Agriculture Reference
In-Depth Information
Fig. 6.5
Sprayer boom with optical sensors for spot spraying of weeds in a fallow field (Courtesy
of Trimble Agric. Div., Westminster, USA, altered)
Fig. 6.6
Red edge inflection
points
red
near-infr.
0.3
red edge
infl. point
0.2
0.1
0
650 700 750
wavelength in nm
of the respective reflectance curve along the red edge meet. So the red edge inflection
point changes its position along the wavelength scale with the course of the spectrum.
If the algebraic formula of the reflectance within the red and adjacent near-infrared
range is known, this point can be calculated by differentiating twice and putting the
result of this equal to zero.
This method of calculating the red edge inflection point requires that the reflec-
tance data in the red and the adjacent near-infrared range are available with a high
spectral resolution. Therefore, many bands are needed and the method may become
expensive. For this reason, several indices that estimate the position of the inflection
