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