Yazar "Ozulu, I. Murat" seçeneğine göre listele

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    Comparative analysis of real-time kinematic and PPP techniques in dynamic environment
    (Elsevier Sci Ltd, 2020) Alkan, Reha Metin; Erol, Serdar; Ilci, Veli; Ozulu, I. Murat
    The main objective of this study is to assess the performance of the relative Real-time Kinematic (RTK) Global Navigation Satellite System (GNSS) Methods; i.e., Single-baseline & Network RTK, and Real-time Precise Point Positioning (RT-PPP); i.e., Trimble CenterPoint Real Time eXtended (RTX) Correction Service in a dynamic environment. For this purpose, a kinematic test was done within a vessel in Obruk Lake Dam in Corum province, Turkey. The test area was situated in a deep valley and surrounded by high hills covered with dense trees. The real-time coordinates of each measurement epoch were simultaneously determined with Single-baseline RTK, Network RTK, and RTX RT-PPP methods by using three GNSS receivers. The real-time coordinates obtained from both RTK and RT-PPP methods were compared against the post-processed relative solution epoch-by-epoch. The results show that, the 3D position accuracies of real-time methods were found as +/- 6 cm, +/- 3 cm and +/- 7 cm for Single-baseline RTK, Network RTK and RT-PPP methods, respectively. This study demonstrates that although the Network RTK methods provided the best solution among the others, the positioning did not conduct most of the time due to the loss of cellular connection. This was also partially valid for the Single-baseline RTK method because the corrections from the base station via radio-link couldn't be received due to the rough terrain conditions. However, it was possible to make positioning with RTX Real-time PPP technique using satellite delivery GNSS products (corrections) continuously and in a robust manner within the cm-level accuracy. Our study showed that the use of the global multi-GNSS RTX correction service outcompetes conventional RTK methods with providing consistent, reliable, and seamless cm-level accurate positioning almost without any interruption especially in challenging marine environments with severe terrain obstructions. (C) 2020 Elsevier Ltd. All rights reserved.
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    Impact of different sampling rates on precise point positioning performance using online processing service
    (Taylor & Francis Ltd, 2021) Erol, Serdar; Alkan, Reha Metin; Ozulu, I. Murat; Ilci, Veli
    In this study, the effect of different sampling rates (i.e. observation recording interval) on the Precise Point Positioning (PPP) solutions in terms of accuracy was investigated. For this purpose, a field test was carried out in corum province, Turkey, on 11 September 2019. Within this context, a Geodetic Point (GP) was established and precisely coordinated. A static GNSS measurement was occupied on the GP for about 4-hour time at 0.10 second (s)/10 Hz measurement intervals with the Trimble R10 geodetic grade GNSS receiver. The original observation file was converted to RINEX format and then decimated into the different data sampling rates as 0.2 s, 0.5 s, 1 s, 5 s, 10 s, 30 s, 60 s, and 120 s. All these RINEX observation files were submitted to the Canadian Spatial Reference System-Precise Point Positioning (CSRS-PPP) online processing service the day after the data collection date by choosing both static and kinematic processing options. In this way, PPP-derived static coordinates, and the kinematic coordinates of each measurement epoch were calculated. The PPP-derived coordinates obtained from each decimated sampling intervals were compared to known coordinates of the GP for northing, easting, 2D position, and height components. According to the static and kinematic processing results, high data sampling rates did not change the PPP solutions in terms of accuracy when compared to the results obtained using lower sampling rates. The results of this study imply that it was not necessary to collect GNSS data with high-rate intervals for many surveying projects requiring cm-level accuracy.
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    Performance analysis of real-time and post-mission kinematic precise point positioning in marine environments
    (Science Press, 2020) Erol, Serdar; Alkan, Reha Metin; Ozulu, I. Murat; Ilci, Veli
    This article focuses on the performance analysis of both real-time and post-mission kinematic precise point positioning (PPP) in challenging marine environments. For this purpose, a real dynamic experiment lasting 6 h was carried out on a lake dam in Corum City of Turkey. While the kinematic test was continuing, the real-time PPP coordinates were obtained for each measurement epoch with a commercial real-time PPP (RT-PPP) service, namely the Trimble CenterPoint RTX. Then the post-mission PPP (PM-PPP) coordinates were calculated by using Multi-GNSS data and the Multi-GNSS Experiment (MGEX) precise products. The kinematic RT-PPP and PM-PPP results showed that the PPP coordinates were consistent with the relative solution at centimetre and decimetre level in horizontal and height components, respectively. This study implies that PPP technique is a powerful tool for highly accurate positioning in both real-time and post-mission modes, even for dynamic applications in harsh environments. (C) 2020 Institute of Seismology, China Earthquake Administration, etc. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.