Identification and Disease Index Inversion of Wheat Stripe Rust and Wheat Leaf Rust Based on Hyperspectral Data at Canopy Level

Table 1

The feature parameters in the third group of spectral features.

Feature parameter	Definition or calculation formula	Reference
b	The maximum of first derivatives within blue edge (490–530 nm)	[4]
λb	Wavelength at the position of b (nm)	[4]
y	The maximum of first derivatives within yellow edge (550–582 nm)	[4]
λy	Wavelength at the position of y (nm)	[4]
r	The maximum of first derivatives within red edge (680–780 nm)	[4]
λr	Wavelength at the position of r (nm)	[4]
g	The maximum reflectance in 510–560 nm	[4]
λg	Wavelength at the position of g (nm)	[4]
r	The minimum reflectance in 640–680 nm	[4]
	Wavelength at the position of r (nm)	[4]
b	Sum of first derivatives within blue edge (490–530 nm)	[4]
y	Sum of first derivatives within yellow edge (550–582 nm)	[4]
r	Sum of first derivatives within red edge (680–780 nm)	[4]
g/r	The ratio of g to r	[4]
(g  −  r)/(g + r)	The normalized value of g and r	[4]
r/b	The ratio of r to b	[4]
r/y	The ratio of r to y	[4]
(r −  b)/(r +  b)	The normalized value of r and b	[4]
(r −  y)/(r +  y)	The normalized value of r and y	[4]
Anthocyanin reflectance index (ARI)		[26]
Chlorophyll absorption ratio index (CARI)	in which, ,	[27]
Photochemical reflectance index (PRI)		[28]
Plant senescence reflectance index (PSRI)		[29]
Triangular vegetation index (TVI)		[30]
Water index (WI)		[31]