Yazar "Atiz, Omer Faruk" seçeneğine göre listele

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    Comparative analysis of real-time precise point positioning method in terms of positioning and zenith tropospheric delay estimation
    (Taylor & Francis Ltd, 2023) Atiz, Omer Faruk; Alcay, Salih; Ogutcu, Sermet; Bugdayci, Ilkay
    The positioning performance of widely used real-time precise point positioning (RT-PPP) software packages BNC, RTKLIB, and PPP-WIZARD were tested in terms of convergence time and accuracy. The convergence time of PPP-WIZARD solutions is reduced by ambiguity resolution (AR). The GPS + GLONASS + GALILEO (GRE) mode improved the convergence time of GPS + GALILEO (GE) mode by 22.0%, 15.5%, 17.1%, and 11.4% for the BNC, RTKLIB, PPP-WIZARD (AR) and PPP-WIZARD, respectively. For the GRE mode, RMSEs of the BNC, RTKLIB, PPP-WIZARD (AR), and PPP-WIZARD software packages in the horizontal/vertical component are 3.8/5.6, 2.6/6.2, 3.3/6.5, 4.3/7.0 cm, respectively. In comparison with the IGS-ZTD (International GNSS Service ZTD), BNC, RTKLIB, PPP-WIZARD (AR), and PPP-WIZARD solutions show a mean bias of 0.28, -0.72, 2.80, and 2.83 cm, respectively in GE mode. The GRE mode reduced the RMSEs of the ZTD estimations of BNC, RTKLIB, PPP-WIZARD (AR) and PPP-WIZARD by 2.9%, 5.1%, 0.6%, and 0.4% respectively.
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    Comparative analysis of the performance of Multi-GNSS RTK: A case study in Turkey
    (Selcuk Univ Press, 2022) Atiz, Omer Faruk; Konukseven, Ceren; Ogutcu, Sermet; Alcay, Salih
    The Real Time Kinematic (RTK) method is widely used in the land surveying. Whereas RTK method has the advantage of practical use, positioning accuracy depends mostly on the baseline length due to the atmospheric errors. In general, RTK measurements are made by using GPS and GLONASS satellite systems. For this reason, the positioning performance of the technique is adversely affected under restricted satellite geometry conditions such as urban canyons. At present, most receivers on the market have the ability to track signals of Galileo and BeiDou satellites. Therefore, in this study, the positioning performance of RTK with different satellite combinations (GPS-only, GPS+GLONASS, GPS+GLONASS+GALILEO+BeiDou) was examined with a comparative approach. A field test was carried out considering approximately 20, 40, 60, and 80 km length of baselines. Three different cut off elevation angles - namely, 10 degrees, 20 degrees, and 30 degrees - were chosen for the field test. The results were investigated in terms of accuracy and precision. Also, the ground truth coordinates of the rovers were obtained by post-processing relative method using GAMIT/GLOBK software. The results showed that multi-GNSS combinations provided better repeatability at the 10 degrees cut off angle option. The accuracy of GPS-only solutions varied between 0.63/2.17 cm and 2.40/4.94 cm for horizontal and vertical components, respectively. However, the multi-GNSS combinations did not have a remarkable superiority in terms of position accuracy even at high satellite cut off angle (30 degrees) compared to the GPS-only RTK.
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    Investigation of the performance of Real-Time Precise Point Positioning (RT-PPP) method using different software packages
    (Geomatik Journal, 2021) Alcay, Salih; Atiz, Omer Faruk
    The Precise Point Positioning technique (PPP), which emerged as an alternative to the conventional relative positioning method, has been widely used in many applications in recent years. The PPP method is a special case of absolute positioning method, in this method the static and kinematic position can be determined with high accuracy by using single GNSS receiver. On the other hand, thanks to the real-time precise orbit and clock products made available by different establishments and organizations (International GNSS Service-IGS, Federal Agency for Cartography and Geodesy-BKG, European Space Agency-ESA, European Reference Frame-EUREF, German Research Centre for Geosciences-GFZ etc.), PPP method has started to be used in applications that require real-time position information. The high interest in this method, which is called real-time-PPP (RT-PPP), has accelerated the development of the method. Many software have been developed in this context. In this study, the positioning performance of RT-PPP method was investigated using BKG/BNC (BKG Ntrip Client), RTKLIB/RTKNAVI (Real Time Kinematic Library) and PPP-WIZARD (PPP With Integer and Zero-difference Ambiguity Resolution Demonstrator) software. For this purpose, real time coordinate values of ISTA IGS station, located in Istanbul, belongs to the observation period of about 25 hours were obtained in 1 second epoch interval. The obtained results were compared with the reference coordinates of the station, and examined in terms of accuracy and precision. According to the results, it has been observed that the convergence time sometimes exceeds 1 hour, and after this time, an accuracy of approximately +/- 10 cm in horizontal component and +/- 20 cm in vertical component could be obtained with BKG/BNC and RTKLIB/RTKNAVI. However the accuracy of the coordinates obtained using the PPP-WIZARD software is over +/- 30 cm due to the large number of disconnections and subsequent convergence.
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    Performance investigation of LAMBDA and bootstrapping methods for PPP narrow-lane ambiguity resolution
    (Taylor & Francis Ltd, 2021) Atiz, Omer Faruk; Ogutcu, Sermet; Alcay, Salih; Li, Pan; Bugdayci, Ilkay
    Precise point positioning with ambiguity resolution (PPP-AR) is a powerful tool for geodetic and time-constrained applications that require high precision. The performance of PPP-AR highly depends on the reliability of the correct integer carrier-phase ambiguity estimation. In this study, the performance of narrow-lane ambiguity resolution of PPP using the Least-squares AMBiguity Decorrelation (LAMBDA) and bootstrapping methods is extensively investigated using real data from 55 IGS stations over one-month in 2020. Static PPP with 24-, 12-, 8-, 4-, 2-, 1- and 1/2-h sessions using two different cutoff angles (7 degrees and 30 degrees) was conducted with three PPP modes: i.e. ambiguity-float and two kinds of ambiguity-fixed PPP using the LAMBDA and bootstrapping methods for narrow-lane AR, respectively. The results show that the LAMBDA method can produce more reliable results for 2 hour and shorter observation sessions compared with the bootstrapping method using a 7 degrees cutoff angle. For a 30 degrees cutoff angle, the LAMBDA method outperforms the bootstrapping method for observation sessions of 4 h and less. For long observation times, the bootstrapping method produced much more accurate coordinates compared with the LAMBDA method without considering the wrong fixes cases. The results also show that occurrences of fixing the wrong integer ambiguities using the bootstrapping method are higher than that of the LAMBDA method.
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    Performance investigation of Trimble RTX correction service with multi-GNSS constellation
    (Taylor & Francis Ltd, 2023) Atiz, Omer Faruk; Shakor, Abbas Qader; Ogutcu, Sermet; Alcay, Salih
    In the middle of 2011, Trimble introduced the RTX correction service to support RT-PPP applications. In this study, the performance of Trimble RTX correction service is investigated over a one-month period using five different GNSS constellations - namely, GPS-only, GPS + GLONASS, GPS + Galileo, GPS + GLONASS + Galileo, and GPS + GLONASS + Galileo + BeiDou. The results show that positioning accuracy and convergence time are significantly improved with the use of the multi-GNSS constellation compared with the GPS-only solution. The result of the converged positioning accuracy indicates that the GPS + GLONASS + Galileo + BeiDou combination improves the accuracy by 63%, 54%, and 60% for north, east, and up components, respectively, compared with the GPS-only solution. The mean convergence time is reduced by the GPS + GLONASS+ Galileo + BeiDou combination by 70%, 71%, and 38.6% compared with the GPS-only solution in the north, east, and up components, respectively. 1.2 (north), 1.5 (east), and 2.3 cm (up) root mean square errors (RMSEs) of converged positioning from the GPS + GLONASS + Galileo + BeiDou combination are computed.