@Article{GalvăoSouzBreu:2019:HyExOv,
               author = "Galv{\~a}o, L{\^e}nio Soares and Souza, Alana Almeida de and 
                         Breunig, F{\'a}bio Marcelo",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade Federal 
                         de Santa Maria (UFSM)}",
                title = "A hyperspectral experiment over tropical forests based on the EO-1 
                         orbit change and PROSAIL simulation",
              journal = "GIScience and Remote Sensing",
                 year = "2019",
               volume = "56",
                pages = "1--17",
             keywords = "Hyperspectral Remote Sensing, Vegetation Indices, Hyperion/EO-1, 
                         solar zenith angle, solar illumination, Orbit drift.",
             abstract = "We designed a unique hyperspectral experiment from the Earth 
                         Observing One (EO-1) orbit change to evaluate solar illumination 
                         effects over tropical forests in Brazil. Ten nadir-viewing 
                         Hyperion images collected over a fixed site and period of the year 
                         (July to August) were selected for analysis. We evaluated 
                         variations in reflectance and in 16 narrowband vegetation indices 
                         (VIs) with increasing solar zenith angle (SZA) from the pre-drift 
                         (20042008) to the EO-1 drift period (20112016). To detect changes 
                         in reflectance and shadows, we applied spectral mixture analysis 
                         (SMA) and principal component analysis (PCA) and calculated the 
                         similarity spectral angle (\θ) between the vegetation 
                         spectra measured with variable SZA. The magnitude of the 
                         illumination effects was also evaluated from change-point analysis 
                         and nonparametric Mann-Whitney U tests applied over the time 
                         series. Finally, we complemented our experiment using the PROSAIL 
                         model to simulate the VIs variation with increasing SZA resultant 
                         from satellite drift. The results showed significant changes in 
                         Hyperion reflectance and VIs, especially when the EO-1 crossed the 
                         study area at earlier times and larger SZA in 2015 (9:05 a.m.; SZA 
                         = 59°) and 2016 (8:30 a.m.; SZA = 67°). Compared to the pre-drift 
                         period (10:30 a.m.; SZA = 45°), the SZA differences of 14° (2015) 
                         and 22° (2016) increased the shade fractions and decreased the 
                         vegetation brightness. PCA separated the pre-drift and drift 
                         reflectance datasets, showing shifts in scores due to changes in 
                         brightness. \θ increased with SZA, indicating changes in the 
                         shape of the vegetation spectra with drift. For most VIs, the 
                         change-point analysis indicated 2015 (SZA = 59°) as the 
                         predominant year of detected changes. Compared to the EO-1 
                         original orbit, the Plant Senescence Reflectance Index (PSRI), 
                         Anthocyanin Reflectance Index (ARI) and Structure Insensitive 
                         Pigment Index (SIPI) presented the largest positive changes during 
                         drift, while the Photochemical Reflectance Index (PRI), Visible 
                         Atmospherically Resistant Index (VARI) and Enhanced Vegetation 
                         Index (EVI) had the largest negative changes. The effect size of 
                         the illumination geometry on these VIs was large, as indicated by 
                         increasing values of the Cohens r metric toward 2016. The 
                         anisotropy of the Hyperion VIs was generally consistent with that 
                         from PROSAIL in the simulated pre-drift and drift periods. 
                         Focusing on structural indices, it affected the relationships 
                         between VIs and simulated leaf area index (LAI) at large SZA.",
                  doi = "10.1080/15481603.2019.1668595",
                  url = "http://dx.doi.org/10.1080/15481603.2019.1668595",
                 issn = "1548-1603",
                label = "lattes: 5507769922001047 1 GalvaoAlmeBreu:2019:HyExOv",
             language = "en",
           targetfile = "galvao_hyperspectral.pdf",
        urlaccessdate = "27 abr. 2024"
}