## 4 Results
### Cross-Sensor Comparison of Water Quality Products  
The multitemporal TSM maps derived from PRISMA, synthesized Sentinel-2, and Sentinel-2 images are shown in Figure 6. The visual inspection of the maps conveys an intuitively good agreement among the associated TSM maps. Note that the retrievals for 23 April 2020 exhibit higher values of TSM compared to the other dates and the maps for this date are shown with a different color bar to  
Figure 4: \(R_{rs}\) spectra for the stations St1 (**a**) and St2 (**b**) in Lake Trasimeno based on PRISMA and Sentinel-2 acquisitions on 23 April 2020. Figure 5: Cross-sensor agreement analyses between the \(R_{rs}\) data derived from PRISMA (resampled to Sentinel-2 bands) and Sentinel-2 (acquired on 23 April 2020). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & **442 nm** & **492 nm** & **559 nm** & **664 nm** & **704 nm** & **740 nm** & **781 nm** & **864 nm** \\ \hline
**R** & 0.83 & 0.84 & 0.91 & 0.89 & 0.90 & 0.88 & 0.87 & 0.88 \\ \hline
**RMSD (sr\({}^{-1}\))** & \(4\times 10^{-3}\) & \(7\times 10^{-3}\) & \(10^{-3}\) & \(2\times 10^{-3}\) & \(10^{-3}\) & \(6\times 10^{-3}\) & \(8\times 10^{-3}\) & \(4\times 10^{-3}\) \\ \hline
**MAD** & 1.51 & 1.53 & 1.04 & 1.13 & 1.09 & 1.18 & 1.19 & 1.42 \\ \hline
**Bias** & 1.51 & 1.53 & 1.03 & 1.12 & 1.06 & 0.96 & 1.13 & 0.83 \\ \hline \end{tabular}
\end{table} 
Table 3: The agreement statistics for the cross-sensor comparison of \(R_{rs}\) at different wavelengths derived from PRISMA and Sentinel-2 data. enhance the visualization. Figures 7 and 8 illustrate the retrievals of Chl-a and CDOM derived from the same images, respectively. The corresponding maps derived from PRISMA, synthesized Sentinel-2, and Sentinel-2 are in good agreement but with a lower degree compared to those of TSM. Figure 6: Multitemporal total suspended matter (TSM) maps derived from PRISMA, synthesized Sentinel-2 (PRISMA resampled), and Sentinel-2 images. The missing data are related to the cloud cover. Figure 7: Multitemporal Chl-a maps derived from PRISMA, synthesized Sentinel-2 (PRISMA resampled), and Sentinel-2 images. The missing data are related to the cloud cover. Distribution of the retrieved constituents is investigated using boxplots in Figure 9. The bottom and top edges of boxes indicate the 25 th and 75 th percentiles whereas the central line and dot symbols show the median and average values, respectively. The extreme values are represented by the extensions of the boxes. These statistical indications further confirm a good cross-sensor agreement among the retrievals, particularly for TSM. The plots in Figure 9 indicate a quite high variability of the constituents over time. For instance, the PRISMA-derived average concentration of TSM on 23 April 2020 is about 2.6 times of that retrieved for 3 June 2020 (16.4 g/m\({}^{3}\) vs. 6.2 g/m\({}^{3}\)). The multitemporal average values of TSM, Chl-a, and CDOM derived from PRISMA images are on the order of 9.1 g/m\({}^{3}\), 4.9 mg/m\({}^{3}\), and 0.34 m\({}^{-1}\), respectively. The agreements of the retrieved constituents are further examined by regressing the values extracted from the maps against each other (described in Section 3.3). The image-based matchup analyses are shown for TSM retrievals in Figure 10.  
Figure 8: Multitemporal CDOM maps derived from PRISMA, synthesized Sentinel-2 (PRISMA resampled), and Sentinel-2 images. Figure 10: Agreement analyses among the TSM derived from PRISMA, synthesized Sentinel-2 (PRISMA resampled), and Sentinel-2 images in terms of R and RMSD. Figure 9: Distribution of the retrieved constituents (TSM, Chl-a, and CDOM) from PRISMA, synthesized Sentinel-2 (PRISMA resampled), and Sentinel-2 images.