![](bg7.png)
Figure 8: Average of BP error for the cotton dataset.
Figure 9: Example of shadow present in soybean dataset.
posed to work with keypoints based methods, so that
spectral domain methods (e.g. Phase Correlation) can
be used in the registration process.
Our modification generated, for both datasets
evaluated, the same registration order as obtained by
the original framewrok. However, our approach has
considerably reduced its execution time, thus making
it feasible to apply to large datasets. Moreover, our
modification reduced the back projection error of the
alignment when compared with the spectral order.
Although several methods in the literature use spa-
tial methods for multispectral image alignment ob-
tained by UAVs, the quality obtained by the spectral
method (FFT-PC) was considerably superior, which
corroborates this approach as an alternative for multi-
spectral registration of images obtained by UAVs.
ACKNOWLEDGEMENTS
The authors gratefully acknowledges CAPES (Co-
ordination for the Improvement of Higher Edu-
cation Personnel) (Finance Code 001) and CNPq
(National Council for Scientific and Technologi-
cal Development, Brazil) (Grant #301715/2018-1)
for the financial support and the company Sensix
(http://sensix.com.br) for providing the images used
in the tests.
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