4. Results
We did an analysis in accordance with the band of OCTS. In this section, the
characteristic of BRDF by the difference of height of grass is shown(Fig3.1 ~ 3.3). Using
analyzing data in this section is that I observed in, 17:00 on August 9, 1998 here and we are
using the data that I observed in 16:00 on August 19, 1999. Solar Zenith angle is regular almost
(about 50 deg.). And measurement area is same area.
The graph of Fig3.1.3.3 is shown BRDF on principal plane for each band.
(wavelength). Vertical axis of the graph is showing reflectance. The horizontal axis is
showing scan angle. When scan angle is less than 0, scan is showing backward scan. Drawing
of dot is grand truth data. Drawing of line is showing second regression curve. Function of
second regression curve is written down under the graph.
44.5 mm regression curve- - - -y = 1E-05x2 + 0.0009x + 0.1052 R 2 = 0.96924
72.5 mm regression curve -------y = 8E-06x2 + 0.0005x + 0.0818 R 2 = 0.9032
Fig. 3.1 Comparison of BRDF for different grass height (OCTS Band 4)
44.5 mm regression curve- - - -y = 2E-05x2 + 0.0014x + 0.1666 R 2 = 0.974
72.5 mm regression curve -------y = 7E-06x2 + 0.0009x + 0.1188 R 2 = 0.9779
Fig. 3.2 Comparison of BRDF for different grass height (OCTS Band 6)
44.5 mm regression curve- - - y = 4E-05x2 + 0.002x + 0.2658 R 2 = 0.9703
72.5 mm regression curve -------y = 3E-05x2 + 0.0014x + 0.2726 R 2 = 0.9927
Fig. 3.3 Comparison of BRDF for different grass height (OCTS Band 4)
5. Conclusions and Discussion
We understood the following as a result of processing.
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1.Band4 and Ban6 have most similar characteristics between BRDF and grass canopy height.
Smaller height of grass canopy is more large fluctuation of Reflectance for scan angle than
taller that.
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2. Band 8 has most interesting characteristics between BRDF and grass canopy height. When
scan is backward scan, reflectance of taller height of grass canopy is lager. When reflectance is foreward
scan is forward scan, reflectance of smaller height of grass canopy is lager. Therefor grass canopy smaller
height has more large fluctuation of Reflectance than smaller that.
Acknowledgement
We thank The local government in Mandalgobi, the Meteorological Center in
Mandalgobi and The Ministry for Nature and Environment, The Information and Computer
Center.
This work has been supported by CREST (Core Research for Evolutional Science and
Technology) of Japan Science and Technology Corporation (JST).
Reference
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Chihiro WATANABE, Yoshiaki HONDA, Koji KAJIWARA The Study of Bi-directional Reflectance
Distribution Function(BRDF) for Grassland, ACRS,p-23-1-5,1997
