The Study on generating of BRDF table set for Multi Channel Sensor
4. Results and Conclusion
We could obtain many spectral data in some different geometry condition. Table.2 is data list that we could measure by day and obtain good data for analysis. And these three areas are different of field condition. Following result are measurement data at the 9
th Aug (Fig.2).
Results are shown Fig.4-8 Fig.4 and Fig.5 are spectral reflectance characteristics as change the solar zenith angle. As you can see from Fig.3 and Fig.4, the sensor zenith angle is the greater and greater, spectral reflectance is the higher and higher all over the wavelength.
Fig.6 and Fig.7 are depict the 3-D plotting of directional reflectance profiles as change the sensor angle in the red region (580nm-680nm) and in the near infrared region (725nm-920nm) respectively. -y axis indicates the direction of sun (forward scan). +y axis indicate the backward direction (backward scan). Distance from the origin to point on the x-y surface. First, we could understand that directional reflectance profiles differ with sensor angle. And that is different according with wavelength region. In the infrared region is more large effect a change than in red region.
Fig.8 are directional reflectance characteristics as change the sensor scan angle every different the solar zenith angle in the infrared region. When scan angle is -, it indicates forward scan. Backward scan is more large effect a change than scan.
Fig. 3 Measurement Geometric condition
Fig.4 the Spectral Reflectance characteristic (The Sensor Zenith Angle is 0 deg)
Fig. 5 the Spectral Reflectance Characteristic (The Sensor Zenith Angle is 60 deg)
Fig.6 the Directional Reflectance Profile in the RED (580-680nm)
Fig.7 the Directional Reflectance Profile in the RED (725-920nm)
Fig. 8 Directional Reflectance Characteristics
5. Discussion
When we develop composite algorithm that takes BRDF into consideration, we should consider about reflectance characteristics of the following.
-
Different with sun zenith angle.
- Different with sun azimuth angle.
- Different with sensor scan angle.
- Different with wavelength.
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, KAJIWARA The Study of Bi-directional Reflectance Distribution Function (BRDF) for Grassland, ACRS,p-23-1-5,1997
