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Öğe Aktif Küresel Navigasyon Uydu Sistemleri ile RTK performansının incelenmesi(2021) Konukseven, Ceren; Alçay, SalihKüresel Navigasyon Uydu Sistemi (GNSS), kullanıcılara hızlı, uygun maliyetli ve güvenilir bir konum belirleme hizmeti sağlamaktadır. Gerçek zamanlı kinematik (RTK) yöntemi birçok mühendislik uygulamasında gerçek zamanlı konumlama için pratik bir araç haline gelmiştir. RTK yönteminin doğruluğu, yörünge hatası ve atmosferik hatalar nedeniyle referans istasyonu ile gezici arasındaki baz mesafesine bağlıdır. Ayrıca günümüzde RTK düzeltmeleri internet protokollerinin gelişimiyle birlikte GSM üzerinden iletilebilmekte olup radyo modemden kaynaklanan mesafe sınırlandırılması da ortadan kalkmıştır. RTK ölçmeleri genel olarak GPS ve GLONASS uydu sistemleri kullanılarak gerçekleştirilmektedir. Ancak günümüzde GALILEO ve BEIDOU gibi yeni GNSS sistemleri de kullanıcıların hizmetine sunulmuştur. Bu tez çalışmasında internet tabanlı klasik RTK yöntemi kullanılarak çoklu GNSS kombinasyonlarının performansını test etmek amacıyla farklı baz mesafeleri (~20, ~40, ~60, ~80 km) dikkate alınarak, Konya’da arazi çalışmaları yapılmıştır. Ölçüm yapılan noktalarda eşit koşullara sahip 3 gezici alıcı kullanılarak sadece GPS, GPS+GLONASS, GPS+GLONASS+GALILEO+BEIDOU uydu konfigürasyonlarında ölçümler yapılmıştır. RTK koordinatları farklı uydu konfigürasyonları ile her uygulama noktasında yaklaşık 9 saat olmak üzere 10°, 20° ve 30° yükseklik açılarında üç oturum şeklinde elde edilmiştir. Her uygulama noktasında ilk oturumlarda (10°) yaklaşık 5 saatlik RTK ölçümlerinin yanı sıra statik veri kaydı da alınmıştır. Gezici alıcıların gerçek koordinatları, statik verilerin GAMIT/GLOBK akademik yazılımı kullanılarak, bağıl yöntemle değerlendirilmesiyle elde edilmiştir. Elde edilen sonuçlar tekrarlılık ve doğruluk açısından değerlendirilmiştir. Çoklu GNSS kombinasyonlarının 10° uydu yükseklik açısında RTK performansını tekrarlılık açısından iyileştirdiği görülmüştür. Yalnız GPS çözümlerinin doğruluğu yatay ve düşey bileşenler için sırasıyla 0.63/2.17cm ve 2.40/4.94cm arasında değişmiştir. Ancak RTK yöntemi için çoklu GNSS kombinasyonlarının, yalnız GPS’e göre uydu yükseklik açısı 30° seçildiğinde bile doğruluk açısından dikkate değer bir üstünlüğe sahip olmadığı sonucuna ulaşılmıştır.Öğe Assessing the performance of BDS-3 for multi-GNSS static and kinematic PPP-AR(Elsevier, 2023) Öğütçü, Salih Sermet; Alçay, Salih; Özdemir, Behlül Numan; Li, Pan; Zhang, Yize; Konukseven, Ceren; Atiz, Ömer FarukAs of 2021, a total of four different GNSS constellations - namely, GPS, GLONASS, Galileo, and BDS-3 - can be used with Full Operational Capability (FOC). In this work, the contribution of BDS-3 FOC to GPS + GLONASS + Galileo (GRE) PPP-AR is inves-tigated, considering the three different cut-off angles (7 degrees, 30 degrees, and 45 degrees) and different lengths of static observation sessions (24-, 12-, 6-, 3-, 1-, 0.5-, 0.25-hour). The data of 31 IGS-MGEX stations is processed with GRE PPP-AR and GREC3 (GPS + GLONASS (using float mode) + Galileo + BDS-3) PPP-AR modes. The results showed that BDS-3 degraded the horizontal (except for 24-h sessions) and ver-tical accuracy of static GRE PPP-AR solutions regardless of the elevation cutoff angle and observation time. The kinematic results showed that BDS-3 significantly contributed to the accuracy of GRE kinematic PPP-AR for 30 degrees and 45 degrees cutoff angles. The convergence time analysis showed that BDS-3 only contributes to GRE kinematic PPP-AR for the vertical component.(c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.Öğe 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, SalihThe 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.Öğe GPS plus Galileo + BDS-3 medium to long-range single-baseline RTK: an alternative for network-based RTK?(Cambridge Univ Press, 2023) Ogutcu, Sermet; Alcay, Salih; Ozdemir, Behlul Numan; Duman, Huseyin; Koray, Ulkunur; Konukseven, Ceren; Bilal, Nesibe GulThanks to the development of the real-time kinematic (RTK) algorithm and the emerging Global Navigation Satellite System (GNSS), especially for Galileo and BeiDou-3, reliable positioning accuracy for medium and long-baseline RTK became possible globally. Moreover, with the development of the GNSS receiver hardware, baseline length limitations due to radio-based communications are removed thanks to internet-based communication. In this work, single-baseline RTK, incorporated partial ambiguity resolution with troposphere and ionosphere weighting, using GPS (G), Galileo (E), BeiDou-3 (C3) and multi-GNSS (GE and GEC3), is conducted with real GNSS data of EUREF Permanent GNSS network under three different cutoff angles (10 degrees, 20 degrees, and 30 degrees) for six different lengths of baselines (similar to 50, similar to 150, similar to 250, similar to 350, similar to 450, and similar to 550 km). The results show that the multi-GNSS RTK solution significantly contributed to the positioning accuracy and convergence time of the single-system RTK solutions. Based on the results, non-available epoch-wise solutions for the high-degree cutoff angles are more obvious for the single-system RTK, whereas multi-GNSS solutions provide 100% solutions for each cutoff angle and baseline. The results indicate that instantaneous and a few epochs single-epoch ambiguity resolution is feasible for 50, 150, 250 and 350 km baseline lengths for multi-GNSS RTK. Based on the positioning results, horizontal-vertical positioning improvements of multi-GNSS RTK (GEC3) compared with the single-system GPS RTK are found as 50%-37%, 40%-35%, 55%-47%, 53%-54%, 57%-49% and 57%-49% for 50, 150, 250, 350, 450 and 550 km, respectively, under a 10 degrees cutoff angle. For 20 degrees and 30 degrees cutoff angles, the accuracy improvements are much higher. The convergence time improvements (n/e/u) of multi-GNSS RTK (GEC3) compared with the single-system GPS RTK are found as 86/92/75%, 77/67/72%, 75/77/83%, 53/56/52%, 69/49/62%, and 52/45/39% for 50, 150, 250, 350, 450 and 550 km, respectively, under a 10 degrees cutoff angleÖğe Static and kinematic PPP-AR performance of low-cost GNSS receiver in monitoring displacements(Elsevier Sci Ltd, 2023) Ogutcu, Sermet; Alcay, Salih; Duman, Huseyin; Ozdemir, Behlul Numan; Konukseven, CerenRecently, low-cost GNSS receivers have played a significant role in displacement monitoring studies due to the increasing availability of mass-market applications. In this work, the performance of static and kinematic PPP-AR using a low-cost u-blox ZED-F9P GNSS receiver in monitoring displacements is investigated by comparing it with a geodetic-grade GNSS receiver using a displacement simula-tion apparatus. The capability to determine the horizontal displacement direction is also investigated for both receivers. The results showed that one-sigma horizontal / vertical RMSEs computed from the true displacements and computed displacements are 1.4 / 5.6 mm and 2.6 / 8.4 mm for the geodetic and u-blox receivers, respectively, using 24-h data with static GPS + GLONASS PPP-AR. It is found that GLONASS contribution to GPS-only static PPP is more evident for the u-blox receiver compared with the geodetic one. RMSEs are found to be higher as observation times are decreased. The post-processed kinematic test results showed that minimum 10 / 20 and 20 / 30 mm horizontal / vertical dynamic displacements can be visually detected as an offset from the daily time series for the geodetic and u-blox receivers, respectively.(c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.
