@Article{GalvăoSouzBreu:2020: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 = "2020",
volume = "57",
number = "1",
pages = "74--90",
month = "jan.",
keywords = "EO-1, Hyperion, orbit change, solar illumination effects, tropical
forests, Amazon, hyperspectral, vegetation indices.",
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 = "self-archiving-INPE-MCTIC-GOV-BR",
language = "en",
targetfile = "galval_hyperspectral.pdf",
urlaccessdate = "28 abr. 2024"
}