## 5 Conclusions  
In this case study, the contribution of the additional satellite systems on kinematic PPP solution performance in terms of accuracy was investigated. In addition, the effects of different MGEX precise satellite orbit and clock products from different IGS Analyzing Centers on the PPP results were also examined. In order to assess these issues, a real kinematic test was carried out and data were collected for 6-h with 1 Hz from a GNSS receiver setup on a vessel. According to Figures 3 and 5, it can be concluded that the additional GNSS constellations improved the observed number of satellites in comparison with that of any single-system constellation. The study reveals that in general, additional GNSS constellations improve the solution accuracy by observing more satellites compared to GPS alone. This is more important when the surveying was carried out in the field where satellite signals are partially obstructed or have multipath potential or have signal loss as a result of obstruction etc. One of the main conclusions of the kinematic test showed that the obtained accuracy was affected by not only the observed GNSS constellations but also highly dependent on the chosen precise orbit and satellite clock products that were introduced in the processing stage. As is known, there are different products provided by a variety of analysis centers, and these centers generally have different datasets, processing strategies, and software for producing their products, and thus, the accuracy and quality of the orbit and clock corrections may differ from each other. According to all solutions conducted here, the GPS+GLONASS+Galileo+BeiDou combination with GFZ's precise products presented the best multi-GNSS PPP performance rather than the other combinations and quad-constellation alternatives using different precise products. The overall results obtained from nine different solutions show that the multi-constellation GNSS kinematic PPP can provide cm- to dm-level of 3D positioning accuracy especially in applications carried out challenging inland waters and marine conditions. Offshore positioning, precise marine engineering, construction, dredging, cable and pipeline laying, ocean buoy positioning, tsunami warning, precise hydrographic surveying, and coastal mapping are examples of these kinds of applications. In addition, the accuracies obtained from this study meet the minimum positional accuracy requirement for preparing nautical charts according to many international hydrographic organizations and authorities regulations, like the International Hydrographic Organization (IHO). This level of accuracy also meets the requirements of most geodetic surveying applications; like dynamic vehicle positioning, autonomous vehicle systems positioning, UAV remote sensing, UAV photogrammetry, mobile mapping systems, aviation, precise agriculture, tectonic geodesy, deformation monitoring, atmospheric water vapor sensing, and low orbiter satellite positioning. This study shows that PPP is a strong alternative to the conventional carrier phase based differential technique in terms of accuracy, ease of use, and operating cost. The study reveals that the performance of multi-constellation GNSS PPP would be improved in the near future after adding more satellites to the existing systems in orbit as well as launching of new satellite systems (such as Korean Positioning System--KPS) and setting up more multi-GNSS reference stations. The initial results of this study were presented as abstract at the GeoPreVi 2018 International Symposium in Bucharest, Romania, between 29-30 October. The author appreciates thanking the Oguzlar Municipality, who provided vessel support to carry out the fieldwork. The author would like to thank [PERSON], [PERSON] and [PERSON] from Hitti University for their support in data collection. The author is grateful to Hitti University for providing software support for this research.