23 September 1993 Water spectral libraries for the interpretation of image spectrometric data
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This paper reports the assessment of water reflectance spectra measured under controlled condition for analysis of the imaging spectrometry data of inland waters. The application of imaging spectrometry to the study of inland waters depends on a better understanding of the optical properties of the water components. To increase this understanding, a collection of water spectra has been measured under laboratory and ground control conditions as a part of an EOS interdisciplinary investigation. The radiometric measurement derived from those experiments is known as the Bidirectional Reflectance Function (BRDF). R was simulated using variations of a model derived from the two stream approximation of the radiative transfer equation (RTE) and compared to the BRDF. BRDF was also measured 'in situ' from a boat based spectrometer (BoaR) and from an helicopter based spectrometer (HeIR). Modelled R (MoIR), laboratory measured (BRDF) (LabR) and ground measured BRDF (BoaR and HeIR) were compared. They were also used to unmix the spectra of two different aquatic systems. Preliminary results show that at low chlorophyll and gilvin concentration, there is a good agreement between ModR and LabR, regardless of the model variation used. For both low and high inorganic matter concentration, the agreement between ModR and LabR is poor. All sets of data present the main features which characterize the high chlorophyll concentration reflectance spectra, but the amount of reflectance displayed by LabR and ModR is 50 times smaller than that measured in situ. When the different sets are used as input to unmixing algorithms they also yield different results.
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Evlyn M.N.L. Novo, Evlyn M.N.L. Novo, "Water spectral libraries for the interpretation of image spectrometric data", Proc. SPIE 1937, Imaging Spectrometry of the Terrestrial Environment, (23 September 1993); doi: 10.1117/12.157046; https://doi.org/10.1117/12.157046

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