## 5 Discussion
Table 1 also reports the average RMSE values calculated over the areas of Lingang New City in its western (WS) and eastern (ES) sectors, respectively, as retrieved from the combined ASAR/ENVISAT and CSK (vertical) deformation time-series. In addition, we repeated the RMSE calculation by separately considering the fitting of the obtained models and the ASAR/ENVISAT and CSK time-series. The achieved results are also summarized in Table 1.  
We note that the best-fit models retrieved as the result of the combination of C/X-band displacement time-series are in general agreement with the forecast models studied in our previous investigation [19], which were exclusively based on the use of ASAR/ENVISAT data. Moreover, it is worth noting that the new CSK deformation time-series distinctly show that the rate of deformation in ocean-reclaimed platforms has been progressively decreasing over the most recent six years, which is in general accordance with the time-dependency of the models in Equation (5). This is also confirmed by the temporal shape of the individual ASAR/ENVISAT and the CSK time-series, as well as by the plots of the combined (vertical) deformation time-series. In particular, Figure 5 shows the deformation time-series relevant to the four selected pixels, labeled as P\({}_{1}\), P\({}_{2}\), P\({}_{3}\), and P\({}_{4}\). Table 2 lists the best-fit model parameters retrieved for these four selected points. We note that these pixels have been selected among the ones characterized by the smallest RMSE values (which are indicated for all the four pixels in the plots of Figure 5) as being representative of the (average) present-state of residual settlements in the different zones of Lingang New City. As shown in previous investigations, it is clear that the eastern part of the city is still (in 2016) affected by appreciable deformations. Conversely, the western sector of the city is, at present, ten years after the end of the reclamation processes [19], almost stable. One of the outcomes of our previous investigation was the recovery of some preliminary predictions of the cumulative displacements in the ocean-reclaimed platforms of Shanghai by the end of 2015, 2020, and 2025 (see Figure 8 of [19]), calculated by considering the end of reclamation procedures as the starting time for the soil consolidation phase. Finally, we also estimated the deviation between the (average) measured and modeled deformation rates for both the ES and WS of the city in the 2007-2010 and 2014-2016 observation periods, respectively. The achieved results are summarized in Table 3. In the analysis, there is a perfect agreement between the measured and the modeled deformation (subsidence) rates in the 2007-2010 period. Conversely, in the 2014-2016 period, the agreement is perfect in the WS, whereas there is an average difference of about 3 mm/year in the ES. This finding is not surprising, being that the soil consolidation stages in the ES of the city have not yet concluded. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sensor** & **WS (mm)** & **ES (mm)** \\ \hline ENVISAT & 5.8 & 8.0 \\ CSK & 3.4 & 5.7 \\ ENVISAT/CSK & 4.8 & 7.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average root mean square error (RMSE) values between the DInSAR time-series and the recovered best-fit models for the western (WS) and the eastern (ES) sectors. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Point** & \(S\) **(cm)** & \(k\) & \(\lambda\) & \(\delta\) \\ \hline P1 & –19.7 & 11.9 & 0.7 & –5 \\ P2 & –41.2 & 26.6 & 0.7 & –3 \\ P3 & –27.6 & 16.2 & 0.7 & –1 \\ P4 & –11.4 & 8.6 & 0.5 & –4 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values of the best-fit model parameters retrieved for the four selected points of Figure 5b. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Period** & **Measured (mm/Year)** & **Modeled (mm/Year)** \\ \hline  & **WS** & **ES** & **WS** & **ES** \\ \hline
2007–2010 & –16.9 & –35.0 & –16.6 & –35.2 \\
2014–2016 & –3.9 & –16.9 & –3.4 & –13.4 \\ \hline \hline \end{tabular}
\end{table}