sensitivity to leaf cover and color (Kochubey and Kazantsev, 2007). Well-described
details on derivatives of spectral reflectance can be found in, for example, Morrey
(1968).
15.2.2.4 Spectral Libraries Available from Field Spectra Data Sets A spectral
library is designed to hold pure spectra information of various land cover types in
order to assist spectral discrimination at the field scale and further large-scale imagery
mapping. In addition, the possibility of addressing the issue of mixed pixels,
Wavelength (nm)
400
500
600
700
800 900
Second-derivative reflectance
First-derivative reflectance
Reflectance
–0.0002
0.0001
0.0000
0.0001
0.0002
0.0003
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.00
0.10
0.20
0.30
0.40
FIGURE 15.3 Unaltered vegetation reflectance (upper graph) and its first (middle graph) and
second (lower graph) derivatives in 350–900-nm spectrum. The gray edge has an inflection
point (point where where the slope is maximum) at 730 nm. This corresponds to the maximum
in its first derivative and to local minimum in the second derivative (gray squares).
FIELD SPECTRORADIOMETRY
295