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www.sea-technology.com May 2016 / st 39 The collected GNSS data on the vessel were sent to CSRS-PPP, GAPS and magicGNSS online services via email or using their websites by choosing the kinematic process- ing option. The kinematic PPP coordinates for each mea- surement epoch and some fles with additional informa- tion were retrieved a short time later. The kinematic PPP coordinates were then compared with the vessel reference trajectory, epoch-by-epoch, to analyze PPP accuracy per- formance. The results were also investigated statistically, with minimum, maximum, mean differences and root mean square error (RMSE) calculated to see the differences. The results indicate that the CSRS-PPP service is the best solution in terms of accuracy. The magicGNSS gives similar results to the CSRS-PPP service, with slightly less accuracy for the height component. GAPS proved not to perform as well as CSRS-PPP and magicGNSS. Conclusion In this study, an accuracy comparison of the kinematic PPP coordinates obtained from three commonly used online PPP processing services—CSRS-PPP, GAPS and magicGNSS—was carried out in dynamic marine envi- ronment using a kinematic test. The results show that the NRCan's CSRS-PPP service offers the best PPP solution for both the 2D position and height components, with accu- racy of a few centimeters to decimeters. magicGNSS pro- duced almost the same results as those obtained through CSRS-PPP for the horizontal component. However, slight- ly less accuracy was obtained for the height component, which reached a maximum value of 19 cm. Of the three services, the worst results were obtained from GAPS, which achieved only a couple of decimeters accuracy on both the horizontal and height components. In gen- eral, it can be concluded that kinematic PPP coordinates converge to the relative online service counterpart with a difference of centimeters to decimeters, resulting in ac- curacy suffcient for many marine applications, including hydrographic surveys, marine geodesy, navigation and oceanography. References For a list of references, contact Reha Metin Alkan at alkanr@itu.edu.tr. ST Dr. Reha Metin Alkan is a professor in the Geomatics Engineering Department at Istanbul Technical Uni- versity (ITU) in Istanbul, Turkey, and is also president of Hitit University in Çorum, Turkey. He holds an M.S. and Ph.D. in geodesy and photogrammetry from the Engineering Department of ITU. His research mainly covers satellite positioning and navigation and engi- neering surveying. Î . Murat Ozulu has a B.S. from Yildiz Technical Uni- versity (YTU) and an M.S. from Anadolu University in Turkey. He is now a Ph.D. candidate at YTU and a lec- turer at Hitit University. His areas of research include geodesy, GNSS, engineering surveying and geodetic documentation studies at archeological sites. Veli Î lçi has a B.S. from Istanbul Technical University and an M.S. from Afyon Kocatepe University, Turkey. He is a Ph.D. candidate at YTU and a lecturer at Hitit University. His areas of research include geodesy, GNSS, indoor positioning, engineering surveying and GIS. Visit us - Booth #1442 www.sbg-systems.com