## 5 Discussion  
Only the integration of the city's geology, which benchmarks vertical movements in the levelling sequences of the first and second class, will allowed us to identify stable and unstable areas of Szczecin over the course of this century. This will enable the reliable monitoring of these areas in the future.  
Reference points for benchmarks showing significant values of vertical displacements in the area of Miedzyodrze are located on geologically stable formations, outside of this area. Their displacement over the last 30 years did not exceed tenths of mm. Therefore, it becomes possible to monitor deformations of engineering objects not only in the effectual  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Position**} & **Coordinate X** & **Coordinate X** & **Coordinate Y** & **Coordinate Y** & **Height H** & **Height H** \\  & **(Metre)** & **(Error Metre)** & **(Metre)** & **(Error Metre)** & **(Metre)** & **(Error Metre)** \\ \hline
1 & 5,914,268.521 & 0.0011 & 5,481,721.882 & 0.0012 & 18.615 & 0.0052 \\
2 & 5,913,766.879 & 0.0015 & 5,472,143.054 & 0.0010 & 5.709 & 0.0047 \\
3 & 5,915,137.456 & 0.0020 & 5,482,014.790 & 0.0012 & 14.133 & 0.0065 \\
4 & 5,921,687.950 & 0.0011 & 5,473,141.886 & 0.0007 & 6.304 & 0.0041 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Coordinates aligned with ASG-EUPOS stations of 3 h measurements (May 2021).  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Point**} & **Vertical Displacement \(\Delta H_{z}\) [mm]** & **Average Error** \\  & \(\pm m_{ABz}\) [mm]** \\ \hline
1 & 0 & 7.5 \\
2 & 0 & 6.9 \\
3 & 0 & 9.6 \\
4 & \(-19\) & 6.2 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Values of vertical displacements of benchmarks I and II segment of the system after the second survey in May 2021 at 3 h intervals.  
aspect, but also in the cause and effect one (monitoring the development of the deformation process during the planning phase, even before construction of the object).  
A complexity control and measurement system should be useful while monitoring surface and object deformation in areas built of sediments such as peat [15]. Economic considerations justified utilization of the measurements by GNSS [16], which could be corrected to high precision reference over much larger distances [17]. Potential investors of the planned objects can take these data into account while monitoring deformations [18,19]. Different degrees of peat decomposition result in different susceptibility to extrusion (displacement) of loaded layers; peats with medium and high degrees of decomposition according to the von Post scale are particularly susceptible to displacement [20]. Organic soils with varying physical characteristics, such as moisture content, porosity, liquid limit, and degree of plasticity, are prevailing in the researched area.  
While geological aspects are critical, the use of the alternative monitoring system based on InSAR data was not justified in terms of accuracy and precision merit. This is due to the fact that a loose layer of fertilized soil is present over more stiff organic geological structures. InSAR deals with the observation of surface changes of larger areas of terrain; the research carried out concerned displacements of closely adjacent benchmarks over long time intervals.