Dynamic monitoring of biomass of rice under different nitrogen treatments using a lightweight UAV with dual image-frame snapshot cameras

Table 1 Vegetation indices (VIs) derived from red green blue (RGB) and multispectral images

Vegetation indices	Definition	References
RGB-VIs
Visible-band difference vegetation index	VDVI = (2 * G − R − B)/(2 * G + R + B)	[37]
Normalized green–red difference index	NGRDI = (G − R)/(G + R)	[43]
Visible atmospherically resistant index	VARI = (G − R)/(G + R – B)	[38]
Green–red ratio index	GRRI = G/R	[44]
Vegetativen	VEG = G/(R^a * B^{(1 − a)}) a = 0.667	[45]
Modified green blue vegetation index	MGRVI = (G² − R²)/(G² + R²)	[14]
MS-VIs
Normalized difference spectral index	NDSI = (R_λ1 − R_λ2)/(R_λ1 + R_λ2)	[46]
Simple ratio index	SR = R_λ1/R_λ2	[47]
Modified normalized difference spectral index	MNDSI = (R_λ1 − R_λ2)/(R_λ1 − R_λ3)	[48]

R, G and B are the reflectance of Red, Blue and Green channels, respectively. R_λ1 represents the reflectance of a variable band in the spectral region of 600–1000 nm. For an example, the NDSI_{(796, 679)} is calculated based on the reflectance data at λ₁ = 796 nm and λ₂ = 679 nm

ISSN: 1746-4811