Announcing recent publication in Revista Brasileira de Cartographia (RBC) – the Brazilian Journal of Cartography. The full text is available open-access online: Streher et al., 2014, RBC, International Issue 66/7, 1437-1449.
Title: Sunglint Correction in Airborne Hyperspectral Images Over Inland Waters
Authors: Annia Susin Streher, Cláudio Clemente Faria Barbosa, Lênio Soares Galvão, James A. Goodman, Evlyn Marcia Leão de Moraes Novo, Thiago Sanna Freire Silva
Abstract: This study assessed sunglint effects, also known as the specular reflection from the water surface, in high-spatial and high-spectral resolution, airborne images acquired by the SpecTIR sensor under different view-illumination geometries over the Brazilian Ibitinga reservoir (Case II waters). These effects were corrected using the Goodman et al. (2008) and the Kutser et al. (2009) methods, and a Kutser et al. (2009) variant based on the continuum removal technique to calculate the oxygen absorption band depth. The performance of each method for reducing sunglint effects was evaluated by a quantitative analysis of pre- and post-sunglint correction reflectance values (residual reflectance images). Furthermore, the analysis was supported by inspection of the reflectance differences along transects placed over homogeneous masses of waters and over specific portions of the scenes affected and non-affected by sunglint. Results showed that the algorithm of Goodman et al. (2008) produced better results than the other two methods, as it approached zero amplitude reflectance values between homogenous water masses affected and non-affected by sunglint. The Kutser et al. (2009) method also presented good performance, except for the most contaminated sunglint portions of the scenes. When the continuum removal technique was incorporated to the Kutser et al. (2009) method, results varied with the scene and were more sensitive to atmospheric correction artifacts and instrument signal-to noise ratio characteristics.
Keywords: coral reefs; remote sensing; field spectra; scale; ecology; biodiversity; conservation hyperspectral remote sensing, specular reflection, water optically active substances, SpecTIR sensor
Figure 5. Deglinted SpecTIR hyperspectral of Ibitinga reservoir (São Paulo, Brazil) images and resultant reflectance profiles after correction by the methods of: (a) Goodman et al. (2008); (b) Kutser et al. (2009); and (c) modified Kutser et al. (2009).