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With the development of technology, objects in the real world are transferred to the virtual environment, making it easier to manage all data flows and processes of the target object. The most important feature of digital twins is that they reflect the real world as accurately and up-to-date as possible. The use of LiDAR and photogrammetry has become very popular in the creation of three-dimensional point clouds of physical environments. Besides being able to represent the real world in detail, one of the most useful features of digital twins is that point clouds are suitable for direct use. In this way, point clouds can be used directly as a three-dimensional geometric model for a digital twin without the need for many processing steps. To update the three-dimensional geometric model, it is necessary to rescan the changed areas, and then perform change detection operations that provide a point cloud of these objects within the change. In this study, the importance and direct use of point clouds in the production of digital twins were examined, and for this purpose, photogrammetric studies were carried out on three sculptures with irregular geometrical structures and complex structures. As a result of the data obtained in the study, it was observed that the models were missing, especially in the parts where depth perception is difficult, and suggestions were made. As a result, it has been found that point clouds produced by SfM-based photogrammetric software provide a great advantage in fast and low-cost data collection to create and update the digital twin. [ABSTRACT FROM AUTHOR]

In recent years, studies on autonomous vehicles have been progressively increasing and especially, intensive works have been carried out in many areas like obstacle detection, mapping, localization, path planning, navigation, and obstacle avoidance. In this study, it was aimed to develop a new 3D LIDAR system with much lower cost, portable and 360-degree field of view by using standard 2D laser scanner instead of high-costing and large dimension 3D LIDARs which contribute seriously to the autonomy of the vehicle. The acquisition of a new 3D LIDAR system is mainly based on the rotation of the 2D laser scanner about certain axis and the conversion of the distance data published by this laser scanner into point cloud data, which is called as the 3D Cartesian point cluster. When the 3D LIDAR system is examined as a whole, it needs to communicate in coordinately the components it contains in order to operate at the desired efficiency. Therefore, in order to manage this software and hardware communication, ROS (Robot Operating System), which is a software platform that can be controlled by the computer, was used. In addition, a mobile vehicle was designed to be gained motion feature to the system. The 3D LIDAR platform was integrated into the designed mobile vehicle and the new system was made ready for navigation. For navigation, a number of algorithm and ROS nodes, called Navigation Stack, were used to autonomously move the vehicle from one point to another and avoid all obstacles that may occur during movement. Experiments show that the developed 3D LIDAR system provides an economical and effective solution for all directional object detection in autonomous vehicles. The navigation tests also show that the developed system is successful in performing tasks such as obstacle detection and obstacle avoidance in indoor environments. [ABSTRACT FROM AUTHOR]

Rockfalls are one of the geological-based natural disasters and it develops in the control of factors such as lithology, discontinuities, slope, decomposition, roughness and vegetation. There are generally 2 and 3 dimensional solutions for the modeling of rock falls in engineering projects. However, 3D solutions have been used frequently in recent years because they simulate the natural environment more precisely. With the widespread use of unmanned aerial vehicles, very valuable data can be collected about the location and block size of discontinuities on steep slopes, which are very difficult to access as well as topography and vegetation creating a point cloud with orthophotos. In this study, potential rock drops in Kasımlar Village of Sütçüler District in Isparta Province were modeled as 3D in Geographic Information Systems with photogrammetric methods using Unmanned Aerial Vehicle. At the same time, the trajectories of falling blocks belongs to possible rockfalls, trajectory, passing heights and energies are calculated and areas under risk are mapped. According to the results of 3D modeling for four blocks ranging in size from 26 m3 to 355 m3, the maximum kinetic energy is 55170kJ, the maximum passing heightis 11.5 m and the maximum simulated velocity are 24.7m/s.. [ABSTRACT FROM AUTHOR]

Four different variants of building detection are presented. Each variant has a different workflow and is capable of detecting buildings. The first variant of building detection is based on multispectral classification and DSM filtering. In the second variant, DSM blobs, mainly consisting of buildings and trees, are detected by subtraction of the DTM from the DSM. Then, trees are eliminated using NDVI data, derived from unsupervised ISODATA classification of the multispectral images, while small non-building objects are rejected based on size criteria. The third variant uses the planimetric density of raw LIDAR DTM data to detect the above-ground objects. The fourth variant is like the third one, but uses the vertical density of the raw LIDAR data (all points) to distinguish trees and buildings. To improve the results, a combination of the four variants using set intersections and unions is performed. The combination was empirical, with consideration of the datasets used in each variant and the advantages and disadvantages of each variant. In the evaluation, the combination of the four individual results yields 94% correct detections and an omission error of 12% for Zurich airport dataset. [ABSTRACT FROM AUTHOR]