BRDF Applications in Semiarid Grassland Monitoring with the AVHRRs
About these pages...
YES, I know, a lot of the links are broken. My apologies. If you have the
time and the energy, you are welcome to mail me new addresses or replacements.
Use of the Advanced Very High Resolution Radiometer (AVHRR) sensor flown
on the US' National Oceanic and Atmospheric Administration (NOAA) polar
orbiting satellites for biosphere monitoring applications (among others)
is seriously hampered by the fact that :
-
the satellite views a given location on the surface from many different
directions on subsequent orbits;
-
light from the sun doesn't hit a given location on the surface from the
same direction across the scanline, on subsequent orbits or at different
times of the year; and
-
land surfaces do not reflect incoming light equally in all directions as
a result of shadowing by protrusions (e.g. plants) and other interactions
(geometric effects and volume scattering).
However, if we can explain the processes behind the way land surfaces scatter
light in specific wavelengths through a model of some kind, then we can
correct the sensor data properly for these effects. In addition, we might
hope to find additional information on the characteristics of the surface
via the model's surface parameters, so this presents opportunities as well
as problems. Such a model is known as a BRDF model because it tries
to describe or explain the Bidirectional Reflectance
Distribution Function.
These pages show some of the results of fitting such a model to AVHRR
observations over the semiarid grasslands of Xilingol Aimag, Inner
Mongolia Autonomous Region, P.R. China; see also this
site and here.The
overall goal is to provide higher quality data from the AVHRR for community
type differentiation in the Inner Mongolia grasslands but there are
implications for all land remote sensing applications. The immediate aim
of this research is to assess the extent of the improvement in AVHRR data
quality possible operationally with BRDF correction and to evaluate the
information content of the BRDF model parameters.
A couple of links at the bottom
of the index page go to some non-BRDF pages... but most of this site is
related to BRDF Applications in Semiarid Grassland Monitoring with the
AVHRRs. Best viewed with a 17in monitor (or larger!)
Mirror
is here (not as recent)
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