@Article{LiesenbergGalvPonz:2007:ImClBr,
               author = "Liesenberg, V. and Galv{\~a}o, L. S. and Ponzoni, F. J.",
          affiliation = "Instituto Nacional de Pesquisas Espaciais, Divis{\~a}o de 
                         Gera{\c{c}}{\~a}o de Imagens (INPE, DGI) and Instituto Nacional 
                         de Pesquisas Espaciais, Coordena{\c{c}}{\~a}o do Programa 
                         Amaz{\^o}nia (INPE, AMZ) and Instituto Nacional de Pesquisas 
                         Espaciais, Divis{\~a}o de Sensoriamento Remoto (INPE, DSR)",
                title = "Variations in reflectance with seasonality and viewing geometry: 
                         implications for classification of Brazilian savannah 
                         physiognomies with MISR/Terra data",
              journal = "International Journal of Remote Sensing",
                 year = "2007",
               volume = "107",
               number = "1-2",
                pages = "276--286",
             keywords = "Multi-angle Imaging SpectroRadiometer (MISR), savanna, 
                         classification, cerrado, view angle, sun zenith, Seasonality, 
                         imaging spectroradiometer, hyperspectral brdf data, land-cover 
                         types, Amazon (Region), multiangle, modis, retrieval, algorithm, 
                         angles.",
             abstract = "Bidirectional Reflectance Factor (BRF) data, collected at nine 
                         view angles, four bands and six dates by the Multi-angle Imaging 
                         SpectroRadiometer (MISR), were used to characterize the 
                         seasonality and viewing geometry effects on the discrimination of 
                         five selected physiognomies of a specific Brazilian savanna 
                         environment. Spectralangular profiles for each physiognomy 
                         (Seasonal, Dry and Pluvial Forests; Arboreous and Park Savanna) 
                         were obtained from nadir-normalized BRF data at each MISR band and 
                         date of image acquisition. The maximum likelihood classification 
                         technique was applied at each camera and date using a common set 
                         of pixels as training samples. A reference map was used as ground 
                         truth to obtain the classification accuracy for each physiognomy, 
                         view angle and date. Results showed that the surface anisotropy 
                         signatures of the savanna physiognomies were not unique and varied 
                         with Sun-view geometry and seasonality. Directional effects 
                         increased from data collected in the orthogonal plane to those 
                         acquired close to the solar principal plane, and with increasing 
                         Sun zenith angles. Such effects were also affected by seasonality 
                         due to differences in the dynamics of the vegetation response to 
                         precipitation, as indicated by the Fraction of Photosynthetically 
                         Active Radiation (FPAR) and Leaf Area Index (LAI) values. Dry 
                         Forest presented a faster rate of green-up in the beginning of the 
                         rainy season and more abrupt changes in LAI values earlier in the 
                         dry season than the other physiognomies. In relation to the nadir 
                         response, the strongest anisotropy was observed in the backward 
                         scattering direction and in the red band at large Sun zenith 
                         angles. Directional effects were also observed after the 
                         Normalized Difference Vegetation Index (NDVI) determination. 
                         Classification accuracy of vegetation improved from the rainy to 
                         the dry season. The exception was Park Savanna, which was also 
                         well discriminated from the other physiognomies in the beginning 
                         of the rainy season due to the spectral effects of 
                         non-photosynthetic vegetation (dry grass understore) that produced 
                         an increase in the red reflectance. In general, classification 
                         accuracy of the physiognomies improved also from the forward to 
                         the backward scattering direction. The best view angles for 
                         classification purposes ranged from 0° (nadir) to \− 45.6°, 
                         and were associated with viewing directions of maximum 
                         backscattering at the different dates. In comparison with single 
                         view direction results, the use of Anisotropy Index (ANIX) images 
                         produced a general decrease in classification accuracy values. 
                         Results indicated that off-nadir viewing can improve 
                         discrimination and mapping of major physiognomies in the Brazilian 
                         savanna environment.",
                  doi = "10.1016/j.rse.2006.03.018",
                  url = "http://dx.doi.org/10.1016/j.rse.2006.03.018",
                 issn = "0143-1161",
                label = "self-archiving-INPE-MCTIC-GOV-BR",
             language = "en",
           targetfile = "lenio2007.pdf",
        urlaccessdate = "21 maio 2024"
}