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Yayın A point cloud filtering method based on anisotropic error model(John Wiley and Sons Inc, 2023-12) Özendi, Mustafa; Akça, Devrim; Topan, HüseyinMany modelling applications require 3D meshes that should be generated from filtered/cleaned point clouds. This paper proposes a methodology for filtering of terrestrial laser scanner (TLS)-derived point clouds, consisting of two main parts: an anisotropic point error model and the subsequent decimation steps for elimination of low-quality points. The point error model can compute the positional quality of any point in the form of error ellipsoids. It is formulated as a function of the angular/mechanical stability, sensor-to-object distance, laser beam's incidence angle and surface reflectivity, which are the most dominant error sources. In a block of several co-registered point clouds, some parts of the target object are sampled by multiple scans with different positional quality patterns. This situation results in redundant data. The proposed decimation steps removes this redundancy by selecting only the points with the highest positional quality. Finally, the Good, Bad, and the Better algorithm, based on the ray-tracing concept, was developed to remove the remaining redundancy due to the Moiré effects. The resulting point cloud consists of only the points with the highest positional quality while reducing the number of points by factor 10. This novel approach resulted in final surface meshes that are accurate, contain predefined level of random errors and require almost no manual intervention.Yayın Determining pull-out deformations by means of an online photogrammetry monitoring system(Cem Gazioğlu, 2015-03-02) Avşar, Emin Özgür; Altan, Mehmet Orhan; Doğan, Ünal Anıl; Akça, DevrimChemical anchorages are applied in many engineering implementations, particularly strengthening of reinforced concrete structures. During strengthening procedure; chemical anchorages should be tested, since they supply to transfer the load between existing construction elements and newly added elements. Therefore; the study of the quality of chemical anchorages is an important issue in construction materials science. In this context; the most important experiment is to determine the pull-out loads of embedded anchorage reinforcement by applying axial loads. In this study; it is aimed to determine the displacements of steel reinforcements, embedded into concrete by using chemical anchorages, while applying axial pulling loads. In order to determine the displacements and load - deformation graphs; starting conditions and every 10 bar pressure applied conditions of the steel reinforcements were captured by the cameras. The obtained images were evaluated by using photogrammetric software. Based on the photogrammetric post-processing results, the load - deformation graphs were plotted and the loads at loss of adhesion were determined.Yayın Mixed-reality photogrammetry in focus(Reed Business-Geo, 2024) Kemper, Gerhard; Torkut, Çağın; Akça, Devrim; Grün, ArminThe use of mixed reality in photogrammetry software has resulted in a real -time 3D inspection system that allows users to remotely access, visualize and measure the stereoscopic model simultaneously. An on-site operator runs a drone equipped with a stereo camera, and thanks to virtual reality headsets experts can observe the object of interest without leaving the office. This improves both cost-effectiveness and safety when inspecting large, critical structures.Yayın Photogrammetry-The science of precise measurements from images: a themed issue in Honour of Professor Emeritus Armin Grün in anticipation of his 80th birthday(Multidisciplinary Digital Publishing Institute (MDPI), 2024-12) Qin, Rongjun; Akça, Devrim; Remondino, Fabio[No abstract available]Yayın Real-time 3D inspection of large civil structures using a stereoscopic camera system equipped UAV(International Society for Photogrammetry and Remote Sensing, 2024-12-13) Akça, Devrim; Torkut, Çağın; Kemper, Gerhard; Kunz, Noah; Caner, Doğa; Gruen, ArminREALTIME3D is an innovative Mixed-Reality (MR) photogrammetry system that integrates photogrammetry, UAV technology, and VR/AR solutions to enable real-time 3D infrastructure inspection. By combining these technologies, the system allows users to remotely access, visualize, and measure 3D stereoscopic models in real time. An operator on-site pilots a UAV equipped with the stereo cameras, while experts, utilizing VR headsets, can observe and analyze the object of interest from remote locations. This approach enhances cost efficiency and safety during inspections of large-scale, critical structures. The paper introduces the first prototype of the system, detailing its hardware and software components.
