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@Article{Galv„oBreTelGaiBal:2016:InTeIl,
               author = "Galv{\~a}o, L{\^e}nio Soares and Breunig, F{\'a}bio Marcelo and 
                         Teles, Thiago Sousa and Gaida, William and Balbinot, Rafaelo",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universidade Federal de Santa Maria (UFSM)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade Federal 
                         de Santa Maria (UFSM)} and {Universidade Federal de Santa Maria 
                         (UFSM)}",
                title = "Investigation of terrain illumination effects on vegetation 
                         indices and VI-derived phenological metrics in subtropical 
                         deciduous forests",
              journal = "Giscience \& Remote Sensing",
                 year = "2016",
               volume = "53",
               number = "3",
                pages = "360--381",
                month = "May",
             keywords = "MODIS, topographic effects, subtropical forests, phenological 
                         metrics, vegetation indices, RapidEye.",
             abstract = "We used RapidEye and Moderate Resolution Imaging Spectroradiometer 
                         (MODIS)/Terra data to study terrain illumination effects on 3 
                         vegetation indices (VIs) and 11 phenological metrics over seasonal 
                         deciduous forests in southern Brazil. We applied TIMESAT for the 
                         analysis of the Enhanced Vegetation Index (EVI) and the Normalized 
                         Difference Vegetation Index (NDVI) derived from the MOD13Q1 
                         product to calculate phenological metrics. We related the VIs with 
                         the cosine of the incidence angle i (Cos i) and inspected 
                         percentage changes in VIs before and after topographic 
                         C-correction. The results showed that the EVI was more sensitive 
                         to seasonal changes in canopy biophysical attributes than the NDVI 
                         and Red-Edge NDVI, as indicated by analysis of non-topographically 
                         corrected RapidEye images from the summer and winter. On the other 
                         hand, the EVI was more sensitive to terrain illumination, 
                         presenting higher correlation coefficients with Cos i that 
                         decreased with reduction in the canopy background L factor. After 
                         C-correction, the RapidEye Red-Edge NDVI, NDVI, and EVI decreased 
                         2%, 1%, and 13% over sunlit surfaces and increased up to 5%, 14%, 
                         and 89% over shaded surfaces, respectively. The EVI-related 
                         phenological metrics were also much more affected by topographic 
                         effects than the NDVI-derived metrics. From the set of 11 metrics, 
                         the 2 that described the period of lower photosynthetic activity 
                         and seasonal VI amplitude presented the largest correlation 
                         coefficients with Cos i. The results showed that terrain 
                         illumination is a factor of spectral variability in the seasonal 
                         analysis of phenological metrics, especially for VIs that are not 
                         spectrally normalized.",
                  doi = "10.1080/15481603.2015.1134140",
                  url = "http://dx.doi.org/10.1080/15481603.2015.1134140",
                 issn = "1548-1603",
             language = "en",
        urlaccessdate = "28 nov. 2020"
}


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