• Ocean Science Journal
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• 제42권4호
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• pp.199-209
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• 2007

Empirical band-ratio algorithms and artificial neural network techniques to retrieve sea surface chlorophyll concentrations were evaluated in the Bohai Sea of China by using an extensive field observation data set. Bohai Sea represents an example of optically complex case II waters with high concentrations of colored dissolved organic mattei (CDOM). The data set includes coincident measurements of radiometric quantities and chlorophyll a concentration (Chl), which were taken on 8 cruises between 2003 and 2005, The data covers a range of variability in Chl in surface waters from 0.3 to 6.5 mg $m^{-3}$. The comparison results showed that these empirical algorithms developed for case I and case II waters can not be applied directly to the Bohai Sea of china, because of significant biases. For example, the mean normalized bias (MNB) for OC4V4 product was 1.85 and the root mean square (RMS) error is 2.26.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2001년도 춘계 학술대회 논문집 통권 4호 Proceedings of the 2001 KSRS Spring Meeting
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• pp.111-115
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• 2001

부유물이 해수의 광특성을 좌우하는 탁한 해수의 해색 분석 알고리즘을 개발하기 위하여 해수의 CASE-II water 원격반사도 모델이 개발되었다. 개발된 원격반사도 모델은 현장관측 자료와 비교 검정되었으며, 모델의 결과를 활용하여 지금까지의 단순 2 band ratio의 클로로필 알고리즘보다 발전된, 즉 부유물 농도의 함수로 새로운 개념의 알고리즘 개발이 시도하였다. 새 해색 클로로필 알고리즘을 SeaWiFS 위성 자료에 적용한 결과 만족스러운 결과를 얻을 수 있었다.

• Ocean Science Journal
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• 제42권1호
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• pp.49-59
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• 2007

Besides empirical algorithms with the blue-green ratio, the algorithms based on fluorescence are also important and valid methods for retrieving chlorophyll-a concentration in the ocean waters, especially for Case II waters and the sea with algal blooming. This study reviews the history of initial cognitions, investigations and detailed approaches towards chlorophyll fluorescence, and then introduces the biological mechanism of fluorescence remote sensing and main spectral characteristics such as the positive correlation between fluorescence and chlorophyll concentration, the red shift phenomena. Meanwhile, there exist many influence factors that increase complexity of fluorescence remote sensing, such as fluorescence quantum yield, physiological status of various algae, substances with related optical property in the ocean, atmospheric absorption etc. Based on these cognitions, scientists have found two ways to calculate the amount of fluorescence detected by ocean color sensors: fluorescence line height and reflectance ratio. These two ways are currently the foundation for retrieval of chlorophyll-a concentration in the ocean. As the in-situ measurements and synchronous satellite data are continuously being accumulated, the fluorescence remote sensing of chlorophyll-a concentration in Case II waters should be recognized more thoroughly and new algorithms could be expected.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.445-449
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• 2005

Various methods to detect the phytoplankton/red tide blooms in the oceanic waters have been developed and tested on satellite ocean color imagery since the last two and half decades, but accurate detection of blooms with these methods remains challenging in optically complex turbid waters, mainly because of the eventual interference of absorbing and scattering properties of dissolved organic and particulate inorganic matters with these methods. The present study introduces a new method called Red tide Index (Rl), providing indices which behave as a good measure of detecting red tide algal blooms in high scattering and absorbing waters of the Korean South Sea and Yellow Sea. The effectiveness of this method in identifying and locating red tides is compared with the standard Ocean Chlorophyll 4 (OC4) bio-optical algorithm applied to SeaWiFS ocean imagery, acquired during two bloom episodes on 27 March 2002 and 28 September 2003. The result revealed that OC4 bio-optical algorithm falsely identifies red tide blooms in areas abundance in colored dissolved organic and particulate inorganic matter constituents associated with coastal areas, estuaries and river mouths, whereas red tide index provides improved capability of detecting, predicting and monitoring of these blooms in both clear and turbid waters.

• 대한원격탐사학회지
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• 제39권6_2호
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• pp.1565-1576
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• 2023

천리안 해양위성 2호(Geostationary Ocean Color Imager-II, GOCI-II)에서 관측된 대기상층 복사휘도에서 해양환경 분석이 가한 원격반사도(remote-sensing reflectance, R_rs) 자료를 얻기 위해서 복사 전달 모델 기반의 대기 보정을 수행한다. 이 R_rs는 다시 엽록소, 총부유사, 용존유기물 농도 등의 다양한 해양환경변수 산출에 이용되고 있기 때문에 대기보정은 모든 해색 산출물의 정확도에 영향을 주는 중요한 알고리즘이다. 맑은 해역에서는 대기의 복사휘도가 청색 파장대의 해수 복사휘도보다 10배 이상 높다. 따라서 대기보정 과정에서 1%의 대기 복사휘도 추정 오차가 10% 이상의 R_rs 오차를 유발할 수 있으며, 이처럼 대기보정은 매우 높은 오차 민감도를 가진 알고리즘이다. 그 결과 대기보정 산출물인 R_rs의 품질 평가는 신뢰성 있는 해양 위성 기반 자료 분석을 위해 반드시 선행되어야 한다. 본 연구에서는 Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Bio-optical Archive and Storage System (SeaBASS)을 통해 데이터베이스화 된 현장 측정 R_rs 기반 통계적 신뢰성을 평가하는 Quality Assurance (QA) 알고리즘을 GOCI-II의 분광 특성에 맞게 수정 및 적용하였다. 이 방법은 National Oceanic and Atmospheric Administration (NOAA)의 해색위성 자료처리 시스템에 공식적으로 적용되어 서비스 중이며, R_rs의 품질 분석 점수(0~1점)를 제공할 뿐 아니라 해수의 유형(23 유형)도 구분해 준다. 실제로 검보정 초기 단계의 GOCI-II 자료에 QA를 적용한 결과, R_rs는 비교적 낮은 값인 0.625에서 가장 높은 빈도를 보여주었지만 추가적인 검보정을 통해 개선된 GOCI-II 대기보정 결과에 QA 알고리즘을 적용했을 시 기존보다 높은 0.875에서 가장 높은 빈도를 보여주었다. QA 알고리즘을 통한 해수 유형 분석 결과, 동해 및 남해 일부 그리고 북서태평양 해역은 주로 탁도가 낮은 case-I 해역이었으며 서해 연안 및 동중국해는 주로 탁도가 높은 case-II 해역으로 구분되었다. 이처럼 QA 알고리즘의 적용을 통해 대기보정 과정에서 오차가 크게 발생한 R_rs 자료를 객관적으로 판별하여 배제할 수 있으며 이는 배포자료 및 검보정의 신뢰도 향상으로 이어질 수 있다. 본 방법은 추후 GOCI-II의 대기보정 flag에 적용되어 사용자들이 양질의 R_rs 자료만을 적용할 수 있도록 도움을 줄 것이다.

• 한국수산과학회지
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• 제34권4호
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• pp.359-364
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• 2001

복수어구에 의한 단일 어종 자원의 평가모델은 단일 어종에 대한 복수어구의 어획노력량이 다르므로 어업별 어획노력량을 하나의 노력단위로 표준화하여, Fox (1970)에 의한 잉여생산량모델에 적용함으로써, 최대지속적생산량, 최대경제적생산량 및 적정어획 노력량의 값을 추정하였다. 여기서는 참조기에 대한 대형기선저인 망쌍끌이어업과 근해안강망어업에 대해 적용하였고, 이 두 어업에 대한 경제성 분석을 통하여 순이익을 추정하였다. 참조기에 대한 어업별 순이익의 변동을 비교 분석한 결과 두 어업의 경제성은 근해안강망어업이 대형기선저인망쌍끌이어업 보다 더 나은 것으로 분석되었으며, 두 어업의 순이익을 같게 하기 위해서는 대형기 선저인망쌍끌이어업의 노력량을 현재보다 증가시키고 근해안강망 어업의 노력량은 낮춰야 한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.25-28
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• 2006

We propose a new method of masking cloud-affected pixels in satellite ocean color imageries such as of GLI. Those pixels, mostly found around cloud pixels or in scattered cloud area, have anomalous features in either in chlorophyll-a estimate or in water reflectance. This artifact is most likely caused by residual error of inter-band registration correction. Our method is to check the pixel-wise 'soundness' of the spectral water reflectance Rw retrieved after the atmospheric correction. First, we define two spectral ratio between water reflectance, IRR1 and IRR2, each defined as RW(B1)/RW (B3) RW (B3) and as RW (B2)/RW(B4) respectively, where $B1{\sim}B4$ stand for 4 consecutive visible bands. We show that an almost linear relation holds over log-scaled IRR1 and IRR2 for shipmeasured RW data of SeaBAM in situ data set and for GLI cloud-free Level 2 sub-scenes. The method we propose is to utilize this nature, identifying those pixels that show significant discrepancy from that relationship. We apply this method to ADEOS-II/GLI ocean color data to evaluate the performance over Level-2 data, which includes different water types such as case 1, turbid case 2 and coccolithophore bloom waters.

• 한국환경보건학회지
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• 제28권2호
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• pp.61-69
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• 2002

Oship stream is located nearby south eastern coasts. This study was performed to find out waters quality modeling and then to predict water quality of Oship stream. Based on survey data, BOD, T-N, T-P calibration and verification result were in good agreement with measured value within mean coefficient variance(MSE) value, which were 13.9%, 9.0%, 26.5% and 19.5%, 12.0%, 16.5%, respectively. Sectional water quality predictions of the main stream of Oship stream are executed on the basis of the following cases 1) with sewage treatment of Dogye-eup 2) reduction of mine wastewater treatment of 80% in th basin. As a result, BOD, T-P improvement rates at down stream of Oship stream, case 1) were appeared 12.2%, 22.2%, case 2) maximum sulfate ion and conductivity reduction removal rate of Oship stream were 58%, 68%. The main pollution sources of Oship-stream were almost domestic wastewater and mine wastewater discharged from Dogye-eup which located in uppers stream. The large effects will appear after the construction of Dogye sewage water treatment plant which remove the organic matter and nutrients in these sewage water. The waste water from mine can not easily to treat for characteristics of effluence and economic problems. However, to achieve the goal of water quality in Oship-stream water system, treatments of those are necessary.

• 대한원격탐사학회지
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• 제21권3호
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• pp.173-188
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• 2005

The present study aims to derive and compare narrow and broad bandwidths of ocean color sensor’s algorithms for the study of monitoring highly dynamic coastal oceanic environmental parameters using high-resolution imagery acquired from Multi-spectral Camera (MSC) on KOMPSAT-2. These algorithms are derived based on a large data set of remote sensing reflectances ($R_{rs}$) generated by using numerical model that relates $b_b/(a + b_b)$ to $R_{rs}$ as functions of inherent optical properties, such as absorption and backscattering coefficients of six water components including water, phytoplankton (chl), dissolved organic matter (DOM), suspended sediment (SS) concentration, heterotropic organism (he) and an unknown component, possibly represented by bubbles or other particulates unrelated to the first five components. The modeled $R_{rs}$ spectra appear to be consistent with in-situ spectra collected from Korean waters. As Kompsat-2 MSC has similar spectral characteristics with Landsat-5 Thematic Mapper (TM), the model generated $R_{rs}$ values at 2 ㎚ interval are converted to the equivalent remote sensing reflectances at MSC and TM bands. The empirical relationships between the spectral ratios of modeled $R_{rs}$ and chlorophyll concentrations are established in order to derive algorithms for both TM and MSC. Similarly, algorithms are obtained by relating a single band reflectance (band 2) to the suspended sediment concentrations. These algorithms derived by taking into account the narrow and broad spectral bandwidths are compared and assessed. Findings suggest that there was less difference between the broad and narrow band relationships, and the determination coefficient $(r^2)$ for log-transformed data [ N = 500] was interestingly found to be $(r^2)$ = 0.90 for both TM and MSC. Similarly, the determination coefficient for log-transformed data [ N = 500] was 0.93 and 0.92 for TM and MSC respectively. The algorithms presented here are expected to make significant contribution to the enhanced understanding of coastal oceanic environmental parameters using Multi-spectral Camera.

• 대한원격탐사학회지
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• 제17권4호
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• pp.285-295
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• 2001

We developed a CASE-II water model that will enable the simulation of remote sensing reflectance($R_{rs}$) at the coastal waters for the retrieval of suspended sediments (SS) concentrations from satellite imagery. The model has six components which are: water, chlorophyll, dissolved organic matter (DOM), non-chlorophyllous particles (NC), heterotrophic microorganisms and an unknown component, possibly represented by bubbles or other particulates unrelated to the five first components. We measured $R_{rs}$, concentration of SS and chlorophyll, and absorption of DOM during our field campaigns in Korea. In addition, we generated $R_{rs}$ from different concentrations of SS and chlorophyll, and various absorptions of DOM by random number functions to create a large database to test the model. We assimilated both the computer generated parameters as well as the in-situ measurements in order to reconstruct the reflectance spectra. We validated the model by comparing model-reconstructed spectra with observed spectra. The estimated $R_{rs}$ spectra were used to (1) evaluate the performance of four wavelengths and wavelengths ratios for accurate retrieval of SS. 2) identify the optimum band for SS retrieval, and 3) assess the influence of the SS on the chlorophyll algorithm. The results indicate that single bands at longer wavelengths in visible better results than commonly used channel ratios. The wavelength of 625nm is suggested as a new and optimal wavelength for SS retrieval. Because this wavelength is not available from SeaWiFS, 555nm is offered as an alternative. The presence of SS in coastal areas can lead to overestimation chlorophyll concentrations greater than 20-500%.