# A New Model of Quasigeoid for the Baltic Sea Area
## 6 Conclusions  
The computation of a regional gravimetric geoid model with proper accuracy is a difficult task that needs special notice and full investigation in all the phases of computations to produce good results.  
Using this high-quality data set, we have carried out the gravimetric quasigeoid computation using the Helmert condensation method. This procedure is shown as an efficient method to compute in high resolution the new quasigeoid in the area \(52^{\circ}<\lambda<68^{\circ}\) and \(11^{\circ}<\phi<30^{\circ}\) in a grid \(1.5^{\prime}\times 3.0^{\prime}\). Three versions of zero-tide quasigeoid were computed from the gravity data described above and geopotential models: GOCO06, GOCE-DIR6, and EIGEN-6C4.  
Twenty-nine GNSS/leveling points of the ASG-EUPOS network were chosen for evaluating the quasigeoid models. According to the analyses carried out, their accuracy is on the level of \(\pm 4\) cm. For reasons beyond our control, we have access to GNSS/leveling points at the southern end of the tested area, so we suspect that the accuracy of the calculated quasigeoid should be slightly higher about \(\pm 2\) cm.  
The gravity data used in this calculation come from different sources and differ in measurement methods, accuracy, and resolution. In addition, these data refer to different systems, both horizontal and vertical. We also did not have accurate information on gravity data tidal systems and terrain corrections (except in Finland, Sweden, and Poland) introduced into gravity anomalies. It is assumed that these data produced in the last century are in the mean tidal system and contain terrain corrections. Therefore, to calculate the new quasigeoid model in the Baltic, it is necessary to improve the quality of gravity data.  
This work uses data only from airborne measurements and measurements at sea performed between 1978 and 1980 by the teams of the Moscow Research Institute. Therefore, the impact of additional data, e.g., sea data from Hakon Mossby or altimetric data on the accuracy of the quasigeoids to be calculated, should be investigated.  
Finally, quasigeoid separation at the Wladyslawowo, Rozewie, and Ustka tide gauge stations was calculated. Differences between each geopotential model are from few mil  
Figure 11: Height anomalies calculated from different geopotential models at tide gauge stations in Wladyslawowo Rozewie and Ustka.  
limeters to 1 centimeter. Then, the mean quasigeoid separations at tide gauge stations were compared with the value obtained in the paper [46], p. 83. Due to different methods in quasigeoid computations and different data sets used, the observed shift of 5 cm means a good agreement between these two solutions.  
Conceptualization, J.N.; methodology, A.L.; software, A.L.; validation, A.L.; formal analysis, A.L.; investigation, A.L.; resources, A.L.; data curation, A.L.; writing--original draft preparation, A.L.; writing--review and editing, M.B.; visualization, A.L.; supervision, J.B.Z.; funding acquisition, J.B.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Geodetic SAR for Baltic Height System Unification and Baltic Sea Level Research Contract No. 4000126830/19/I-BG for ESA Project BALTIC+ THEMe No. 5 - Geodetic SAR for Baltic Height.  
The authors express their thanks to all institutions that have made gravity data available, namely, Bureau Gravimetrique International for the data from Sweden, Institute of Geodesy and Cartography in Warsaw, GETECH Company, Finnish Geodetic Institute, and Kort and Matrikelstyrelsen in Denmark. In addition, the authors are grateful to [PERSON] for the availability of the GRAVSOFT package. We would like to thank [PERSON] and [PERSON] for their help in preparing and editing figures.  
The authors declare no conflict of interest.