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SRS Sensors
of photosynthetic vegetation in the field of view of a radiometer.
See Royo and Dolors (2011) for an extensive introduction to using
spectral indices for plant canopy measurements.
Figure 3: Reflectance spectra for bare soil (Soil) and a healthy
wheat crop at various stages of development: heading (H), anthesis
(A), milk-grain stage (M), and post maturity (PM). Consider two
things about this figure: First, the considerable difference between
reflectance spectra from the soil and all stages of plant
development. Second, the changes in the visible spectra as the
canopy matures and senesces. We reproduced this figure with
permission from Royo and Dolors (2011).
Calculate NDVI with equation 1.
Where, ρ
and ρ
red
infrared (NIR). We assume percent reflectance to be the ratio of re-
flected to incident radiation in the specified waveband. A detailed
description of how to calculate reflectances from measured radiation
values is provided in equation number 4. NDVI has been shown to
ρ
N DV I =
ρ
are percent reflectances in the red and near
N IR
7
ρ
N IR
red
+ ρ
N IR
red
3 THEORY
(1)
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