134 
(a) NDVI using uncorrected radiances (b) NDVI using corrected radiances 
Figure 6 . Effect of atmospheric correction on NDVI vegetation index 
ACKNOWLEDGEMENTS 
The authors would like to thank Larry Biehl and Purdue University for supplying the Purdue Soils Reflectance 
Database, and Stephane Jacquemoud for supplying source code for the PROSPECT model. 
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USDA-AR' 
LEE 
ABSTRACT: 
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for vegetation studie; 
appearance of clouds 
Consequently, select 
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NDVI varies with th 
tended to favor the c 
affected. To improve 
NDVI need to be mi 
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characteristics of ve; 
replaced with differe: 
in Niger in 1992. T 
promising towards th 
limitations will be ft 
KEY WORDS: Сот 
INTRODUCTION 
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data at regional and 
of the AVHRR dau 
calibrations of the se 
external problems ar 
angle variations. Coi 
making a quantitativ 
Compositin 
masking. These tec 
contaminations from 
value compositing ( 
within which the no 
compositing period, 
poor atmospheric cc 
NDVI presumably i 
angle data. Because 
composited data re] 
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of the nature of the ] 
to soil background 
maximum NDVI fai 
selection of highest 
and the view angle e 
type of noise.