• 대한원격탐사학회지
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• 제20권5호
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• pp.289-305
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• 2004

Atmospheric correction of Landsat Visible and Near Infrared imagery (VIS/NIR) over aquatic environment is more demanding than over land because the signal from the water column is small and it carries immense information about biogeochemical variables in the ocean. This paper introduces two methods, a modified dark-pixel substraction technique (path--extraction) and our spectral shape matching method (SSMM), for the correction of the atmospheric effects in the Landsat VIS/NIR imagery in relation to the retrieval of meaningful information about the ocean color, especially from Case-2 waters (Morel and Prieur, 1977) around Korean peninsula. The results of these methods are compared with the classical atmospheric correction approaches based on the 6S radiative transfer model and standard SeaWiFS atmospheric algorithm. The atmospheric correction scheme using 6S radiative transfer code assumes a standard atmosphere with constant aerosol loading and a uniform, Lambertian surface, while the path-extraction assumes that the total radiance (L/sub TOA/) of a pixel of the black ocean (referred by Antoine and Morel, 1999) in a given image is considered as the path signal, which remains constant over, at least, the sub scene of Landsat VIS/NIR imagery. The assumption of SSMM is nearly similar, but it extracts the path signal from the L/sub TOA/ by matching-up the in-situ data of water-leaving radiance, for typical clear and turbid waters, and extrapolate it to be the spatially homogeneous contribution of the scattered signal after complex interaction of light with atmospheric aerosols and Raleigh particles, and direct reflection of light on the sea surface. The overall shape and magnitude of radiance or reflectance spectra of the atmospherically corrected Landsat VIS/NIR imagery by SSMM appears to have good agreement with the in-situ spectra collected for clear and turbid waters, while path-extraction over turbid waters though often reproduces in-situ spectra, but yields significant errors for clear waters due to the invalid assumption of zero water-leaving radiance for the black ocean pixels. Because of the standard atmosphere with constant aerosols and models adopted in 6S radiative transfer code, a large error is possible between the retrieved and in-situ spectra. The efficiency of spectral shape matching has also been explored, using SeaWiFS imagery for turbid waters and compared with that of the standard SeaWiFS atmospheric correction algorithm, which falls in highly turbid waters, due to the assumption that values of water-leaving radiance in the two NIR bands are negligible to enable retrieval of aerosol reflectance in the correction of ocean color imagery. Validation suggests that accurate the retrieval of water-leaving radiance is not feasible with the invalid assumption of the classical algorithms, but is feasible with SSMM.

• 융합신호처리학회논문지
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• 제21권1호
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• pp.38-48
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• 2020

기존에 건조되어 있거나, 신규로 건조되고 있는 선저를 검사하기 위해선 전문 잠수부가 직접 수중 하부에서 육안으로 검사를 한다. 하지만 직접 사람이 하는 일이기 때문에 인명사고, 충돌사고 등 많은 위험이 뒤따른다. 이를 해결하기 위해 Visual Inspection을 위한 선박 검사용 수중 드론 개발이 필요하다. 수중 드론에 적용되는 기술과 각 부품의 용도와 제작 과정, 펌웨어 개발과 같은 제작 방법에 관해 기술하였으며 수중에서 드론 자체의 주행 능력과 크롤러를 이용한 주행 능력을 측정하여 차이를 비교해보고 위치 추적 장치 테스트를 통해 실제 위치와의 오차를 확인하였다. 본 연구를 통해 제작된 수중 드론을 작업 현장에서 사용하였을 때 인명사고를 예방하고 경제적 효과와 안정성을 얻을 것으로 기대된다.