## 5 Conclusions  
This study compares two approaches to integrating leveling and GNSS data for the relative study of vertical movements of the Earth's crust. Theoretical approaches were tested using transformation and hybrid network adjustment. The results can be summarized as follows:  
* The smallest unit error m\({}_{0}\) (0.27 mm/yr (version 1) and 0.11 mm/yr (version 2)) and transformation error m\({}_{t}\) (0.45 mm/yr (version 1), 0.15 mm/yr (version 2)) are 3x smaller for the affine transformation compared to the other transformations. * An error distribution close to the normal distribution was obtained for the hybrid network adjustment version 2. * The average error after adjustment of the hybrid network in both versions is 0.1 mm/yr. * The smallest differences in vertical movement between affine transformation and hybrid network adjustment were obtained for version 2: 0.91 mm/yr. * The use of the Hausbrandt correction does not significantly improve the transformation results. The results obtained show that both methods are suitable for the above purpose. Integration using the hybrid network adjustment method is more difficult to auto  
Figure 14: Relative vertical movements from four variants (source: own study). mate than transformation. Each new point in the network generates a change in its structure and properties. Of the transformation methods, the smallest errors were obtained for the 12-parameter affine transformation. Therefore, it is recommended to use this transformation. The results of this work can be used to develop terrain deformation models from hybrid data over any size of area. There is no need to create artificial links between GNSS stations and carry out time-consuming adjustment of the hybrid network. The same effect is obtained using an affine transformation. It has been proven that the use of the transformation allows for the transition from an absolute reference to a relative reference, which is one of the main problems when combining leveling and GNSS data for vertical crustal variations. The largest differences in vertical movements in all tested variants were at the adjustment points. These points were identified as having intrinsic or unrelated crustal motions. In both the adjustment and transformation of the hybrid network, local vertical motions in excess of regional motions are canceled out. Not all common points in the hybrid network are suitable as connecting points. The selection of joint points in adjustment as well as adjustment points in transformation should be controlled and outlier points should be verified geologically and tectonically. Scale-free network theory has been shown to be suitable for verifying the utility and location of connection points in a hybrid network. The typing of connection points using scale-free network theory makes it possible to identify the connection points of greatest importance in the network. The same connection points can be used in hybrid network adjustment, as well as transformation. It has been confirmed that not all possible connection points in the hybrid network should be adopted for transformation or adjustment (they must be relevant in the network). The area of Poland shows little vertical movement. The isolines are strongly influenced by local underground mining and the pressure of urban agglomerations on the Earth's crust. GNSS stations are subject to vertical movements caused by local factors; therefore, it is necessary to analyze the geological location of stations, especially those adopted as adjustment points. Once the model of vertical movements from hybrid data is developed, geodynamic correction is also necessary. The proposed approach can be extended with new data, e.g., vertical movements from SAR, SLA--Sea Level Anomaly, gravimetry. SAR data are available through the Copernicus Land Monitoring Service as the European Ground Motion Service (EGMS). It can be used, among other things, to verify the location of permanent GNSS stations and to correct the model of vertical movements of the Earth's crust.