## 3 Results  
### Accuracy Assessment with the Simulated Dataset  
The simulated test dataset described in Section 2.1.1 was employed to quantify the accuracy of the full-spectrum SIF retrieval algorithm, because the true values of the SIF were not available from the field measurements. Firstly, we analyzed the full-spectrum accuracy of the retrieved SIF using simulated test data with an SR of 0.3 nm and without noise. Figure 5a shows an example of a retrieved SIF spectrum (which has an average accuracy level) together with the true SIF spectrum from the test dataset. Figure 5b shows the full spectrum RRMSE of the 2304 retrieved SIF spectra in the test dataset. The average SIF spectrum and the central position of the three employed absorption bands are also plotted for reference. It can be seen that the retrieved and true SIF spectra fit very well. The RRMSE is less than 5% in the spectral region around 650-770 nm, which covers most of the SIF emission region, and is less than 14% within the full spectral region that we studied. The error is relatively small in the region of the three absorption  
Figure 4: The variation in the average RRMSE in the SIF retrieved from the 2304 test datasets against the number of iterations. bands that were used to estimate the weighting coefficients of the PCs of the SIF by least-squares fitting. The results, therefore, indicate that the F-SFM algorithm is quite accurate for full-spectrum SIF retrieval. The ratio of the fluorescence spectrum peaks (SIF\({}_{735}\)/SIF\({}_{685}\)) is an important shape parameter in numerous applications (reviewed by [PERSON] _et al._[20]). For example, it has been proved that this ratio is related to the physiological status of vegetation in terms of things such as the chlorophyll content [21] and the energy exchange process between PS I and PS II [19]. Therefore, we analyzed the accuracy of the value of SIF\({}_{735}\)/SIF\({}_{685}\) retrieved by the proposed F-SFM algorithm. Figure 6 shows the correlation between the true values of SIF\({}_{735}\)/SIF\({}_{685}\) from the test dataset simulated by SCOPE and those retrieved by F-SFM for an SR of 0.3 nm and without noise. The points are located near to the 1:1 line with an R\({}^{2}\) of 0.98 and an RRMSE of 3.56%, which represents a satisfactory accuracy for the retrieved value of  
Figure 5: (**a**) An example of a retrieved reflectance spectrum (black dashed line) together with the true reflectance spectrum from the test dataset (solid gray line); (**b**) An example of a retrieved SIF spectrum (dashed black line) together with the true SIF spectrum from the test dataset (solid gray line); (**c**) The full spectral RRMSE of the 2304 retrieved SIF spectra in the test dataset (black) together with the mean SIF spectrum (gray). These results were derived from data with an SR of 0.3 nm and without noise. The dashed vertical lines show the central position of the three absorption bands. Figure 6: The correlation between the true values of SIF\({}_{735}\)/SIF\({}_{685}\) and those retrieved from the simulated test dataset (2304 samples with SR of 0.3 nm and without noise). SIF\({}_{735}\)/SIF\({}_{685}\). These results show that it is feasible to estimate the spectral characteristics of SIF (intensity and shape information) based on the proposed full-spectrum SIF retrieval method. Secondly, we tested the accuracy of the algorithm using simulated data with different SRs and SNRs. Contour maps were employed to illustrate how the variation in the full-spectrum RRMSEs in the retrieved SIF depends on the change in SR (for the range 0.3\(-\)3 nm) and SNR (for the range 300\(-\)10,000) (Figure 7). The RRMSE contours show that the full-spectrum SIF retrieval method is not very sensitive to the SR. The sensitivity to SNR increases with a decrease in SR because the absorption depth is small for a low SR and the relative intensity of the SIF is low. When both the SR and SNR are relatively low (3 nm and 300, respectively), the full-spectrum RRMSE is still less than 30%.