Statistic | Formula | Range | Best value | Conditioning |
Coefficient of determination |
| 0 to 1 | 1 | Describes the proportion of variance in the in situ data that are accounted for by the satellite data the closer to 1 the better [30] . |
RMSE-Observation standard deviation ratio |
| 0 to ∞ | 0 | A low RSR is directly proportional to the Root Mean Square Error (RMSE). The closer it is to zero the better [31] . |
Nash-Sutcliffe efficiency coefficient |
| −∞ to 1 | 1 | The normalized statistic determines the relative magnitude of the residual variance of the satellite observation in comparison to the in situ measured variance [31] . The closer the value is to 1 the better. |
Bias percentage |
| −∞ to ∞ | 0 | Measures the average tendency of satellite models to be smaller or larger than the in situ measurement [32] . Low values close to zero (0) indicate accurate simulation of the satellite data, positive values indicate underestimation while negative values indicate overestimation [31] . |