730 
resulted in a little improvement on soil noise reduction, while the sensitivity to vegetation changed little. The 
combination of the blue band and the modeled L function in ASVI not only increased the vegetation sensitivities, but 
simultaneously reduced the soil and atmospheric effects. All indices tested were similar in responses to view anal? 
variations, having a tendency to increase at large off-nadir view angles. 
In conclusion, no single vegetation index is ideal. The choice of vegetation indices in remote sensing 
applications depends both on the quality of the data and on the targets studied. For arid or semiarid regions such as 
north Africa where vegetation is sparse, the soil and atmosphere effects are pronounced. In this case, one may choose 
ASVI or SARVI. In regions such as tropical areas where substantial vegetation presents while the atmosphere varies 
frequently, then ASVI, ARVI, and GEMI are somewhat equivalent. For ground or aerial remote sensing measurements, 
where the atmosphere plays little role in the data quality, the MSAVI and SAVI may be used if vegetation density is 
low, and NDVI and MSAVI can be used at high vegetation covers. 
It should be pointed out that the results presented here were based on simulated data sets and limited number 
of measurements. Therefore, the statistical significance of these differences found among vegetation indices remain to 
be further validated with satellite- and ground-based measurements. It should also be pointed out that some vegetation 
indices use three bands while others use only two bands, which should be also taken into account in choosing vegetation 
indices. 
Acknowledgements: The authors are grateful to the USD A ARS Water Conservation Laboratory in Phoenix for financial 
support and Southwest Watershed Research Center in Tucson for providing a very convenient working environment. 
This work is also part of the NASA Interdisciplinary Research Program in Earth Sciences (NASA Reference Number 
IDP-88-086) at the University of Arizona (USA) and LERTS (Toulouse, France). 
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