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    Analysis of Displacement Response of the Ermenek Dam Monitored by an Integrated Geodetic and Pendulum System
    (Springer International Publishing Ag, 2018) Alcay, Salih; Yigit, Cemal Ozer; Inal, Cevat; Ceylan, Ayhan
    This paper studies the structural behavior of the Ermenek arch dam, the second highest dam in Turkey. The investigated period covers the stage of the last-quarter part of first filling (1 and 1/2 year) and the begging of its operational lifetime (1year). Displacement responses of the dam to temperature load and water load are assessed in detail based on both geodetic and pendulum monitoring records. In addition, the present study explores the possibility and advantage of integrating pendulum-measured signals with geodetic-measured signals for the dam deformation monitoring. The analysis results reveal that pendulum-derived displacements at four gallery levels, along the vertical cross section of the dam, which exhibit periodicity and linear trend with different slope due to seasonal temperature oscillation and linearly increased reservoir level, respectively. Comparative evaluation of the results shows that there is very good agreement between geodetic-derived displacement in radial direction at the middle of the crest and corresponding pendulum-derived displacement.
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    Displacement monitoring performance of relative positioning and Precise Point Positioning (PPP) methods using simulation apparatus
    (Elsevier Sci Ltd, 2019) Alcay, Salih; Ogutcu, Sermet; Kalayci, Ibrahim; Yigit, Cemal Ozer
    Besides the classical geodetic methods, GPS (Global Positioning System) based positioning methods are widely used for monitoring crustal, structural, ground etc., deformations in recent years. Currently, two main GPS positioning methods are used: Relative and Precise Point Positioning (PPP) methods. It is crucial to know which amount of displacement can be detected with these two methods in order to inform their usability according to the types of deformation. Therefore, this study conducted to investigate horizontal and vertical displacement monitoring performance and capability of determining the direction of displacements of both methods using a developed displacement simulator apparatus. For this purpose, 20 simulated displacement tests were handled. Besides the 24 h data sets, 12 h, 8 h, 4 h and 2 h subsets were considered to examine the influence of short time spans. Each data sets were processed using GAMIT/GLOBK and GIPSY/OASIS scientific software for relative and PPP applications respectively and derived displacements were compared to the simulated (true) displacements. Then statistical significance test was applied. Results of the experiment show that using 24 h data sets, relative method can determine up to 6.0 mm horizontal displacement and 12.3 mm vertical displacement, while PPP method can detect 8.1 mm and 19.2 mm displacements in horizontal and vertical directions respectively. Minimum detected displacements are found to grow larger as time spans are shortened. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.
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    Network based performance of GPS-only and combined GPS/GLONASS positioning under different sky view conditions
    (Springer, 2017) Alcay, Salih; Yigit, Cemal Ozer
    This paper offers a comprehensive assessment of network-based positioning results using GPS-only and combined GPS/GLONASS data under open to limited sky view conditions. Data analysis is performed in a short (4 h) and a long (24 h) term spanning observations from five GNSS stations using 10 degrees, 20 degrees, 30 degrees and 40 degrees elevation cut-off angles, which simulate the availability of satellites in different sky view conditions. Evaluation of the results reveals insignificant differences between the accuracy of the GPS-only and combined GPS/GLONASS solutions for daily observation in all sky view conditions. However the clear advantage of integrating GPS and GLONASS observation in a GNSS differential solution is apparent for short (4 h) observation periods, particularly at the highest elevation cut-off angle (40 degrees).