Yeap, Eng Choo
(2020)
Development Of An Algorithm To
Reduce The Topographical Effects In
Reflected Radiance.
PhD thesis, Universiti Sains Malaysia.
Abstract
Topographic effects in satellite images are not errors but distortions caused by
the solar and surface geometry. Surfaces facing towards the Sun tend to be brighter
while surfaces facing away from the Sun are generally darker. This effect is strongly
related to solar surface incident angle, and it is one of the main factors that increase
spectral variation in satellite images. Spectral variation may reduce accuracy, such as
non-supervised classification, which can limit the capability of autonomous remote
sensing applications. Many researchers have tried to reduce the effect of topography
in the past with success; however, most of these methods are complicated and require
many parameters. To address this problem, we developed algorithms that quantify,
reduce, and induce topographical effects in satellite images by exploring the
relationship between direct and diffuse solar irradiance. These algorithms use data
from extraterrestrial irradiance, atmospheric profiles, digital elevation models, and
radiative transfer models to calculate the amount of irradiance on Earth’s surface to
reduce distortions due to the topographic effect. The algorithm was tested on 11
Landsat 8 OLI satellite images assessed with 120 sample points each. The results
demonstrate that this approach suppresses the topographic effect and improves spectral
signatures and similarities between satellite images taken on different dates using
topographic induction.
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