Relationship between remote sensing reflectance and optically active substances in case 1 and case 2 waters

1997 ◽  
Author(s):  
David A. Phinney
Keyword(s):  
Remote Sensing ◽  
Optically Active ◽  
Remote Sensing Reflectance ◽  
Active Substances ◽  
Optically Active Substances

scholarly journals Underwater Use of a Hyperspectral Camera to Estimate Optically Active Substances in the Water Column of Freshwater Lakes

2020 ◽  
Vol 12 (11) ◽  
pp. 1745
Author(s):  
Michael Seidel ◽  
Christopher Hutengs ◽  
Felix Oertel ◽  
Daniel Schwefel ◽  
András Jung ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Water Column ◽  
Hyperspectral Imaging ◽  
Quality Parameters ◽  
Optically Active ◽  
Freshwater Lakes ◽  
Active Substances ◽  
Optically Active Substances

Freshwater lakes provide many important ecosystem functions and services to support biodiversity and human well-being. Proximal and remote sensing methods represent an efficient approach to derive water quality indicators such as optically active substances (OAS). Measurements of above-ground remote and in situ proximal sensors, however, are limited to observations of the uppermost water layer. We tested a hyperspectral imaging system, customized for underwater applications, with the aim to assess concentrations of chlorophyll a (CHLa) and colored dissolved organic matter (CDOM) in the water columns of four freshwater lakes with different trophic conditions in Central Germany. We established a measurement protocol that allowed consistent reflectance retrievals at multiple depths within the water column independent of ambient illumination conditions. Imaging information from the camera proved beneficial for an optimized extraction of spectral information since low signal areas in the sensor’s field of view, e.g., due to non-uniform illumination, and other interfering elements, could be removed from the measured reflectance signal for each layer. Predictive hyperspectral models, based on the 470 nm–850 nm reflectance signal, yielded estimates of both water quality parameters (R² = 0.94, RMSE = 8.9 µg L−1 for CHLa; R² = 0.75, RMSE = 0.22 m−1 for CDOM) that were more accurate than commonly applied waveband indices (R² = 0.83, RMSE = 13.2 µg L−1 for CHLa; R² = 0.66, RMSE = 0.25 m−1 for CDOM). Underwater hyperspectral imaging could thus facilitate future water monitoring efforts through the acquisition of consistent spectral reflectance measurements or derived water quality parameters along the water column, which has the potential to improve the link between above-surface proximal and remote sensing observations and in situ point-based water probe measurements for ground truthing or to resolve the vertical distribution of OAS.

Plasmochemical Synthesis of Optically Active Substances

2021 ◽  
Vol 49 (3) ◽  
pp. 1050-1054
Author(s):  
Valeriy Ya. Chernyak ◽  
Vitalii V. Iukhymenko ◽  
Kostia V. Iukhymenko ◽  
Yevgen A. Oberemok ◽  
Daniil D. Tretiakov ◽  
...  
Keyword(s):  
Optically Active ◽  
Active Substances ◽  
Optically Active Substances

XVIII.—The Physical Properties of Mixed Solutions of Independent Optically - Active Substances

1907 ◽  
Vol 27 ◽  
pp. 172-180
Author(s):  
Clerk Ranken ◽  
W. W. Taylor
Keyword(s):  
Physical Properties ◽  
Active Substance ◽  
Optically Active ◽  
Present Communication ◽  
Points Of Interest ◽  
Systematic Examination ◽  
Mixed Solutions ◽  
Two Systems ◽  
Active Substances ◽  
Optically Active Substances

The two systems containing one of a pair of optically-active stereoisomers and an independent optically-active substance present many points of interest and importance, but have not hitherto been investigated with any degree of completeness. What is known about them may fairly be said to consist of a series of isolated facts. The present communication also contributes a few more isolated observations, and is, in reality, a preliminary to a more systematic examination of the whole subject.

scholarly journals Seasonal variation in optically active substances at a coastal site along western Bay of Bengal

2019 ◽  
Vol 1 (10) ◽  
Author(s):  
Chandanlal Parida ◽  
Sanjiba Kumar Baliarsingh ◽  
Aneesh Anandrao Lotliker ◽  
Madhusmita Dash ◽  
Suchismita Srichandan ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Bay Of Bengal ◽  
Optically Active ◽  
Coastal Site ◽  
Western Bay Of Bengal ◽  
Active Substances ◽  
Optically Active Substances
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