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Simulation of fragmental rockfalls detected using terrestrial laser scans from rock slopes in south-central British Columbia, Canada
摘要： Rockfall presents an ongoing challenge to the safe operation of transportation infrastructure, creating hazardous conditions which can result in damage to roads and railways, as well as loss of life. Rockfall risk assessment frameworks often involve the determination of rockfall runout in an attempt to understand the likelihood that rockfall debris will reach an element at risk. Rockfall modelling programs which simulate the trajectory of rockfall material are one method commonly used to assess potential runout. This study aims to demonstrate the effectiveness of a rockfall simulation prototype which uses the Unity 3D game engine. The technique is capable of simulating rockfall events comprised of many mobile fragments, a limitation of many industry standard rockfall modelling programs. Five fragmental rockfalls were simulated using the technique, with slope and rockfall geometries constructed from high-resolution terrestrial laser scans. Simulated change detection was produced for each of the events and compared to the actual change detection results for each rockfall as a basis for testing model performance. In each case the simulated change detection results aligned well with the actual observed change in terms of location and magnitude. An example of how the technique could be used to support the design of rockfall catchment ditches is shown. Suggestions are made for future development of the simulation technique with a focus on better informing simulated rockfall fragment size and the timing of fragmentation.
关键词： rockfall,simulation,Unity 3D,fragmentation,terrestrial laser scanning
更新于2025-09-12 10:27:22
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Virtual factory layouts from 3D laser scanning – A novel framework to define solid model requirements
摘要： In a world with increasing customer demands, manufacturing companies must develop and produce products more rapidly and adapt their production systems offline, to not disturb the ongoing processes. This creates a demand of using digital production development so that development can be performed in parallel with production. Virtual factory layouts (VFLs) are essential for companies in order to plan their factory layout and evaluate production scenarios. However, requirements for a VFL depends heavily on its purpose. For example, the requirements on a model for offline programming of robots are different from those on a model used to determine buffer locations. There is currently a lack of clear guidelines for how developed a VFL should be to fulfil said requirements, which contributes to unnecessary modelling time and variation in delivery quality. This paper aims to put the actual demands and requirements of a VFL in focus. By adapting a Level of Development-framework for establishment of Building Information Models (BIMs) and connecting it to the purpose of VFLs, development of a framework for detail and functionality level of VFLs is enabled. Such a purpose-oriented framework will help to define delivery packages suited for different circumstances, which will provide the modeler with knowledge of how much detail and functionality a specific model should contain. The increased clarity provided by the developed framework results in a clearer connection between expected result and actual output from a custom VFL project. Also, by connecting model properties or development to the model-purpose, the framework brings clarity and structure to a currently vague field. This provides means for a more efficient and accurate use of VFLs, which will support the rapid development of production facilities.
关键词： layout,virtual factory,3D laser scanning,3D-imaging
更新于2025-09-12 10:27:22
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Object-Based Crack Detection and Attribute Extraction From Laser-Scanning 3D Profile Data
摘要： Cracks in 3D pavement data often show poor continuity, low contrast and different depths, which bring great challenges to related application. Recently, crack attributes, e.g. depth and width have attracted attention of highway agencies for maintenance decision-makings, but few studies have been conducted on crack attributes. This paper presents object-based image analysis (OBIA) method for crack detection and attribute extraction from laser-scanning 3D pro?le data with elevation accuracy about 0.25 mm. Firstly, a high-pass ?lter designed for pavement components in our previous research was applied to remove the ?uctuation posture in 3D data, and then the smallest of-constant false-alarm rate algorithm was used to acquire lower point sets, including crack seeds and lower textures. Secondly, the objects were represented by above obtained 3D point sets and OBIA, especially, the depth statistics, shape and topological features of objects were described. Moreover, to enhance crack objects and remove texture objects gradually, multi-scale object selections and merges were conducted according to the local statistical characteristics differences of objects. Thirdly, the objects’ orientation attributes were combined with tensor voting to connect and infer ?nal crack objects, and then the object-level crack depth attributes could be extracted. The experimental results demonstrated that proposed method achieved average buffered Hausdorff scores of 94.39, Recall of 0.92 and F-value of 0.91 for crack detection on 30 real measured 3D asphalt pavement data. Furthermore, crack depth attributes can be extracted at different scales according requirements, the obtained location and depth attributes provide more comprehensive information for pavement maintenances.
关键词： Laser-scanning 3D,crack detection,crack attribute,tensor voting,OBIA
更新于2025-09-12 10:27:22
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Research on Edge Detection Algorithm Based on Line Laser Scanning
摘要： With the aim of obtaining the precise position of workpiece, it is necessary to detect the base hole during the automated manufacturing process of robotic drilling systems. In this paper, a detection method based on the line laser is presented to detect the base hole of large aviation parts in manufacturing and assembly. The 3-D point cloud data processing plays an important role during the detection process with a line laser. To extract the point cloud data effectively, an edge detection algorithm which includes a gradient-based edge extraction algorithm and an edge parameterization method is proposed. Then, the correlation analysis of the proposed algorithm is conducted. Finally, an industrial case is presented to illustrate the applicability and effectiveness of the proposed edge detection algorithm. The effects of varying the scan line spacing of the line laser are studied so as to meet the practical need of engineering application. The results indicate that the edge detection algorithm is applicable to the robotic drilling system, and it is reasonable and practicable to use the elliptic curve to parameterize the hole’s edge.
关键词： Line laser scanning,Correlation analysis,Base detection,Edge detection algorithm
更新于2025-09-12 10:27:22
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Assessing Fracture Surface Ductility by Confocal Laser Scanning Microscopy
摘要： Hitherto there is no generally accepted quantitative parameter which, on the one hand, would reliably characterize the ductility of the whole fracture surface, and, on the other hand, could be relatively quickly measured. This circumstance substantially affects the objectivity of the fractographic analysis which effectiveness is still strongly dependent on the experience and skills of an expert. Recent studies showed that the value of the normalized fracture surface area Rs can serve as the measure of the fracture surface ductility. This parameter can be evaluated by the quantitative confocal laser scanning microscopy (CLSM). In the present study we investigated the Rs value for the fracture surfaces of the low carbon steel specimens tested in the temperature range from 200 to -196 °C where the steel undergoes ductile-to-brittle transition accompanied by the alternation of the fracture mode from ductile to brittle. The temperature dependence of the Rs value is found to have a sigmoidal shape with the sharp drop in the range from 100 to -100 °C. It is demonstrated that the Rs is strongly correlated with the fracture surface appearance: the Rs decreases concurrently with increasing brittleness of the fracture surface.
关键词： quantitative fractography,normalized surface area,confocal laser scanning microscopy,low-carbon steel,fracture surface
更新于2025-09-12 10:27:22
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Aspects of Aerial Laser Scanning when exploring unknown archaeological sites (Case study)
摘要： Obtaining geographical information on the Earth's surface can be very costly and tedious. For this reason, remote sensing methods are increasingly used for these purposes, which allow the acquisition of terrain information via devices most often placed on board of aircraft or satellites. Currently, aircraft carriers are not used only for the acquisition of image data through aerial photography, but they can also carry on board other devices to obtain data of a different nature. This device can be an aerial laser scanner—LiDAR (Light Detection and Ranging) that scans the terrain and objects on the surface with a high precision. It is an active method of remote Earth survey based on the measurement of the distance between the object under investigation and the aircraft itself. The result of this process is a set of precise georeferenced points, which is referred to as a point cloud. By using spatial analyzes, it is possible to use various post-processing methods and it has applications in areas such as forestry, archeology, hydrology, etc. This paper is devoted to the use of Aerial Laser Scanning (ALS) for the purpose of archaeological research on the case study of the Molpír hillfort which is situated at the eastern foot of the Little Carpathians. For collecting the data, the PA-34 Seneca aircraft carrier was used and equipped with the Trimble Harrier 68i advanced mapping system. In the past, several archaeological surveys have been conducted in this area by using terrestrial measurements, however ALS has provided a different view and has enabled identification of sites which have not been previously identified and examined.
关键词： airborne laser scanning,archaeology,feature detection,hill-shading,remote sensing
更新于2025-09-12 10:27:22
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Nd:YAP laser in the treatment of dentinal hypersensitivity: An ex vivo study.
摘要： Purpose: The aims of this ex vivo study were to evaluate the effectiveness of the Nd:YAP laser in the treatment of dentin hypersensitivity, to compare the temperature rise during laser irradiation at three different dentine thicknesses, and to analyse the composition of the dentine-lased surface. Methods: A total of 33 teeth were used in this study. For scanning electron microscopy (SEM) observation, 24 teeth were transversely sectioned and divided into 4 groups: group A was irrigated with EDTA; group B was irradiated by Nd:YAP laser with 180 mJ energy/per pulse, 0.9 W average power, and 5 Hz frequency (power density [PD] = 229 W/cm2); group C was irradiated by Nd:YAP laser with 280 mJ energy/pulse, 1.4 W average power, and 5 Hz frequency (PD = 356 W/cm2); and group D was irradiated by Nd:YAP with 360 mJ energy/pulse, 1.8 W average power, and 5 Hz frequency (PD = 458W/cm2). Energy-dispersive spectroscopy (EDS) analysis was performed on the same teeth evaluated for SEM observations. For temperature increase evaluation performed with thermocouples, 9 teeth were transversely sectioned at 3 different thicknesses (3 for each group) of 1, 2, and 3 mm. Results: Statistical analysis showed significant changes in the diameter of the dentinal tubule orifices among all groups; EDS did not show modification of the Ca/P ratio. Temperature increase under irradiation exceeded 5.5°C only in the group D samples. Conclusions: This ex vivo study, based on temperature recording, SEM observation, and EDS analysis, demonstrated that Nd:YAP laser at a PD of 356 W/cm2, corresponding to an average power of 1.4 W, defines the best treatment for dentine hypersensitivity in terms of compromise between efficacy of the treatment and safety of the pulp.
关键词： dentinal hypersensitivity,energy-dispersive spectroscopy,thermal evaluation.,Nd:YAP laser,scanning electron microscopy
更新于2025-09-12 10:27:22
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Identification of trees and their trunks from mobile laser scanning data of roadway scenes
摘要： Trees along the roads are important assets, which need continuous assessment and maintenance. The mobile laser scanning (MLS) has been adopted as mainstream mapping technique for three-dimensional data acquisition along the roads. In this study, an automated method was developed to identify trees and their trunks from MLS data. A bottom-up search in two stages is adopted in the cylinders, which are formed by partitioning of normalized MLS data. Tree trunk is identified first based on linearity and data distribution homogeneity along lower section of object clusters lying near to the respective cylinder’s base centre. Then, crown of tree is retrieved for respective identified trunk using compactness index for circular or near-circular cross section of crown and its axial symmetry about trunk axis. The object cluster composed of trunk and crown both are identified as tree. The proposed method was tested and validated on MLS data of two different roadway test sites that were acquired at different point spacing. The results reveal that the performance of proposed method in these two sites in terms of average completeness, correctness, and F1 measure was 94.4%, 100%, and 97.1%, respectively. The correctness did not change in both sites and it was 100% and stable, which showed that none of the non-tree objects was falsely identified as tree and correctness in trees identification the test site complexity. The proposed method holds great potential for identifying trees from MLS data of various roadway site conditions, where shapes and sizes of trees in their 3D data get distorted due to occlusions, and partial overlap presents among objects. Furthermore, the proposed method was implemented in the graphics processing unit-based parallel computing framework and runtime was dramatically minimized on MLS datasets of two test sites.
关键词： tree identification,trunk detection,crown retrieval,roadway scenes,parallel computing,Mobile laser scanning
更新于2025-09-12 10:27:22
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New Method for Evaluating Surface Roughness Parameters Acquired by Laser Scanning
摘要： Quality evaluation of a material’s surface is performed through roughness analysis of surface samples. Several techniques have been presented to achieve this goal, including geometrical analysis and surface roughness analysis. Geometric analysis allows a visual and subjective evaluation of roughness (a qualitative assessment), whereas computation of the roughness parameters is a quantitative assessment and allows a standardized analysis of the surfaces. In civil engineering, the process is performed with mechanical profilometer equipment (2D) without adequate accuracy and laser profilometer (3D) with no consensus on how to interpret the result quantitatively. This work proposes a new method to evaluate surface roughness, starting from the generation of a visual surface roughness signature, which is calculated through the roughness parameters computed in hierarchically organized regions. The evaluation tools presented in this new method provide a local and more accurate evaluation of the computed coefficients. In the tests performed it was possible to quantitatively analyze roughness differences between ceramic blocks and to find that a quantitative microscale analysis allows to identify the largest variation of roughness parameters Raavg, Rasdv, Ramin and Ramax between samples, which benefit the evaluation and comparison of the sampled surfaces.
关键词： roughness parameters,laser scanning,hierarchical analysis,civil engineering,surface roughness
更新于2025-09-12 10:27:22
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Fruit detection in an apple orchard using a mobile terrestrial laser scanner
摘要： The development of reliable fruit detection and localization systems provides an opportunity to improve the crop value and management by limiting fruit spoilage and optimised harvesting practices. Most proposed systems for fruit detection are based on RGB cameras and thus are affected by intrinsic constraints, such as variable lighting conditions. This work presents a new technique that uses a mobile terrestrial laser scanner (MTLS) to detect and localise Fuji apples. An experimental test focused on Fuji apple trees (Malus domestica Borkh. cv. Fuji) was carried out. A 3D point cloud of the scene was generated using an MTLS composed of a Velodyne VLP-16 LiDAR sensor synchronised with an RTK-GNSS satellite navigation receiver. A re?ectance analysis of tree elements was performed, obtaining mean apparent re?ectance values of 28.9%, 29.1%, and 44.3% for leaves, branches and trunks, and apples, respectively. These results suggest that the apparent re?ectance parameter (at 905 nm wavelength) can be useful to detect apples. For that purpose, a four-step fruit detection algorithm was developed. By applying this algorithm, a localization success of 87.5%, an identi?cation success of 82.4%, and an F1-score of 0.858 were obtained in relation to the total amount of fruits. These detection rates are similar to those obtained by RGB-based systems, but with the additional advantages of providing direct 3D fruit location information, which is not affected by sunlight variations. From the experimental results, it can be concluded that LiDAR-based technology and, particularly, its re?ectance information, has potential for remote apple detection and 3D location.
关键词： Mobile terrestrial laser scanning,Agricultural robotics,Fruit detection,LiDAR
更新于2025-09-12 10:27:22