolute and relative positioning in post-processing mode; the former is precise point positioning (PPP) correcting errors by the global or regional models, the latter is post-processed kinematic positioning (PPK) that uses the differencing technique to common error sources between two receivers. This study has focused on assessment of achievable accuracy of the ellipsoidal heights obtained from these CPH-based techniques with a view to their applications to hydrographic surveys where project area is, especially, few tens to hundreds kilometers away from the shore. Some field trials have been designed and performed so as to collect GNSS observables on static and kinematic mode. In this paper, details of these tests and processed results are presented and discussed.

• Ocean and Polar Research
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• v.28 no.3
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• pp.259-272
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• 2006

The 1982 UNCLOS provided very detailed provisions on marine scientific research and gave coastal stale jurisdiction to regulate marine scientific research in its EEZ. However, due to lack of definition and criteria of MSR, there are some different views, even conflicts, regarding legal Pounds for governing hydrographic surveys and oceanographic data collection by one state in the EEZs of other states. Some coastal states argue that those activities should only be conducted in the EEZ of other states with the consent of the coastal state while it is the opinion of other states, including the U.S.A., that those activities can be conducted freely in the EEZ. This paper reviews different views and recent developments on the issue and suggests some recommendations for future work of the Korean government related to the activities.

• 한국해양학회지
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• v.17 no.2
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• pp.59-68
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• 1982

Vertically homogeneous water was found around the convex coast of Jeju Island on its west side from hydrographic surveys conducted in June and Ictober 1980, and June 1981. This is the first time that this hydrographic structure is observed. Historical data do not show this water, since they wewe taken far from the island. The presence of this homogeneous water is explained in terms of tidal mexing for the lower half of the water column and relling for the upper half of the columa which conserve vorticity as currints flow clockwise around the island. Direct measurement in future is required to prove the upwelling mechanism.

• Ocean Science Journal
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• v.41 no.4
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• pp.291-299
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• 2006

Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in June and November 2004. The bottom cold water, which was lower than $10^{\circ}C$, appeared in the channel trough except in March 2003. It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed of the intrusion current were about 20 km and approximately $25\;cm\;s^{-1}$, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv ($Sv{\equiv}10^6\;m^3\;s^{-1}$) in August 2003 and 0.026 Sv in November 2004.

• Ocean and Polar Research
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• v.27 no.2
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• pp.183-188
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• 2005

Using data from Argo floats collected in the Southern Ocean, we describe water mass prop erties and flow fields at intermediate levels (1000m and 2000m levels). Water mass properties from Argo floats, which are consistent with those from previous hydrographic surveys, reflect the movement of the floats well even without quality control on the Argo data. Since the flow fields from the Argo floats do not cover the entire Southern Ocean, we could not obtain a general circulation pattern, especially at the 2000m level. We, however, can confirm the general eastward tendency due to ACC largely following the topography.

• Journal of the Korean earth science society
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• v.26 no.8
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• pp.836-843
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• 2005

Two data sets of repeated hydrographic surveys with a single beam echo-sounder were obtained to investigate morphological changes on a sand mining site within EEZ near the Eocheong Islands, West Sea of Korea. Their accuracies of depth measurement, estimated from the crossover analysis, correspond to the Oder 2 of IHO standards. Bathymetric maps show a feature of 300m wide and 10m deep hollow, whose evolution can be seen in difference grids of the two bathymetric maps. However, data of higher accuracy and resolution enable precise quantification of extracted sand volume. Since this morphological change could affect sedimentary environment as well as benthic ecology, environmental impact assessment based on scientific research data is required for management and sustainable development of limited sand resource.

• 한국해양학회지
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• v.26 no.3
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• pp.262-277
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• 1991

Hydrographic data taken at stations spaced 8-16 nautical miles in the Cheju Strait and the southeastern part of the Yellow Sea in June 1980 and August 1981 show for the first time that oceanic water of high temperature and high salinity exists within 20 km from the northern and western coast of Cheju-Do. It is confirmed that the low salinity trough in the sea around Cheju-Do originates from the river plume on the Yantze Bank. The salinity trough separates the high temperature and high salinity water around Cheju-Do from the surface water of the Yellow Sea and below the seasonal thermocline this distance water meets the Yellow Sea Cold Water forming a thermal front. The Yellow Sea Cold Water seems to spread southward along the Yantze Bank centered at the isobath of 70 m. Its characteristics also appear in the northern part of the Cheju Strait. these complex structures contradict the yellow Sea Warm current suggested by Uda 1934), which is supposed to flow northward into the Yellow Sea along the western coast of Korea. Our data show that dense hydrographic surveys in space and time are prerequisite to understand the circulation around Cheju-Do.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.663-663
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• 2002

The National Oceanographic Research Institute of KOREA started to survey for the basic data necessary to territorial sea and EEZ identification and marine development with Multi-Beam Echo Sounder(L3 SeaBeam 2112) since 1996. The Multi-Beam surveys has provided a very new and precise way of describing the morphology and nature of the underwater seabed. Multi-Beam Echo Sounder systems employ sound waves propagating at angles which vary from vertical to nearly horizontal. The locations on the bottom where echoes are generated cover a swath whose port to starboard width may be equal to many times the water depth. Newer Multi-beam bathymetric sonars provide both a beam by beam depth and backscatter amplitude of the bottom. But The backscattered amplitude didn't use for identification of bottom properties because backscatter amplitude effects by the many environmental variables of underwater and seabed. We investigates the utilization of geo-referenced backscatter amplitude and analysis of relationship between The Backscattered Amplitude and Sidescan Sonar imagery from Sea Beam 2112. For the backscattered amplitude imagery mainly represents the properties of sediment, we computed the beam geometry, time-varied amplifier gain, and mainly incidence angle to the topography using bathymetric model at each ping. In this paper, those issues are illustrated, and the angular independent imagery based on swath topographic model is described.

• Ocean and Polar Research
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• v.23 no.2
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• pp.195-203
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• 2001

A fine-grid (3 km ${\times}$ 3 km), three-dimensional nowcast system of sea levels, currents, temperature, and salinity is being developed for the Taiwan Strait. The project takes a balanced approach relying equally on models and observations, will have the capacity of real-time data assimilation, and is aimed at both practical and scientific applications. To determine boundary conditions and verify model results, eight coastal tide-gauge stations were first established along both sides of the strait. Strait-wide hydrographic surveys were conducted by research vessels. Currents are being measured using bottom-mounted ADCP moorings in a meridional deep channel off southwest Taiwan and along a traverse section in the central part of the strait. In addition to a fine-resolution three-dimensional model of the Taiwan Strait, an adjoint model and a larger-domain two-dimensional model were used to better determine boundary conditions in the northern and southern boundaries of the strait. In the first stage of model development, barotropic tides were successfully simulated in a hindcast mode. The protocol product has been released to general public, including government agencies, universities and general users.