3.2.2. Evaluation of SOS Dates

The SOS detected from the five VIs were compared pixel-by-pixel via scatterplots on each pair of image combinations. Three indicators, the correlation coefficient (R), the mean absolute error (MAE), and the root mean square error (RMSE), were calculated to evaluate the consistency between the SOS detected from different VIs. Then, considering the influence of elevation on the SOS, the study area was divided into four elevation zones, including < 3500 m, 3500–4000 m, 4000–4500 m, and ≥ 4500 m. The changes in the detected

SOS dates with varying elevations were analyzed through zonal statistics. The effect of snow on the detected SOS was further analyzed in each elevation zone.
