@Article{GalvãoBreTelGaiBal: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 and 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 = "03 jun. 2024"
}