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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

View-illumination effects on hyperspectral vegetation indices in the Amazonian tropical forest

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Author(s):
Galvao, Lenio Soares [1] ; Breunig, Fabio Marcelo [2] ; dos Santos, Joao Roberto [1] ; de Moura, Yhasmin Mendes [1]
Total Authors: 4
Affiliation:
[1] INPE, Div Sensoriamento Remoto, BR-12245970 Sao Jose Dos Campos, SP - Brazil
[2] UFSM, CESNORS, Dept Engn Florestal, BR-98400000 Frederico Westphalen, RS - Brazil
Total Affiliations: 2
Document type: Journal article
Source: International Journal of Applied Earth Observation and Geoinformation; v. 21, p. 291-300, APR 2013.
Web of Science Citations: 30
Abstract

Because of the pointing capability of the Hyperion/Earth Observing-One (EO-1) to improve the revisit time of the scene, temporal series of narrowband vegetation indices (VIs) can be generated to study the phenology of the Amazonian tropical forests. In this study, 10 selected narrowband VIs calculated from Hyperion nadir and off-nadir data and from different view directions (forward scattering and backscattering) were analyzed for their sensitivity to view-illumination effects along the dry season on the Seasonal Semi-deciduous Forest. Data analysis was also supported by PROSAIL modeling to simulate the spectral response of this forest type in both directions. Hyperion and PROSAIL results showed that the Enhanced Vegetation Index (EVI) and Photochemical Reflectance Index (PRI) were the two more anisotropic VIs, whereas the Normalized Difference Vegetation Index (NDVI), Structure Insensitive Pigment Index (SIPI) and the Vogelmann Red Edge Index (VOG) were comparatively less sensitive to view-illumination effects. When compared to the other VIs and because of the greater dependence on the near-infrared (NIR) reflectance, EVI showed a different spectral behavior. EVI increased from forward scattering to backscattering and with decreasing solar zenith angle (SZA) towards the end of the local dry season, due to reduction in shading and enhancement of the illumination effects. On the other hand. PRI was higher with increasing shading in the forward scattering direction, as deduced from the PROSAIL simulation. Results emphasized the importance of taking into account bidirectional effects when analyzing temporal series of VIs collected over tropical forests by imaging spectrometers with pointing capability or even by multispectral sensors with large field-of-view (FOV). (C) 2012 Elsevier B.V. All rights reserved. (AU)

FAPESP's process: 08/11499-8 - Spectral-angular dynamics of soybean varieties and relationships with yield from off-nadir MODIS, ALI and Hyperion data
Grantee:Lenio Soares Galvão
Support Opportunities: Regular Research Grants