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6.0 CONCLUSIONS
Preliminary validation tests indicate that using linear spectral
unmixing to extract the crop endmember (gap) fraction has
potential for the estimation of the effective LAI. Results for
bean, canola, and wheat showed a reasonable agreement with
LAI derived from direct measurements considering the
uncertainty in foliage distribution patterns (clumped, random,
or regularly) and in locating the sample plots in the imagery.
A comparison with LAI values calculated with a semi-
empirical approach using NDVI and those estimated from the
image fraction indicate that the two values agree within a
standard deviation of at most 0.3. The proposed fechnique has
the advantage that crop specific fractions can be determined
and, therefore, unwanted portions of vegetation such as weeds
can be excluded. This is not the case for LAI estimations
based on vegetation indices such as NDVI.
7.0 ACKNOWLEDGEMENT
The authors thank C. Burke for word-processing of this paper.
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