## 1 Introduction  
The city of Szczecin, Poland, was chosen for this research. It is a port city that plays an important role as a transport and communication center. It was designed to facilitate, and still serves, the development of a maritime economy.  
The conditions of the geological land structure are important here. Although the distance from the sea is approximately 60 km, the city serves as a high-ranking seaport. The crossing of waterways and inland roads favors the development of Szczecin as a large industrial center. The main industrial facilities close to the water areas are: shipyards; harbor berths; and harbor loading, storage, and administrative facilities. Examples of individual facilities include the Municipal Waste Sorting Plant and the Port Authority of Szczecin building (see Figure 1). Most of these constructions are located in the area of the Miedzydorze islands (Lasztownia, Grodzka, Ostrow Grabowski, and Ostrow Mielenski) (Figures 1 and 2).  
The implementation of an appropriate control and measurement system (Table 1) has been assumed as necessary for the reliable monitoring of deformation of the existing and planned engineering structures in the Szczecin area.  
Similar GNSS-based systems have been successfully implemented in 3D deformation studies of several significant engineering objects and geodynamic polygons [1, 2, 3]. Other systems used Interferometry Synthetic Aperture Radar (InSAR) [4, 5] or satellite altimetry to monitor regional vertical motions [6]. In [5], it was demonstrated that, through the use of an advanced InSAR technique (the APSIST(tm) Intermittent Small Baseline Subset technique), the near-complete coverage of ground motion measurements is possible, despite intermittent snow cover. However, the underlying geological structure was not taken into account in these systems, nor was the methodology used, causing the field work involved in an additional levelling survey to be labor-intensive, time-consuming, and expensive, with the final accuracy of measurements degraded.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Segment I** & **Segment II** \\ \hline Measurement method & GNSS, precision levelling & GNSS, precision levelling \\ \hline Frequency of observation & 1/year to 5/year & 2 months \\ \hline Accuracy of displacement determination & \(\pm\)(0.5–5) mm & \(\pm\)(0.5–5) mm \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristic of a control and measurement system for 3D space testing.  
Figure 1: The area of Szczecin Miedzyodrze and the location of Szczecin on a map of Poland.  
At the beginning of our research, stable reference points (benchmarks situated outside areas of the islands on geologically stable formations, such as sand) were localized in a 3D space as the as the first and second segment of the system (Figure 2. The analysis of the levelling lines of the 1 st and 2 nd class geodetic accuracy made it possible to select one more reference point for the 1 st segment of the control and measurement system (Figure 3). This made it possible to carry out observations of the surface movements of organic sediments of the Szczecin islands area in a 3D space [2] using GNSS satellite observations. Detailed recognition of geological structure [7] of subsoil in the vicinity of these points was helpful for the precise localization of stable reference benchmarks (1 and 3). Reports on the implementation of these works are included in Section 4 of this paper. The EcoGenerator was chosen as an example object to install a second segment of the control and measurement system.  
Figure 2: Geology of Szczecin area with benchmarks of first and second segment of control and measurement system.  
The innovation of research consisted of the integration of various observation techniques into one control and measurement system; the selection of the techniques and segments of the system depended on the geological structure of the subsoil in a given region.