Table 3.
Validation results for iron-related alteration zones using Sentinel-2 band ratio expressions.
| Alteration type | Band ratio expr. | Threshold | GMM pixels | Band-mask pixels | TP (Overlap) | FP | FN | TN (N = 11571) | Precision (%) | Recall (%) | IoU (%) | F1 (%) | Overall Accuracy (%) | 95% CI |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ferric iron (Fe³⁺) | 4 / 3 | 1.15 | 3051 | 3100 | 2986 | 65 | 114 | 8406 | 97.87 | 96.32 | 94.34 | 97.09 | 98.45 | [98.23–98.68] |
| Ferric Oxides | 11 / 8 | 1.13 | 1876 | 1900 | 1716 | 160 | 184 | 9511 | 91.47 | 90.32 | 83.30 | 90.89 | 97.03 | [96.72–97.34] |
| Ferrous iron (Fe²⁺) | 12/8 + 3/4 | 1.07 | 1387 | 1400 | 1251 | 136 | 149 | 10,035 | 90.19 | 89.36 | 81.45 | 89.77 | 97.54 | [97.25–97.82] |