## 3 Results
### Testing of the Field-Measured Data  
Although the values of the vegetation parameters were set to be different, the training and test datasets were simulated by the same model. As it is a statistically based method, it was necessary to test the applicability of the proposed F-SFM method with real observations. Therefore, the field experiment datasets obtained using the QE Pro and ASD FieldSpec4 spectrometers were used for further testing.  
Figure 9 shows the full-spectrum SIF retrieved from the diurnal field measurements made by QE Pro on 25 April 2015 at intervals of one hour. The results show that the double-peak characteristic of the SIF spectrum has been successfully reconstructed; the diurnal variation trend in the SIF is also reasonable and consistent with the results from literature (e.g. [40, 41, 42]).  
As the true values of the SIF were not available in the field data, it was not possible to assess the accuracy of the retrieved full-spectrum SIF directly using the field-measured dataset. It was only possible to estimate the accuracy of F-SFM using the SIF values retrieved at some specific absorption wavelengths with the FLD-based method. As described before, the commonly used 3 FLD method is fairly reliable for SIF retrieval at the O\({}_{2}\)-A and O\({}_{2}\)-B bands if the configuration of the QE Pro Spectrometer (RRMSE \(<\) 25%) is used. Therefore, the SIF retrieved by the 3 FLD method at the O\({}_{2}\)-A and O\({}_{2}\)-B bands was employed as a reference to estimate the reliability of the proposed F-SFM algorithm. Taking the SIF retrieved by 3 FLD from the dataset obtained by the QE Pro as a reference, we analyzed  
Figure 8: Contours of the RRMSE (%) in the SIF at the O\({}_{2}\)-A (**a–c**) and O\({}_{2}\)-B (**d–f**) bands retrieved by the 3 FLD (**left**), iFLD (**middle**) and F-SFM (**right**) algorithms using simulated test datasets with different SRs and SNRs.  
the accuracy of the SIF retrieved by F-SFM from the datasets obtained by both the QE Pro and ASD FieldSpec4 (Figure 10). For the data obtained by the QE Pro, most of the points are located near the 1:1 line with an R\({}^{2}\) of 0.97 and RRMSE of 12.6% for the O\({}_{2}\)-A band and an R\({}^{2}\) of 0.92 and RRMSE of 15.4% for the O\({}_{2}\)-B band, which indicates that the values of SIF retrieved by the two methods match well. For the data obtained by the ASD FieldSpec4, the points are still distributed around the 1:1 line but the correlation is somewhat weaker (R\({}^{2}\) of 0.88 and 0.66 and RRMSE of 18.7% and 29.4% for the O\({}_{2}\)-A and O\({}_{2}\)-B bands, respectively). The SNRs of both the QE Pro and ASD FieldSpec4 are sufficient (higher than 1000) for the F-SFM algorithm, so the much higher SR of the QE Pro (0.3 nm _vs._ 3 nm) leads to more accurate SIF retrieval, especially for the O\({}_{2}\)-B band.  
In addition, we also compared the retrieved peak-value ratios (SIF\({}_{735}\)/SIF\({}_{685}\)) for the data obtained by the QE Pro and ASD FieldSpec4, as shown in Figure 11. The points are located around the 1:1 line with an R\({}^{2}\) of 0.71. These results show that the F-SFM algorithm is not very sensitive to the SR and can be applied to data obtained by spectrometers whose SR is relatively low, such as the popular  
Figure 10: Comparison between the SIF retrieved by 3 FLD using data obtained by the QE Pro and the SIF retrieved by F-SFM using data obtained by the QE Pro (blue points) or ASD FieldSpec4 (green triangles). The graphs shown are for the SIF at the O\({}_{2}\)-A (**a**) and O\({}_{2}\)-B (**b**) bands.  
Figure 9: The full-spectrum SIF retrieved from the diurnal field measurements made by the QE Pro on 25 April, 2015. For clarity, only measurements made on the hour from 9:00 to 17: 00 are plotted.