Table 2.
Indexes and formulas derived from reflectance information.
| Reflectance index* | Formula** | References | |
|---|---|---|---|
| NDVI | Normalized Vegetation Index | ((R(900 nm)−R(680 nm))/(R(900 nm)+R(680 nm)) | Rouse et al., 1973 |
| SR | Simple Ratio | (R(900 nm)−(R(680 nm)) | Jordan, 1969 |
| RNDVI | Normalized Difference Vegetation Index | (R(900 nm)−R(680 nm))/(R(900 nm)+R(680 nm)) | Raun et al., 2001 |
| PRI | Photochemical Reflectance Index | (R(531 nm)−R(570 nm))/(R(531 nm)+R(570 nm)) | Penuelas et al., 1997 |
| PSSRa | Pigment-Specific Simple Ratio of Chl-a | (R(800 nm))/(R(680 nm)) | Blackburn, 1999 |
| WI | Reflectance Water Index | (R(900 nm))/(R(970 nm)) | Penuelas et al., 1993 |
| NWI1 | Normalized Water Index 1 | (R(970 nm)−(900 nm))/(R(970 nm)+R(900 nm)) | Babar et al., 2006b; Prasad et al., 2007 |
| NWI2 | Normalized Water Index 2 | (R(970nm)−R(850nm))/(R(970nm)+R(850nm)) | |
| NWI3 | Normalized Water Index 3 | (R(970 nm)−R(920 nm))/(R(970 nm)+R(920 nm)) | |
| NWI4 | Normalized Water Index 4 | (R(970 nm)−R(880 nm))/(R(970 nm)+R(880 nm)) | |
| ONI | Oryza N Index | (R(810 nm))/(R(560 nm)) | Xue et al., 2004 |
| DZNI | Dry Zea N Index | (R(575 nm))/(R(526 nm)) | Zhao et al., 2003 |
The spectral region used ranged between 526 and 970 nm. Chlorophyll's electromagnetic absorption range is between 400 and 500 nm, and from 600 to 700 nm.
*
Reflectance indexes taken from Bowman et al. (2015).
**
R represents the reflectance measured at a particular wavelength.