THE USE OF NARROW SPECTRAL BANDS FOR IMPROVING REMOTE SENSING ESTIMATIONS OF FRACTIONALLY ABSORBED PHOTOSYNTHETICALLY ACTIVE RADIATION
THE USE OF NARROW SPECTRAL BANDS FOR IMPROVING REMOTE SENSING ESTIMATIONS OF FRACTIONALLY ABSORBED PHOTOSYNTHETICALLY ACTIVE RADIATION
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Date
1994
Authors
Kim, Moon Sung
Advisor
Townshend, John R.G.
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Abstract
Most remote sensing estimations of vegetation variables such as leaf area index
(LAI), absorbed photosynthetically active radiation (Apar,), and primary production are
made using broad band sensors with a bandwidth of approximately 100 nm. However,
high resolution spectrometers are available and have not been fully exploited for the
purpose of improving estimates of vegetation variables. The study was directed to
investigate the use of high spectral resolution spectroscopy for remote sensing
estimates of f apar in vegetation canopies in the presence of nonphotosynthetic
background materials such as soil and leaf litter.
A high spectral resolution measure defined as the chlorophyll absorption ratio
index (CARI) was developed for minimizing the effects of nonphotosynthetic materials
in the remote estimates of f apar CARI utilizes three bands at 550, 670, and 700 nm
with bandwidth of 10 nm. Simulated canopy reflectance of a range of leaf area index
(LAI) were generated with the SAIL model using measurements of 42 different soil
types as canopy background. CARI calculated from the simulated canopy reflectance
was compared with the broad band vegetation indices such as normalized difference
vegetation index (NDVI), soil adjusted vegetation index (SAVI), and simple ratio (SR).
CARI reduced the effect of nonphotosynthetic background materials in the assessment
of vegetation canopy f apar more effectively than broad band vegetation indices.