veg reflactance

FINE STRUCTURE IN THE SPECTRAL
REFLECTANCE OF VEGETATION AND SO I LS
V, C, VANDERBI LT
Purdue University/LARS
E, Re STONER
Earth Resources Laboratory/National
Aeronautics and Space Administration
L, Lt BIEHLj Bo F, ROBINSONj
R, A, WEISMILLER AND Ma E, BAUER
Purdue University/LARS
The spectral reflective response of
plants, soils, and rocks may contain in-
formation concentrated in relatively nar-
row spectral regions defined by the light
absorption properties of the constituent
atoms and molecules. The hope exists that
such information will be of value in re-
mote sensing in discriminating information
classes, in identifying growth stages and
stress conditions in crops, and in delin-
eating the chemical and physical proper-
ties of soils and rocks. Satellite sen-
sors measuring spectral regions possibly
as narrow as 0.02 pm, a spectral resolu-
tion significantly better than that (0.1
pm) of the Landsat multispectral scanner,
appear feasible .
Fine structure in crop spectra has
been reported by Collins who identified
a shift in the radiance of wheat measured
in the far red (near-infrared 0.73 pm)
wavelengths, a shift that occurs at the
onset of heading. Wiersma grouped spec-
tra from bare soil and vegetation and
found a significant amount of non-redun-
dant information in the near-infrared
wavelength region in bands 0.02 pm apart.
The paper addresses the key issue
raised by Wiersma; if there is information
in narrow wavelength bands in reflectance
spectra of bare soil and vegetation, is
that information attributable to proper-
ties of the soil, the vegetation, or both.
Four hundred eighty-one spectra repre-
senting soils from throughout the United
States were analyzed. More than 1000
wheat spectra from fourfields measured
at four growth stages, several view direc-
tions, and several illumination angles
were analyzed. The analyses involved the
correlation coefficient computed for the
spectral reflectance of adjacent wave-
lengths 0.02 pm apart.
The analysis results show clearly the
large water absorption bands at 1.4 and
1.9 um, prominent in soil and vegetation
U.S. Government work not protected by U.S. copyright.
spectra, The iron oxide absorption band
at 0.9 um is quite pronounced in the anal-
ysis results of the soils data. The vege-
tation analysis results show clearly the
transition wavelength region between the
visible and the near-infrared, anomalies
at 0.53 and 0.57 pm, and minor water ab-
sorption bands at 0.95 and 1.15 pm. At
three wavelengths, 0.85, 1.05, and 1.25 pm,
small anomalies in the results may indi-
cate fine structure in the reflectance
data but the finding is tenuous at best.
1980 Machine Processing of Remotely Sensed Data Symposium