Agriculture Reference
In-Depth Information
Fig. 10.5
Principle of a
bi-spectral camera system for
the pixel congruent
acquisition of two images in
different spectral bands
(Sökefeld et al.
2007
)
computer
CCD
camera
EPROM
NIR
CCD
camera
beam
splitter
VIS
band-pass
filter
NIR &
VIS
image 610-690 nm (red)
a
IR-VIS difference image
binary image
C
d
b
image >700 nm
Fig. 10.6
Difference image (
c
) calculated from the infrared (
b
) and red image (
a
) to remove soil,
stones and mulch; followed by binarization (
d
) using automatic thresholding (Sökefeld et al.
2007
)
• Contour-based: these features were calculated from a contour representation of
the region. Fourier descriptors and curvature scale space representation (CSS)
were calculated (Mokhtarian et al.
1996
).
• Skeleton-based: the skeleton of a region is a “thinned” representation of the
region (Soille
2003
). Several numerical features as well as structural ones can be
derived from the skeleton.
