• 한국인터넷방송통신학회논문지
• /
• 제12권6호
• /
• pp.189-197
• /
• 2012

본 논문에서는 위성과 모바일기기 간의 전파수신감도를 활용한 최적경로탐색 알고리즘을 제안한다. 일반적인 경로탐색은 최단경로를 기반으로 하기 때문에 위성을 이용하는 모바일기기의 안정적인 멀티미디어 서비스 제공이 어렵다. 제안된 알고리즘은 전파수신감도를 기반으로 하는 경로탐색을 통해 안정적인 통신환경의 제공을 목적으로 한다. 위성통신에서 수신환경에 따라 전파수신감도 변화가 심하기 때문에 수신환경의 특성을 정확하게 분석하는 것이 매우 중요하다. 전파감쇠 요인으로 대기감쇠, 수풀감쇠, 건물에 의한 감쇠 등을 적용하여 시뮬레이션을 통해 분석하고 전파수신감도로 활용한다. 제안된 알고리즘은 도심지에서 위성을 활용한 안정적인 멀티미디어 서비스 제공을 위한 최적경로를 찾을 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제11권1호
• /
• pp.202-210
• /
• 2019

The obstacles modeling is a fundamental and significant issue for path planning and automatic navigation of Unmanned Surface Vehicle (USV). In this study, we propose a novel obstacles modeling method based on high resolution satellite images. It involves two main steps: extraction of obstacle features and construction of convex hulls. To extract the obstacle features, a series of operations such as sea-land segmentation, obstacles details enhancement, and morphological transformations are applied. Furthermore, an efficient algorithm is proposed to mask the obstacles into convex hulls, which mainly includes the cluster analysis of obstacles area and the determination rules of edge points. Experimental results demonstrate that the models achieved by the proposed method and the manual have high similarity. As an application, the model is used to find the optimal path for USV. The study shows that the obstacles modeling method is feasible, and it can be applied to USV path planning.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
• /
• pp.409-412
• /
• 2006

Today's commercial high resolution satellite imagery such as IKONOS and QuickBird, offers the potential to extract useful spatial information for geographical database construction and GIS applications. Recognizing this potential use of high resolution satellite imagery, KARI is performing a project for developing Korea multipurpose satellite 3(KOMPSAT-3). Therefore, it is necessary to develop techniques for various GIS applications of KOMPSAT-3, using similar high resolution satellite imagery. As fundamental studies for this purpose, we focused on the extraction of 3D spatial information and the update of existing GIS data from QuickBird imagery. This paper examines the scheme for rectification of high resolution image, and suggests the convenient semi-automatic algorithm for extraction of 3D building information from a single image. The algorithm is based on triangular vector structure that consists of a building bottom point, its corresponding roof point and a shadow end point. The proposed method could increase the number of measurable building, and enhance the digitizing accuracy and the computation efficiency.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
• /
• pp.505-510
• /
• 2006

SVLBI (Space Very Long Baseline Interferometry) has some important potential applications in geodesy and geodynamics, for which one of the most difficult tasks is to precisely determine the orbit of SVLBI satellite. This paper studies several technologies which possibly will be able to determine the orbit of space VLBI satellite. And then, according to the sorts and characteristicsof satellite and the requirements for geodetic study and the geometry of GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of SVLBI satellite (TEST-SVLBI) are determined. A program is designed to analyze the coverage area of the space of different heights by the stations of the network, with which the tracking network of TEST-SVLBI is designed. The efficiency of tracking TEST-SVLBI by the network is studied, and the results are presented.

• 한국통신학회논문지
• /
• 제39C권7호
• /
• pp.515-520
• /
• 2014

본 논문에서는 기존의 해양 위성 방송 통신을 위해 사용되어온 2세대 위성 디지털 방송 표준 (Digital Video Broadcasting Satellite Second Generation : DVB-S2) 의 저밀도 패리티 검사 (Low Density Parity Check : LDPC) 부호 성능 개선과 부호화 및 복호화 복잡도를 줄일 수 있는 프로토그래프 (protograph) 기반 블록 저밀도 패리티 검사 부호를 제안한다. 모의 실험을 통하여 기존의 DVB-S2의 저밀도 패리티 검사 부호 대비 우수한 비트 오류확률 및 프레임오류확률 성능을 갖는 것을 보이며, 또한 부호화 및 복호화 계산 복잡도 분석 및 비교를 통하여 제안하는 부호가 효율적인 부호화 및 복호화 구조를 가짐을 보인다.

• International Journal of Aeronautical and Space Sciences
• /
• 제17권4호
• /
• pp.622-630
• /
• 2016

In the operation of a low earth orbit satellite, a series of antenna commands are transmitted from a ground station to the satellite within a visibility window (i.e., the time period for which an antenna of the satellite is visible from the station) and executed to control the antenna. The window is a limited resource where all data transmission is carried out. Therefore, minimizing the transmission time for the antenna commands by reducing the data size is necessary in order to provide more time for the transmission of other data. In this paper, we propose a geometric compression method based on B-spline curve fitting using dominant points in order to compactly represent the antenna commands. We transform the problem of command size reduction into a geometric problem that is relatively easier to deal with. The command data are interpreted as points in a 2D space. The geometric properties of the data distribution are considered to determine the optimal parameters for a curve approximating the data with sufficient accuracy. Experimental results demonstrate that the proposed method is superior to conventional methods currently used in practice.

• 한국위성정보통신학회논문지
• /
• 제2권2호
• /
• pp.1-9
• /
• 2007

본 논문은 고속철도 채널환경에서의 위성을 통한 Satellite Wibro 시스템의 성능열화특성과 이에 따른 보상기법에 대해 서술하였다. 고속철도 채널환경은 LOS채널 과 터널환경으로 구분되고 LOS 환경에서는 고속철도 파워 급전선에 의한 신호블로킹에 의한 문제와 터널내 에서는 Optic Fiber내에서와 같은 다중경로 간섭문제가 발생한다. 이러한 전형적인 두 채널 공간에서의 위성 와이브로 시스템 성능열화 특성을 해석적으로 규명하고 컴퓨터 시뮬레이션을 통하여 확인 하였다. 아울러 300 km/h 이상으로 이동하는 고속철도에서 발생되는 OFDM 시스템의 도플러 효과에 의한 ICI 현상과 이를 보상할 수 있는 기법을 해석적, 실험적 결과를 통하여 증명하였다.

• 대한원격탐사학회지
• /
• 제38권4호
• /
• pp.355-364
• /
• 2022

In this study a tendency of abnormal sea surface temperature (SST) occurrence in the seas around South Korea is analyzed from daily SST data from satellite and 14 buoys from August 2020 to July 2021. As thresholds 28℃ and 4℃ are used to determine marine heatwaves(MHWs) and abnormal low water temperature (ALWT), respectively, because those values are adopted by the National Institute of Fisheries Science for the breaking news of abnormal temperature. In order to calculate frequency of abnormal SST occurrence spatially by using satellite SST, research area was divided into six areas of coast and three open seas. ALWT dominantly appeared over a wide area (7,745 km²) in Gyeonggi Bay for total 94 days and it was also confirmed from buoy temperature showing an occurrence number of 47 days. MHWs tended to be high in frequency in the coastal areas of Chungcheongdo and Jeollabukdo and the south coastal areas while in case of buoy temperature Jupo was the place of high frequency (32 days). This difference was supposed to be due to the low accuracy of satellite SST at the coasts. MHWs are also dominant in offshore waters around Korean Peninsula. Although detecting abnormal SST by using satellite SST has advantage of understanding occurrence from a spatial point of view, we also need to perform detection using buoys to increase detection accuracy along the coast.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.621-626
• /
• 2002

A satellite scatterometer is a microwave radar sensor used to measure the backscattering at a sea surface. This instrument transmits radar pulses to the sea surface and measure the radar energy reflected back towards the source. Changes in wind velocity make sea surface roughness change and then affect on backscattered power. This gives us information of sea surface wind speed. Directions of wind vectors are acquired by multiple, collocated, and nearly simultaneous measurements. It should be noted that the scatterometer observes not the wind directly but the wind stress vector relative to the surface current. This suggests the possibility that the satellite scatterometer winds can include the effect of the surface current. This study shows the evidence that scatterometer measure surface wind stress, not surface winds and presents the velocity structure of oceanic warm and cold eddies.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.30-33
• /
• 2005

Though sensible heat flux is one of heat flux components, it is generally considered that the importance is low compared with other components because of the small value. Actually sensible heat flux over the tropical ocean is extremely small, less than $100\;W/m^2$ .. However, it should be noted that sensible heat flux in boreal winter over the western boundary current regions is considerably large, about $100\;W/m^2$, and not neglected. In this study we carry out intercomparison of various global sensible heat flux data including not only satellite-derived data but also reanalysis data in order to clarify the characteristics of those data.