• Korean Journal of Remote Sensing
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• v.37 no.4
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• pp.687-698
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• 2021

We present quantitative estimations of changes in the areal extent of coral reef habitats at Weno Island, Micronesia, using high-spatial-resolution remote sensing images and field observations. Coral reef habitat maps were generated from Kompsat-2 satellite images for September 2008 and September 2010, yielding classifications with 78.6% and 72.4% accuracy, respectively, which is a relatively high level of agreement. The difference between the number of pixels occupied by each seabed type was calculated, revealing that the areal extent of living corals decreased by 8.2 percentage points between 2008 and 2010. This result is consistent with a comparison of the seabed types determined by field observations. This study can be used as a basis for remediation planning to diminish the impact of changes in coral reefs.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.181-186
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• 2006

Geostationary Orbit satellite, unlike other sun-synchronous polar-orbit satellites, will be able to take a picture of a large region several times a day (almost with everyone hour interval). For geostationary satellite, the target region is fixed though the location of sun is changed always. However, Sun-synchronous polar-orbit satellites able to take a picture of target region same time a everyday. Thus Ocean signal is almost same. Accordingly, the ocean signal of a given target point is largely dependent on time. In other words, the ocean signal detected by geostationary satellite sensor must translate to the signal of target when both sun and satellite are located in nadir, using another correction model. This correction is performed with a standardization of signal throughout relative geometric relationship among satellite-sun-target points. This relative ratio called bidirectional factor. To find relationship between time and $[L_w]_N$/Bidirectional Factor differences, we are calculate solar position, geometry parameters. And reflectance, total radiance at the top of atmosphere(). And water leaving radiance, normalized water leaving radiance. And calculate bidirectional factor, that is the ratio of $[L_w]_N$ between target region and aiming the point. Then, we can make the bidirectional factor lookup table for one year imaging. So, we suggested for necessary to simulation experiment bidirectional factor in more various condition(wavelength and ocean/air condition).

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.645-648
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• 2005

The COMS(Communication, Ocean and Meteorological Satellite), a multi-mission geo-stationary satellite, is being developed by KARl. The first mission of the COMS is the meteorological image and data gathering for weather forecast by using a five channel meteorological imager. The second mission is the oceanographic image and data gathering for marine environment monitoring around Korean Peninsula by using an eight channel Geostationary Ocean Color Imager(GOCI). The third mission is newly developed Ka-Band communication payload certification test in space by providing communication service in Korean Peninsula and Manjurian area. There were many low Earth orbit satellites for ocean monitoring. However, there has never been any geostationary satellite for ocean monitoring. The COMS is going to be the first satellite for ocean monitoring mission on the geo-stationary orbit. The meteorological image and data obtained by the COMS will be distributed to end users in Asia-Pacific area and it will contribute to the improved weather forecast.

• Korean Journal of Remote Sensing
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• v.29 no.6
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• pp.601-610
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• 2013

As a standard water clarity variable, the vertical underwater visibility, called Secchi depth, is estimated with ocean color satellite data. In the present study, Moderate Resolvtion Imaging Spectradiometer (MODIS) data are used to measure the Secchi depth which is a useful indicator of ocean transparency for estimating the water quality and productivity. To estimate the Secchi depth $Z_v$, the empirical regression model is developed based on the satellite optical data and in-situ data. In the previous study, a semi-analytical algorithm for estimating $Z_v$ was developed and validated for Case 1 and 2 waters in both coastal and oceanic waters using extensive sets of satellite and in-situ data. The algorithm uses the vertical diffuse attenuation coefficient, $K_d$($m^{-1}$) and the beam attenuation coefficient, c($m^{-1}$) obtained from satellite ocean color data to estimate $Z_v$. In this study, the semi-analytical algorithm is validated using temporal MODIS data and in-situ data over the Yellow, Southern and East Seas including Case 1 and 2 waters. Using total 156 matching data, MODIS $Z_v$ data showed about 3.6m RMSE value and 1.7m bias value. The $Z_v$ values of the East Sea and Southern Sea showed higher RMSE than the Yellow Sea. Although the semi-analytical algorithm used the fixed coupling constant (= 6.0) transformed from Inherent Optical Properties (IOP) and Apparent Optical Properties (AOP) to Secchi depth, various coupling constants are needed for different sea types and water depth for the optimum estimation of $Z_v$.

• Ocean Science Journal
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• v.40 no.2
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• pp.67-78
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• 2005

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and $54\;mg\;m^{-3}$ inside Jin-hae Bay and adjacent coastal bays and 0.5 and $8\;mg\;m^{-3}$ in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature $(\theta)$ and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water $(\theta and warm and high saline subsurface water $({\theta}>12^{\circ}C; S>34.4)$ at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.231-236
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• 1999

Accurate ocean surface fluxes with high resolution are critical for understanding a mechanism of global climate. However, it is difficult to derive those fluxes by using ocean observation data because the number of ocean observation data is extremely small and the distribution is inhomogeneous. On the other hand. satellite data are characterized by the high density, the high resolution and the homogeneity. Therefore, it can be considered that we obtain accurate ocean surface by using satellite data. Recently we constructed ocean surface data sets mainly using satellite data. The data set is named by Japanese Ocean Flux data sets with Use of Remote sensing Observations (J-OFURO). Here, we introduce J-OFURO. The data set includes shortwave radiation, longwave radiation, latent heat flux, sensible heat flux, and momentum flux etc. Moreover, sea surface dynamic topography data are included in the data set. Radiation data sets covers western Pacific and eastern Indian Ocean because we use a Japanese geostationally satellite (GMS) to estimate radiation fluxes. On the other hand, turbulent heat fluxes are globally estimated. The constructed data sets are used and shows the effectiveness for many scientific studies.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.6-11
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• 2002

A term of GNSS(Global Navigation Satellite System) is widely used to represent a navigation method for global area using satellite in space orbit 1his system can provide accurate and continuous position, and timing sources synchronized to UTC. There are, however, certain disadvantage that system can not operate without line of sight environment to satellite, or system failure of either satellite or control station. It is the pseduolite technology for using indoor and also for back-up equipment of foreign system failure. Especially, ocean applications widely use the GNSS system for navigation, surveying, timing, and management of traffic, so, system failure of GNSS will be very critical problem to affect many aspects of ocean field. In this paper, we experimented the pseudolite technology for several application field to compare the result in different environment. We used the common CDGPS algorithm for in-door navigation and experimented in ocean engineering basin with metallic wall and gymnasiums with concrete wall. We also investigated the comparison result and considerations for ocean applications of pseudolite technology.

• Proceedings of the KSRS Conference
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• v.2
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• pp.816-819
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• 2006

One of the most difficult parameters to measure in the sea is current speed and direction. Recently, efforts are being made to estimate the ocean current vectors by utilizing sequential satellite imageries. In this study, we attempted to estimated sea surface current vector (sscv) by using satellite ocean color imageries of SeaWifs around the Korean Peninsula. This ocean color image data has 1-day sampling interval and spatial resolution of 1x1 km. Maximum cross-correlation method is employed which is aimed to detect similar patterns between sequential images. The estimated current vectors are compared to the surface geostrophic current vectors obtained from altimeter of sea level height data. In utilizing the color imagery data, some limitations and drawbacks exist so that in warm water region where phytoplankton concentration is relatively lower than in cold water region, estimation of sscv is poor and unreliable. On the other hand, two current vector fields agree reasonably well in the Korean South Sea region where high concentration of chlorophyll-a and weak tide is observed. In the future, with ocean color images of shorter sampling interval by COMS satellite, the algorithm and methodology developed in the study would be useful in providing the information for the ocean current around Korean Peninsula.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.366-368
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• 2022

지구온난화에 따른 우리나라 주변 환경의 변화와 최근 중국 불법 어선의 연근해 어업 자원의 고갈 등으로 인해 우리나라 연근해 어족자원을 보호할 필요성이 증대되고 있으며, 지속 가능한 어업을 위해서는 어획물의 종류와 양을 정확히 파악하고 불법 어업에 대한 철저한 감시 및 관리가 필요하다. 이러한 시공간적으로 다양하게 변하는 생태 및 어장 환경 정보와 선박에 대한 정보를 통해 해양관측과 위성 원격탐사를 동시에 이용함으로써 근해와 원양 생물자원 실태를 관측하는 것이 가능하다. 본 연구에서는 NOAA-20 위성의 VIIRS (Visible Infrared Imaging Radiometer Suite) DNB (Day & Night Band) 영상을 기반으로 추정한 야간 불빛 자료를 활용하고자 한다. DNB 불빛 영상은 낮은 조도의 불빛을 감지하여 그 정보를 보여 준다. 야간 불빛 자료에 포함된 구름 부분을 마스킹하기 위해 NASA의 신규알고리즘이 적용된JPSS-JRR-CloudMask 기술을 이용하였다. 이번 연구에서는 구름의 영향이 없는 날짜를 선별한 후 AIS 정보에서 어선의 정보를 추출하여 검증 자료로 사용하였다. 실제 선박의 정보를 이용한 위성 불빛 자료의 검증을 통해 위성자료의 신뢰성을 확보하고 향후 불빛과 선단 규모의 상관관계 분석 및 어선의 분포 경향 분석을 통하여 우리나라의 어장환경 분석에 활용 가능할 것으로 기대한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.344-351
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• 2005

It was discussed to satellite based DCS (NOAA, Orbcomm, ADEOS-II, CBERS in polar satellite and GMS, GOES, METEOSAT, INSAT, FY-2 in geostationary satellite) with PTT (Platform Transmitter Terminal) and DCP (Data collection Platform) in order to application of real-time DCS (Data Collection System) in the ocean and fisheries. For covering ocean data link area in the eastern hemisphere, it was proposed to take DCS on the Korean geostationary satellite in the marine environments.