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Table 3 The calculation method and reference of spectral index related to crop moisture status

From: Comparison of new hyperspectral index and machine learning models for prediction of winter wheat leaf water content

Spectral index Definition or equation References
Ratio Index R1650/R2220 Elvidge et al. [18]
Normalized differential water index, NDWI (R860−1240)/(R820 + 1240) Gao et al. [19]
Moisture stress index, MSI R1600/R820 Hunt et al. [20]
Maximum water difference index, MDWI (Rmax1500−1750)-(Rmin1500−1750)/(Rmax1500−1750) + (Rmin1500−1750) Eitel et al. [21]
Hyperspectral normalized difference vegetation index, hNDVI (R900−R680)/(R900−R680) Rouse et al. [22]
Water index, WI R900/R970 Penuelas et al. [23]
Simple ratio water index, SRWI R820/R1200 Zarco-Tejada et al. [24]
Normalized Difference Infrared Index, NDII (R820−R1649)/(R820 + R1679) Hardisky et al. [25]
WI/hNDVI (R900/R970)/[(R900−R680)/(R900−R680)] Zhang et al. [8]
FD730-955 FD730/FD955 Liang et al. [26]