Table 8.
Validation results for the strongest performing models for water and nitrogen prediction across the different pre-processing and regression methods trialled- PLSR in combination with raw input data. Wavelength selection using the regression coefficient method produced the strongest models.
| VNIR | Full spectra (VNIR+SWIR) |
Wavelength selection regression coefficients | Wavelength selection feature positions | ||
|---|---|---|---|---|---|
| Water | R2 | 0.56 | 0.63 | 0.69 | 0.64 |
| RMSE | 2.85 | 2.81 | 2.53 | 2.74 | |
| RPD | 1.50 | 1.64 | 1.78 | 1.76 | |
| Nitrogen | R2 | 0.57 | 0.60 | 0.66 | 0.52 |
| RMSE | 0.42 | 0.43 | 0.41 | 0.47 | |
| RPD | 1.53 | 1.54 | 1.66 | 1.39 | |