LARS Tech Report Number
Multispectral scanner data were collected In two flights over ground cover plots near the Purdue University Agronomy Farm's Weather Station at an altitude of 305 m. Energy in eleven reflective wavelength bands from 0.46 to 2.6 µm was recorded by the scanner. A set of eight ground reflectance panels was in close proximity to the ground cover plots and was used to normalize the scanner data obtained on different dates. The ground reflectance panels were used to relate laboratory reflectance measurements to scanner response. Separate prediction equations were obtained for both flight dates for all eleven reflective wavelength bands of the multispectral scanner. In this way, scanner response was normalized to ground panel reflectance. By normalizing the scanner data, ratios of scanner data could be related to leaf area index over time.
Normalized scanner data were used to plot relative reflectance versus wavelength for the ground cover plots. Spectral response curves resulted which were similar to those for bare soil and green vegetation as determined by laboratory measurements. The spectral response of different ground cover plots represented a "mixing" of the spectral response curves for the bare soil and green vegetation components of the scene. The spectral response curves from the normalized scanner data indicated that reflectance in the 0.72 to 1.3 µm wavelength range increased as leaf area index increased. A decrease in reflectance was observed in the 0.65 µm chlorophyll absorption band as leaf area index increased. This confined the validity of using the ratio of the response from a near infrared wavelength band to that of the red wavelength band in relating multispectral scanner data to leaf area index in maize.
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