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    The effect of GLONASS on position accuracy in CORS-TR measurements at different baseline distances
    (Selcuk Univ Press, 2022) Yurdakul, Omer; Kalayci, Ibrahim
    GLONASS system; It has become the second system operating on a global scale after the GPS system in the world, after completing the satellite constellation and using it at full capacity as of 8 December 2011. Due to the increasing need for high accuracy and precision real-time location information, CORS networks have become widespread in the world. In Turkey, it was established as CORS-TR and opened for use in December 2008. Comprehensive studies investigating the effects of Network-Based RTK techniques (VRS, FKP, and MAC) in the COR-STR network are very limited due to the fact that the GLONASS system has been used at full capacity recently. In this paper, it is aimed to determine the effect of measurements derived from the Network-Based RTK techniques in the CORS-TR network of the GLONASS system on the location accuracy, and thus to make a business plan according to the accuracy and precision requirements of all civil and military users. For this purpose, simultaneous measurements were made with 6 GNSS receiver devices of the same brand and model. A total of 308,908 epoch data (northing value, easting value, and ellipsoidal height: projection coordinates (ITRF96 Datum, 2005.00 Reference Epoch)) were collected at one-second intervals in each technique and for seven days of measurements. As a result of the evaluation and analysis of the data sets obtained with the measurements; It has been observed that the GLONASS system has a positive effect on position accuracy, but in some cases, it also has disruptive effects. It has been observed that the most important contribution is to increase the number of visible satellites and to enable measurements with GLONASS satellites in cases where GPS satellites alone are not sufficient, especially in areas where the satellite elevation angle is narrowed, such as city centers, and forest areas.
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    Performance investigation of GLONASS in the static PPP technique with independent short measurement times using online processing services
    (Taylor & Francis Ltd, 2023) Yurdakul, Omer
    The precise point positioning (PPP) technique, which is still being developed, provides position accuracy at the centimetre (cm) level and is widely employed in scientific research. In the PPP technique, cm-level accuracy can be achieved by evaluating raw data obtained from a single Global Navigation Satellite Systems (GNSS) receiver using precise satellite orbit and clock correction data and other parameters. The majority of studies in the literature are based on 24-hour data obtained from the International GNSS Service (IGS) and similar stations. However, there are fewer articles in which analyzes based on short-term measurements are taken. In this study; the effect of GLONASS on the static PPP technique was investigated with independent short measurement times. For this purpose, measurements were made at 7 different test points on consecutive days using a single GNSS receiver. A 4-hour static measurement was made at each test point. The data obtained were processed in two different scenarios, only GPS and GPS + GLONASS using the Canadian Spatial Reference System - PPP (CSRS-PPP) and Trimble RTX online process software. The processes were completed at 4, 2, 1, and 0.5 h. As a result of the analysis, it has been observed that GLONASS improves the results by 76%, but negatively affects some solutions (24%). It was also observed that GLONASS drastically reduced the outlier values. With this study, it is aimed to show the accuracy that users who make short-term measurements with a single GNSS receiver can be achieved in the static PPP technique by using GPS + GLONASS systems, with repeated measurements.