Yazar "Ilci, Veli" seçeneğine göre listele

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    AN EXPERIMENTAL STUDY ON MAP PROJECTION TRANSFORMATION USING GIS TOOLS
    (Yildiz Technical Univ, 2017) Gokgoz, Turkay; Hacar, Muslum; Memduhoglu, Abdulkadir; Ilci, Veli; Karabulut, Mustafa Fahri; Tekin, Aydemir Can; Ozerdem, Omer Zubeyr
    Topographical maps with the projection of Gauss-Kroger/Transverse Mercator (GK/TM) and Universal Transverse Mercator (UTM) are the primary inputs in many applications related to Geosciences. In these projections, each zone contains a separate coordinate system. For this reason, two adjoining map sheets located in different zones cannot be side by side theoretically. In such situations, map sheets must first be positioned on the same coordinate system in a geographical information system. In this study, three different transformations were performed using AutoCAD Map 3D, QGIS, MicroStation, ArcMap, Netcad, and Global Mapper: (1) among 3 degrees adjoining GK/TM zones, (2) from 3 degrees GK/TM to 6 degrees UTM, and (3) from 3 degrees GK/TM to the tangent and secant Lambert Conformal Conic (LCC) projection. The results were compared in terms of ellipsoidal values, projections, and programs. There were several limitations in the programs with regards to measurement, process precision, and deficiencies in terms of users. Since all three projections were conformal, angles were preserved. However, lengths that were different in each projection were also different from the ellipsoidal values, with the exception of secant LCC projection. Consequently, the appropriate method and program should be selected depending on the geographical location of study area, objective, expected accuracy, and precision.
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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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    DETERMINATION OF RESERVOIR SEDIMENTATION WITH BATHYMETRIC SURVEY: A CASE STUDY OF OBRUK DAM LAKE
    (Parlar Scientific Publications (P S P), 2019) Ilci, Veli; Ozulu, Ibrahim Murat; Alkan, Reha Metin; Erol, Serdar; Uysal, Murat; Kalkan, Yunus; Seker, Dursun Zafer
    The sediments that transported in different ways to dam reservoirs decrease water storage capacity and shortens the reservoir lifetime. This forces the manager of water resources to monitor changes in water floor topography, and determine the sediment amount and sedimentation rate. This is very important in order to maintain current operations, make correct planning for future needs, take necessary precautions to prevent having a shorter lifetime than the projected durations and prolong the dams' lifetime. Although there are several different methods for determining the amount and rate of sediments, the most commonly used one is the bathymetric survey. In this study, in order to determine sedimentation of dams, a bathymetric survey was conducted in a part of the Obruk Dam Lake located in the Corum province of Turkey with the most recent geodetic equipment. The obtained results from the bathymetric survey are considered as initial results for the upcoming measurements to monitor the changes in sediment amount and sedimentation rate in the selected part of the Obruk Dam. The results imply that; the bathymetric surveying method is a powerful tool to estimate reservoir sedimentation.
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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.
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    Performance Comparison of 2.4 and 5 GHz WiFi Signals and Proposing a New Method for Mobile Indoor Positioning
    (Springer, 2020) Ilci, Veli; Gulal, Engin; Alkan, Reha Metin
    Nowadays, the location information of people and objects is a necessity for indoor environments. Therefore, many technologies, methods, and algorithms have been employed in recent years to estimate the positions of people and objects. Although there has been much research into different methods, none of these methods has yet been accepted as a common solution for accurate indoor positioning. Therefore, there is still a lot of work to be done in this area of research. WiFi-based indoor positioning applications are one of the most popular research topics due to not requiring any additional hardware or cost. However, WiFi signals are influenced by many environmental effects, and thus, they show unstable behaviors in indoor environments. Because of the fluctuation of WiFi signal behavior, WiFi-based systems cannot provide sub-meter level accurate solutions. In this paper, we aimed at two main contributions. First, we analyzed and compared the 2.4 and 5 GHz WiFi signal behaviors based on the distance. For this purpose, we conducted an experiment using access points along a 27.83 m corridor with 0.605 m intervals in an indoor environment. This experiment showed that the 5 GHz WiFi signal behaviors are more stable than the 2.4 GHz signals. For this reason, it is expected that 5 GHz WiFi signals enable more accurate distance and position information as compared to the 2.4 GHz signals. Secondly, we performed six real-time kinematic experiments on two different trajectories with two main objectives. The first objective was to compare the positioning performances of 2.4 and 5 GHz WiFi signals. As expected from the first experiment results, positioning accuracies obtained from 5 GHz signals are significantly better than 2.4 GHz signals. In the second objective, we proposed a new algorithm that mainly consists of a fusion of the Bilateration and extended Kalman filter (EKF) algorithms. The main purpose of this algorithm is to diminish the effects of faulty received signal strength values on positioning, and therefore, improve the positioning accuracy of the mobile devices. It concluded that the proposed algorithm dramatically improves the positioning accuracy as compared to the Bilateration and EKF algorithms.
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    THE USAGE OF UNMANNED AERIAL VEHICLES (UAVs) FOR 3D MAPPING OF ARCHAEOLOGICAL SITES
    (Parlar Scientific Publications (P S P), 2019) Ilci, Veli; Ozulu, Ibrahim Murat; Bilgi, Serdar; Alkan, Reha Metin
    In archaeological sites, mapping, documentation, registration, and visualization of cultural heritage is very important for both cultural heritage's conservation, understanding of the historical importance and to transmit future generations. Traditionally, mapping and documentation studies are carried out through terrestrial measurements performed during excavation or at the end of each workday. Together with the improvements in image acquisition and processing techniques, Unmanned Aerial Vehicles (UAVs) have become an alternative for many applications including archaeological areas, historic sites, and cultural heritage buildings with accurately and efficiently. The UAVs provide the user low cost, fast data collection even in real-time, and application flexibility for mapping especially of small areas. This study aimed to investigate the usability of UAVs for 3D mapping of archaeological sites. For this purpose, two measurement campaigns were carried out in two different archaeological sites, AlacahoyUk and Sapinuva. From the outcome of this study, it is clear that aerial maps and 3D models of the studied sites were produced with UAV measurements within a cm to dm level of accuracy in a fast and cost-effective manner. In general, the results show that UAVs can be used for many archaeological mapping and documentation studies as a strong alternative to high cost and labor conventional terrestrial and photogrammetric surveying methods.
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    Two-Dimensional Error Estimation in Point Positioning with Fuzzy Logic
    (Ieee, 2018) Bulbul, Mehmet Akif; Ozturk, Celal; Ilci, Veli; Ozulu, Ibrahim Murat
    Developments in technology and computer aims to facilitate the human life. Every new technology developed by computer science is tried to integrate into systems. Rapidly developing satellite, navigation and geographic information systems also use computer science. The position information that these systems provide to people has had too much importance in recent years. The low margin of error in point position estimation has become a criterion for developed technologies. In this study, a model based on fuzzy logic is developed for estimation of point position error. With this derived model, point position error prediction has been determined and the accuracy of estimates of the system has been measured.