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EFFECTS OF LEAF WATER CONTENT ON REFLECTANCE

EFFECTS OF LEAF WATER CONTENT ON REFLECTANCE. By: Ng Chun Qi Joy Toh Yun Ying Lam Chee Yong Leslie NUS High School of Math and Science Mentors: Dr Liew Soo Chin Mr Chang Chew Wai Center for Remote Imaging Sensing and Processing, NUS. What is Reflectance?.

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EFFECTS OF LEAF WATER CONTENT ON REFLECTANCE

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  1. EFFECTS OF LEAF WATER CONTENT ON REFLECTANCE By: Ng Chun Qi Joy Toh Yun YingLam Chee Yong Leslie NUS High School of Math and Science Mentors: Dr Liew Soo Chin Mr Chang Chew Wai Center for Remote Imaging Sensing and Processing, NUS

  2. What is Reflectance? • A measurement of the fraction of incident light energy reflected or scattered by the surface of an object • Wavelength and surface dependent • Influence of properties and conditions of target • Measured by a spectro-radiometer

  3. Unique Spectral Signature of Vegetation

  4. Put after intro. Name as intro(ctd) • Identify the relationship between the water content of leaves and its reflectance spectra • Species of interest: B. chinensis var. parachinesis (Common Name: Choy Sum 菜心)

  5. Add method

  6. The Experiment Fig. 1. Experimental Setup

  7. Workflow Analysis of Reflectance spectra Analysis of Reflectance spectra Identification of General Trends Identification of wavelengths with high correlation with EWT Analysis at specific wavelengths identified Analysis of correlation between combined reflectance and EWT

  8. Results: Typical leaf reflectance at different stages of oven heating

  9. Results: Linear Correlogram of Reflectance with EWT

  10. Results: Identification of wavelengths with high correlation with EWT • Further analysis carried out at 5 different wavelengths • 560nm, 680nm, 800nm, 1440nm and 1600nm • Correspondence to peaks and absorption bands in the reflectance spectra.

  11. Results: Reflectance vs EWT at 560nm Fig. 4: Reflectance vs EWT at 560nm

  12. Results: Reflectance vs EWT at 680nm Fig. 4: Reflectance vs EWT at 680nm

  13. Results: Reflectance vs EWT at 800nm Fig. 4: Reflectance vs EWT at 800nm

  14. Results: Reflectance vs EWT at 1440nm Fig. 4: Reflectance vs EWT at 1440nm

  15. Results: Reflectance vs EWT at 1600nm Fig. 4: Reflectance vs EWT at 1600nm

  16. Results:How to improve correlation? • Potential wavelengths that would be useful for characterization: 1400nm and 1600nm • Correlation can be improved by normalizing their reflectance at another suitably chosen wavelength: • R(1440)/R(560), R(1440)/R(680), R(1440)/R(800), R(1600)/R(560), R(1600)/R(680), and R(1600)/R(800)

  17. Results:Reflectance ratio R(1440)/R(560) vs EWT Fig. 9: Reflectance ratio R(1440)/R(560) vs EWT

  18. Results:Reflectance ratio R(1440)/R(680) vs EWT Fig. 9: Reflectance ratio R(1440)/R(680) vs EWT

  19. Results:Reflectance ratio R(1600)/R(800) vs EWT Fig. 9: Reflectance ratio R(1600)/R(800) vs EWT

  20. How can we approximate EWT from Reflectance? • where r is reflectance, w is EWT and a,b,c are fitting parameters

  21. Conclusion • Highest negative correlation of reflectance with EWT occurs at 1440nm • However, for space-borne sensors, the reflectance peak near 1600 nm should be used • Absorption band of atmospheric water vapour is near 1440nm • High water vapour content in the atmosphere would result in a low signal to noise ratio in this wavelength region.

  22. Conclusion • The correlation can be improved if reflectance ratios are used. • The ratios R(1440)/R(560) and R(1600)/R(800) seem to be optimal for the reflectance at 1440 nm and 1600 nm respectively.

  23. Applications • Non-destructive analysis of drought and flood conditions • Assessment of vegetation’s water content using wavelengths with high correlation with EWT and ratios of reflectance

  24. THANK YOU!

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