Investigation on the usability of online GNSS data processing services; Iraq, Duhok region example

In this thesis study, GNSS measurements ranging from 6 to 8 hours in 10 points established in Duhok region of Iraq were done to investigate the usability of online GNSS services and the measurements were evaluated both by LOGO, a commercial software, and by OPUS, AUSPOS, TRIMBLE RTX and CSRS-PPP services, which evaluate online GNSS data. In the first part, importance, advantages, and disadvantages of GNSS measurements and softwares and the studies on this subject have been discussed. In the second chapter, GNSS is given briefly, GNSS measurement and GNSS error sources are mentioned. The third section provides information on commercial and academic software, on-line GNSS evaluation services, how these services work, sending data and getting results reports. In the fourth chapter, it is discussed whether the GNSS coordinates evaluated by both LGO (a commercial software) and OPUS, AUSPOS, TRIMBLE RTX, and CSRS-PPP (online GNSS services) of 10 points are compatible. It has been seen that the standard deviations of the cartesian coordinates (ITRF08) and coordinates obtained for the 10 points are roughly compatible. For accuracy analysis of coordinates from online services, the coordinates with the best coordinate accuracy obtained with the LGO software which was evaluated step by step with reference to the nearest IGNSS network points in the region were taken as references. LGO-CSRS PPP and LGO-TRIMBLE RTX coordinate differences (X, Y and Z) were found to be slightly better than the other services (LGO-OPUS and LGO AUSPOS) when the differences between the reference coordinates and the coordinates obtained from online services were examined. To statistically determine whether the coordinates are compatible, the coordinate differences were tested with t-distribution at α=0.05 error probability. The test result is that the coordinate differences are significant, and it was seen that the coordinates obtained from online services are not compitable with the coordinates obtained with the LGO software. In addition, the CSRS-PPP service coordinates (the accuracy of coordinates is better than the accuracy of coordinates obtained from other services) are referenced to determine the consistency of the coordinates obtained from CSRS-PPP, AUSPOS, TRIMBLE-RTX and OPUS services. The reference coordinates were differentiated from the coordinates of the other services and the differences were tested in the same way at α=0.05 error probability. In the coordinate differences, the CSRS PPP results are in agreement with the TRIMBLE RTX results (differences between 1 cm and 1 mm), the CSRS PPP-OPUS and CSRS PPP-AUSPOS differences are also close to each other. It has also been found statistically that the CSRS PPP-TRIMBLE RTX coordinate differences (for X, Y, and Z) are insignificant at α=0.05 error probability.