# Space-Based Displacement Monitoring of Coastal Urban Areas: The Case of Limassol's Coastal Front
## 4 Discussion  
In this study, the first assessment of land subsidence on the Limassol coastal front using Copernicus Sentinel-1 mission data from 2017 to 2021, open software toolboxes, and the leveling technique for the comparison and validation of SAR results is rigorously presented. As illustrated in the Results section, newly built structures affect the Limassol coastal front by subsidence and uplift, ranging from almost \(-5\) mm to 5 mm [Figures 9 and 10]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Name**} & **Mean Displacement** & **Mean Displacement** & **Vertical** \\  & **Rates by PSI** & **Rates by Leveling** & **Displacement** \\  & **Analysis from 2017** & **from 2017** & **Difference from 2017** \\  & **to 2021 (mm)** & **to 2021 (mm)** & **to 2021 (mm)** \\ \hline The One & \(-2.68\) & \(-2.500\) & \(-0.18\) \\ \hline Trilogy & \(-2.76\) & \(-2.500\) & \(-0.26\) \\ \hline The Dream Tower & \(-0.48\) & \(-0.102\) & \(-0.291\) \\ \hline Limassol Del Mar & \(-1.44\) & \(-5.003\) & \(-3.563\) \\ \hline The Icon & \(1.16\) & \(2.01\) & \(0.85\) \\ \hline Sky Tower & \(0.36\) & \(0.043\) & \(0.382\) \\ \hline Olympic Residence & \(-3.48\) & \(-3.000\) & \(-0.48\) \\ \hline The Oval & \(-1.48\) & \(-1.238\) & \(-1.439\) \\ \hline iHome & \(-0.84\) & \(-0.484\) & \(-0.662\) \\ \hline DTA Tower & \(-0.054\) & \(-1.901\) & \(-1.847\) \\ \hline Arc Ship Tower & \(-1.68\) & \(-1.290\) & \(-1.485\) \\ \hline MARR Tower & \(0.080\) & \(2.090\) & \(1.010\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Final land subsidence results for Limassol coastal front according to PSI and leveling techniques. Figure 10: Land subsidence on Limassol coastal front using the IDW interpolation. Figure 9: Legend of the colors used as presented in the final map of results. subsidence were presented in the Olympic Residence two-building complex at \(-4.906\) mm over five years. Beyond that, subsidence-affected buildings included the Dream Tower, Limassol Del Mar, the Oval, iHome, DTA Tower, and Arc Ship Tower. Contrarily, in some cases, it can be noticed that uplift happens. Those areas are the ICON, Sky Tower, and MARR Tower. Although uplift values were rated as almost zero millimeters over a period five years, the cause of the specific change shall be identified. Concerning being in an area reclaimed from the sea, the deformations may be due to ground settlement taking place in the filler materials under the surface. Positive accumulated ground motion trends can also be shown as relative movements towards the satellite. Of note is that when studying the behavior of displacements in the environment surrounding artificial objects, it is advisable to explore the whole area. For example, land subsidence on the Limassol coastal front could be looked at regionally instead of buildings as a unit. In that case, it can be clearly seen that the area where those buildings are constructed is affected the most. Furthermore, especially in the Molos area of Limassol, in the west part of the studied area, there are places in which the land subsidence is equal to \(-5\) mm/year. Generally analyzing each location in the coastal plain, it can be deduced that except for the new massive development, the erosion of the coastal plain, which is caused by various factors, should be studied. Various types of land subsidence may occur in the Limassol coastal front, namely subsidence due to groundwater extraction, the mean sea level rise, subsidence induced by the load of the constructions, and geotechnique subsidence caused by the alluvium soil. Additionally, it is possible to highlight the presence of new construction sites created in the area of interest. Finally, due to the recent construction dates, further research in the study area could be directed to applying new combinations of technologies and methodologies. Although leveling is a time-consuming procedure, additional leveling benchmarks could be installed to add density to the current height network, with every benchmark corresponding to one building.