• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.83-88
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• 2001

In this paper, matched field processing algorithm robust to environmental mismatches in an ocean waveguide based on feature extraction is summarized. However, in applying this processor to localize a source there are two preliminary issues to be resolved. One is the number of eigenvectors to be extracted and the other is the number of environmental samples to be used. To determine these issues, the relation between the number of dominant modes propagating in a given ocean waveguide and that of eigenvectors to be extracted is analyzed. Then, the analysis results are confirmed by the subspace analysis. This analysis quantifies the similarity between the subspace spanned by the signal vectors and that spanned by the eigenvectors to be extracted. The error index is defined as a relative difference between the location estimated by the current processor and the real source location. It is identified that in the case of extracting the largest eigenvectors equal to the number of dominant modes in a given environment, the processor localizes the source successfully. From the numerical simulations, it is shown that use of at least 30 environmental samples guarantee stable performance of the proposed processor.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.185-190
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• 2011

In marine controlled-source electromagnetic (CSEM) modeling, it may be difficult to evaluate primary fields accurately using conventional linear filters because they decay very rapidly with distance. However, since there exists a closed-form solution to the Hankel transform in TM mode for a homogeneous half space, we can assess the accuracy of linear filters for evaluating the Hankel transform. As a result, only nine out of 36 source-receiver pairs show that EM fields decrease linearly in semi-log scale with an increase of source-receiver distance, while EM fields are either 0 or not reduced significantly due to an effect of the air layer. There also exist closed-form solutions for the nine pairs, and the others can be evaluated accurately with a relatively short filter. This paper proposes a method which uses closed-form solutions for TM-mode Hankel transforms and a filter with 61 coefficients for TE-mode ones.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.15-20
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• 2003

한국항공우주연구원은 공공기술연구회 산하 한국지질자원연구원, 한국해양연구원, 한국건설기술연구원과 협력하여 2002년 4월 17일에 본격적인 원격탐사 연구 및 공공지원 업무의 주축을 담당하게 될 공공원격탐사센터를 설립하였다. 별도의 독립조직이 아니라 원격탐사위성인 아리랑위성을 개발, 운영하고 있는 한국항공우주연구원을 중심으로, 한국해양연구원, 한국지질자원연구원, 한국건설기술연구원등 관련기관이 해양분야, 지상분야, 건설분야 등 각 전문분야 별로 협동연구 체계를 구축, 실질적인 국가원격탐사센터 역할을 수행할 것이다. 이와 같이 설립된 공공원격탐사센터에 대한 홍보, 위성자료의 공공활용 지원 및 원격탐사 Tutorial 등을 사용자들이 쉽게 접속하여 이용할 수 있도록 공공원격탐사센터 홈페이지를 구축하여 Open 하게 되었다. 공공원격탐사센터 본부인 한국항공우주연구원을 비롯하여 전문센터별로도 홈페이지를 구축하여 서로 연결되도록 하였다. 2003년도에는 이와 같이 open 된 홈페이지에 위성자료 통합 DB를 구축하여 서비스할 예정이다.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.313-321
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• 2003

우리나라의 연간 물동량 중 선박에 의한 물동량이 약 90% 이상을 차지하고 있으나 이러한 선박에 의한 막대한 물동량을 효율적으로 처리하기 위한 해양물류시스템의 구축이 미진한 상태이다. 이를 위해 국가에서는 항만의 물류시설을 확충하는 등 물리적인 대안을 가지고 시설 부족에 대한 대비를 하고 있다. 그러나 해양물류시스템에 있어서 또 다른 중요한 문제점은 각 선사별, 물류회사별로 공통업무에 대해 각기 다른 시스템과 데이터베이스를 운영함에 있다는 것이다. 이와 같은 독립적 시스템의 운영은 동일 업무에 대한 중복투자를 유발하게 되어 많은 시간 및 비용을 소요하게 되며, 원활한 정보교환에 걸림돌이 되고 있다. 따라서 본 연구에서는 국제적인 표준안이 마련되어 있는 전자해도(ENC, Electronic Nautical Chart)를 이용하여 클라이언트-서버 방식의 관리자용 선박 및 화물 위치검색시스템을 구현하였으며, 추후 다른 항만에서도 사용이 가능하여 독립적 시스템의 운영으로 인한 중복투자를 방지 할 수 있는 방안을 제시하였다. 아울러 전자해도의 새로운 활용 방안이 없는 현 시점에서 전자해도를 선박 및 화물 위치검색시스템의 위치 표시를 위한 도형 데이터베이스로 사용하여 전자해도 본연의 목적 이외에도 활용될 수 있는 실례를 제시함으로써 전자해도의 새로운 활용 가능성을 제시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.142-146
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• 2017

지진해일의 수리특성을 분석하기 위하여 유사한 파형특성을 가진 고립파를 많이 이용하고 있다. 그러나 고립파의 근사파형은 실제 지진해일에 비해 상당히 좁은 파형분포를 가지고 있다. 이에 수치모의에서는 기존의 고립파 근사식을 개량하여 고립파형의 지진해일을 수치적으로 생성하고 있다. 본 연구에서는 지진해일의 파형분포에 따른 월파특성을 수치적으로 조사하기 위하여 개량된 고립파 근사식을 2차원 N-S solver에서 적용하였다. 이것에 기초하여 수치파동수조에 직립호안과 그 배후에는 월파수조를 설치하고, 지진해일 월파량을 측정하였다. 수치해석결과로부터 직립호안 주변의 공간파형과 마루 위의 유속분포로부터 파형분포에 따른 월파현상을 분석할 수 있었다. 또한 기존 고립파 근사이론 대비 개량된 고립파의 체적비에 따른 월파량 변화를 정량적으로 조사하였다. 그 결과 지진해일의 체적비가 증가할수록 월파량이 거의 선형적으로 증가하는 경향을 나타내었다.

• Journal of Internet Computing and Services
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• v.1 no.1
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• pp.73-86
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• 2000

The Geographic Information System (GIS) is a system that collects, stores, analyzes and processes geographic object data existing in space. The GIS is widely used in application fields related to geography such as city planning, land-register management, forest resources management, etc. The importance and necessity of the GIS have been well demonstrated, and therefore many studies on this system have been carried out. However, most of those studies have just treated geographic information as spatial information, but have not considered or have overlooked changes of spatial data dependent on time. For example, transportation information management and atmospheric phenomena forecast, have not exactly reflected the actual world which changes with the flow of time. In this thesis, a temporal GIS is established to effectively and precisely process information on space objects changing with time and a database is built up in reference to changes in water temperature and salinity. And the isotherm and isohaline forecast system implemented to support graphical tool.

• Spatial Information Research
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• v.21 no.4
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• pp.71-81
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• 2013

Due to explosively increasing utilization in spatial information and a rapid development in geospatial technology related to national territorial and housing, there are increasing demands for converging spatial information on not only urban planning and real estate data but also newly generated data from smart phone, GPS to achieve comparative advantage of national territory. In this paper, we prospect the utilization of Converged Spatial Information(CSI) to future national territorial planning for the purpose of enhancing territorial competitiveness. For this purpose, considering the Korea Land and Housing corporation(LH) takes charge most of government's land and housing development projects, CSI usage of this company's 6 future business domains until 2029 were used as a case study. Also, 7 CSIs derived from literature review were surveyed to find the degree of CSI utilization in the national territorial future. In the analysis result, it was found that 3D data and mobile data among others have higher degree of utilization, and urban and regional development is the most highly utilizable domain for CSIs. After all, to revitalize the use of CSI in national territorial future, it is required to do a balanced construction of territorial use spatial information about marine use, coastal use, underground space besides land use.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1120-1128
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• 2022

In the event of a marine accident, the longer the exposure time to the sea increases, the faster the chance of survival decreases. However, because the search area of the sea is extremely wide compared to that of land, marine object detection technology based on the sensor mounted on a satellite or an aircraft must be applied rather than ship for an efficient search. The purpose of this study was to rapidly detect an object in the ocean using a hyperspectral image sensor mounted on an aircraft. The image captured by this sensor has a spatial resolution of 8,241 × 1,024, and is a large-capacity data comprising 127 spectra and a resolution of 0.7 m per pixel. In this study, a marine object detection model was developed that combines a seawater identification algorithm using DBSCAN and a density-based land removal algorithm to rapidly analyze large data. When the developed detection model was applied to the hyperspectral image, the performance of analyzing a sea area of about 5 km² within 100 s was confirmed. In addition, to evaluate the detection accuracy of the developed model, hyperspectral images of the Mokpo, Gunsan, and Yeosu regions were taken using an aircraft. As a result, ships in the experimental image could be detected with an accuracy of 90 %. The technology developed in this study is expected to be utilized as important information to support the search and rescue activities of small ships and human life.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.2
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• pp.96-106
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• 2000

Though the recent years, large scale structures have been built on offshore for utilization of coastal ocean space as offshore airport and marine terminals. Sometimes, those big scale structures, however, happened to act as significant barriers against waves and severe beach erosion would take place on the coast. The present study deals nearshore topography changes affected by construction of an offshore structure with different distance from the shore. The series of three dimensional movable bed experiments have been examined in detail. Moreover, in order to make clear the relation of nearshore currents and local erosions behind offshore structure, the nearshore currents are calculated by Boussinesq equation model and compared with the same scale condition of the physical model experiments.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.239-245
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• 2006

Time-reversal processing (TRP) has been shown as an effective way to focus in both time and space. The temporal focusing properties have been used extensively in underwater acoustics communications. Recently. adaptive time-reversal processing (ATRP) was applied to the simultaneous multiple focusing in an ocean waveguide. In this study. multiple focusing with ATRP is extended to the underwater acoustic communication algorithm for multiple receiving locations. The developed algorithm is applied to the underwater acoustic communication to show, via simulation and real data, that the simultaneous self-equalization at multiple receiving locations is achieved.