177 
important? Is there information within 
the imagery that explains spurious 
results? What kind and how extensive 
ground truth is available from other 
sources, or can be afforded? Answers 
to such questions will determine not 
only whether a proposed application is 
technically feasible, but will also 
guide the procedures that will enable 
those that are technically feasible to 
be successfully consummated. 
To date SCA has been applied to data 
for grain sorghum, wheat, cotton, maize 
and rice. Exemplary functional 
relations for the terms in Eqs. [1], 
[2], and [3] have been obtained that 
document its utility and suggest 
additional testing under a range of 
climatic conditions. For research 
purposes, data from a common source, 
such as LANDSAT TM or SPOT HRV, and 
ground truth observations for the same 
crops in various places in the world 
need to be acquired and compared. But 
application in operational settings 
such as described in the preceding 
paragraph need to proceed 
simultaneously. 
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