1.7 Whiz Quiz Answers
- Because both types of trees will
appear as similar shades of green to the
naked eye, imagery (or photography)
using the visible portion of the spectrum
may not be useful. Trying to distinguish
the different types from aerial
photographs based on tree crown shape
or size might also be difficult, particularly
when the tree types are intermixed.
Looking at the reflectance curves for the
two types, it is clear that they would be
difficult to distinguish using any of the
visible wavelengths. However, in the
near-infrared, although both types reflect
a significant portion of the incident
radiation, they are clearly separable.
Thus, a remote sensing system, such as
black and white infrared film, which
detects the infrared reflectance around
0.8 mm wavelength would be ideal for this
purpose.
Back to the question...
- By combining different channels of
imagery representing different
wavelengths, we may be able to identify
combinations of reflectance between the
different channels which highlight features
that we would not otherwise be able to
see, if we examine only one channel at a
time. Additionally, these combinations
may manifest themselves as subtle
variations in colour (which our eyes are
more sensitive to), rather than variations
in gray tone, as would be seen when
examining only one image at a time.
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