## 5 Conclusions  
The authors adapted the parametric method with conditional equations to align GNSS observations during mobile surveys. The theoretical assumptions of the method were verified using the data from GNSS satellite surveys during the inventory of the railway route of Tczew-Chojnice-Brusy-Chojnice-Tczew in northern Poland.  
The 246-km-long test section is located in areas with varying satellite system signal availability (open areas, forest areas and built-up areas). This enabled the suitability of the method to be  
Figure 8: The route of railway surveys with aligned 2D coordinates.  
Figure 9: Sections of the railway route: (**a**)—near the locality of Czarna Woda, (**b**)—in an urbanised area in the town of Tczew.  
checked by aligning the observations obtained from GNSS records, which, due to the occurrence of various field-obscuring features, were characterised by different levels of accuracy and availability of GNSS signal.  
The application of the surveying aligning method for satellite observations supported additionally with tacheometric surveys of the position of GNSS receiver antennas on the mobile surveying platform finally enabled the accuracy of the determinations of the antenna position coordinates to be increased and the internally consistent surveying structure to be correctly fitted within the area of measurement performance.  
Analysis of the accuracy levels for the final determinations of the antennas' position coordinates demonstrated that the parametric method with conditional equations can be applied in research tasks in which the subject of the study is the internally consistent surveying structure and the obtained observations about the positions of these structures are additionally supported with highly accurate surveys inside the structure under analysis.  
The research results described in this article are the next step in checking the suitability of the LSce method in rail transport. Earlier, the authors checked its usefulness on tram tracks [48]. Moreover, the use of the mobile measurement platform is described, for example, in [18; 19; 20; 21]. Previous studies indicate the repeatability of the results and an increase the accuracy of determinations of the position of GNSS receivers' coordinates.  
To confirm the possibility for the use of a mobile surveying platform, the authors are preparing to conduct subsequent surveying campaigns on various test sections under different conditions of GNSS signal availability. However, to confirm the universality of the proposed adaptation of the alignment method, testing should be conducted using other vehicles. It will then be possible to fully assess the suitability of the technologies applied and the methods developed for various forms of transport.  
Conceptualization: K.C., C.S., Z.W., A.W., W.K.; Visualization: B.C., P.D., K.C.; Formal analysis: C.S., Investigation: K.C., C.S., A.W., W.K., K.K., J.S. ([PERSON]), P.D., M.S., P.C., J.S. ([PERSON]), S.J., S.G., R.L., Writing--original draft preparation: K.C., Z.W., B.C.; All authors have read and agreed to the published version of the manuscript.  
The results of the research work presented in this article are a summary of one of the research stages being carried out as part of the research project No POIR.04.01.01-00-0017/17 entitled \"Development of an innovative method for determining the precise trajectory of a railborne vehicle\" by a consortium of the Gdansk University of Technology and the Gdynia Maritime University. The study was funded by the National Centre for Research and Development (_Narodowe Centrum Badan i Rozwoju_, NCBiR) and PKP Polskie Linie Kolejowe S.A.  
The authors declare no conflict of interest.