## 5 Conclusions  
On four railway sections of different length (4.5 to 16.5 km), the achieved accuracy of GNSS measurements by RTK method was analyzed according to the procedure included in the RA M20/MP007 regulation, which is used in the operating conditions of the railway in the Czech Republic. Our research has led us to the following conclusions. 1. It was proved that the homogeneous accuracy in coordinate standard deviation was better than \(\sigma_{x,y}=5\) mm. 2. The fact that GNSS instrument with GPS, GLONASS, Galileo, BeiDou signals is commonly available nowadays simplifies the preparation and planning of observations by ensuring that enough determining satellites are available under normal operating conditions of par-tially obstructed horizon. 3. The accuracy achieved under operating conditions was further compared with the accuracy achieved by the same procedure under ideal conditions on a calibration base. The results show that the accuracy in operational conditions is two-three times worse due to the non-ideal observation conditions, i.e., horizon obstructions, surrounding vegetation and the effect of multipath. As a result, the influence of multipath can be reduced by repeated GNSS measurements with a time interval of optimally 3-4 h, and the mean value calculated from repeated measurements is closer to the conventionally true value. 4. When using GNSS equipment with a tilt sensor, the accuracy of the position determination will be degraded, and therefore this mode should not be used for accurate GNSS measurements of the primary track point system. For older GNSS equipment using an IMU unit in combination with a magnetic compass, there is a risk of a systematic bias of up to several tens of millimeters, which is measured when the antenna is rotated by 180\({}^{\circ}\). The use of GNSS with an IMU unit gives satisfactory results, and it is advisable to work with a 180\({}^{\circ}\) rotation of the instrument to improve the accuracy of the result. This is useful for geodetic points with limited access, where it is not possible to measure with levelled GNSS equipment. Changing the inclination can also influence the multipath effect to some extent. 5. The current uniform transformation key, in force since 2018, has residual geometric inhomogeneities (from 90% to 10 mm/km, sporadically up to 20 mm/km) that metrologically degrade the calculation results of the terrestrially measured secondary system inserted into the GNSS measured primary system. On the whole, however, the method of determining the primary system by GNSS technology in combination with the terrestrially determined secondary system provides good homogeneity and sustainability of accuracy for the needs of construction and maintenance of railway lines, including high-speed lines. Achievement of high accuracy allows for easier analysis of inhomogeneities of the railway point field caused by their instability due to the necessity of their location in the vicinity of the operating track, and thus ensures long-term sustainability of repeatable accuracy of determination of geometric parameters regarding the center of the track. Our research will continue in the operating conditions of electrified lines. On electrified railway lines, the geodetic points of the primary system are placed on the column footings of traction poles, which increases the risk of multipath effects. **Author Contributions:** Conceptualization, J.B. and D.B. ; methodology, J.B.; validation, O.V. and L.B. ; investigation, L.B. ; resources, O.V. ; writing--original draft preparation, O.V. and J.B.; writing--review and editing, D.B. ; supervision, R.H.; project administration, R.H.; funding acquisition, O.V. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Brno University of Technology, specific research project Nr. FAST-J24-8598 \"Research into the Use of Progressive Geodata Collection Technologies and their Compatibility between CAD, GIS, BIM and DTM in the Digitalization of Construction Live Cycle\".