# Assessment of GNSS Galileo Contribution to the Modernization of CROPOS's Services
## 5 Conclusions  
The modernization of CROPOS carried out in 2019 has enabled the inclusion of Galileo and BeiDou observation data into a networked solution. The performance of CROPOS prior the modernization was already at a high level; therefore, a significant improvement in terms of accuracy has not been achieved. The declared accuracy of CROPOS VPPS service of 2 cm (2D) and 4 cm (3D) has not been changed. The improvement in CROPOS's modernization can be seen through the increased availability and reliability of solutions. The number of available satellites has increased from 54 (31 GPS + 23 GLO) to 126 (31 GPS + 23 GLO + 22 GAL + 50 BDS) (July 2020). Although the GAL system has not yet reached its FOC, when it is able to provide an independent VPPS solution (GAL-only), that solution can be obtained with the declared accuracy of CROPOS VPPS. Several facts (circumstances) must be pointed out to correctly assess the results: the test was performed leveraging the potential of a sophisticated and almost brand-new model of GNSS receiver (Trimble R12), the station had an almost free horizon with a weak or even absent source of multipath, and, equally important, the measurements were performed strictly according to the provisions of the regulations for the basic work performance. Considering the results of VPPS positioning based on GAL-only observations, the greatest deviation from the daily solution was 15 mm (vertical component), which was within the declared accuracy level. Since the Galileo constellation is still not fully deployed, there are time windows with less than four visible satellites preventing the kinematic fixed solution in real-time. Considering the individual static solutions based on GGGB and GAL-only observations, it has been shown that GAL-only solutions showed a slightly greater spread (6 mm) in comparison to a GGGB solution (5 mm). The same can be stated for the results obtained with VPPS (GGG) and VPPS (GAL-only) results: all GAL-only results are within the radius of 7 mm, and all GGG results are within the radius of 6 mm from the REFERENCE. It has been demonstrated that taking redundant measurements (observation sessions) and averaging the results lead to accuracy and reliability improvement. By the declaration of FOC in the times to come, it is expected that the Galileo constellation will provide additional benefits and robustness to CROPOS as a system and to the performance of its services, as well. It must be pointed out that the study presented in this article has been carried out using a Trimble GNSS receiver which was supposed to work the best within a CROPOS network relying on Trimble's infrastructure. Further tests with GNSS receivers from other manufacturers will be carried out in the next period.  
Conceptualization, D.S. and A.K.; methodology, D.S. and Z.B.; validation, D.S., A.K., Z.B., and Z.N.; formal analysis, D.S., A.K., and Z.B.; investigation, D.S.; resources, D.S., data curation, D.S. and A.K.; writing--original draft preparation, D.S.; writing--review and editing, A.K., Z.B., and Z.N.; visualization, D.S. and Z.N.; supervision, Z.B. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The company Geomatika-Smolcak and its director [PERSON] are kindly acknowledged for allowing access to the GNSS receiver Trimble R12 and the associated equipment, thus enabling the field measurements and data collection. The State Geodetic Administration (SGA) of the Republic of Croatia is acknowledged for providing access to the VPPS and GPPS services of CROPOS. We would like to express our gratitude to three anonymous reviewers for their comments and suggestions which have contributed to the improvement of the manuscript.  
The authors declare no conflict of interest.