Search Results (1,276)

The application of information systems to the documentation and representation of historical–architectural heritage is currently the focus of research, experimentations, and innovations increasingly geared towards awareness, management, and conservation processes. This involves addressing unresolved challenges arising from the effort of translating the inherent complexity of heritage into knowledge that can be applied to monitoring, conservation, informative, cross-relational, and interdisciplinary actions. Processes involving data classification, segmentation, and semantic association for high-level knowledge clustering, exploiting Artificial Intelligence algorithms, are emerging as a potential—albeit ambivalent—aid in the management of digital information sources. The paper explores some State of the Art procedures in the field and ongoing applied research with a particular focus on the concept of adaptive data management, leveraging parametric modeling and applications within 3D point cloud data for the recognition of surface features and diagnostic purposes. The reconciliation of information between the point cloud segmented through Artificial Intelligence algorithms and the HBIM model starts from heritage building laser scanner and photomodeling datasets, analyzing materials and state of conservation features. The experimentation is focused on a reverse approach—the so-called “HBIM-to-Cloud”—with the aim of generating an enriched information cloud defined by the surfaces of the parametric model. Full article

Finite-length raster scanning can cause endpoint over-ablation, whereas repeated scanning along a fixed direction can reinforce directional bottom textures. In this study, skywriting-based synchronized gating was combined with four-direction orthogonal cross-hatch scanning to fabricate square micro-holes on 316L stainless steel using a picosecond laser. Scanner acceleration and deceleration occurred outside the target region, and laser output was restricted to the constant-velocity segment. The local height variation at the line start decreased from approximately 8.0 to 1.3 μm. At a nominal processing area of 320 μm × 320 μm and a cumulative count of 140 full-area scans, four-direction scanning produced a bottom-surface S_a of 0.325 μm, 52.3% lower than that obtained by unidirectional raster scanning. It also yielded lower S_a and S_q values than continuous serpentine raster and continuous square-spiral scanning. Increasing the scan count from 84 to 532 increased the machining depth from 22.4 to 135.4 μm, with an approximately linear relationship over the tested range. However, bottom roughness and bottom-area shrinkage increased with depth. These results demonstrate that synchronized gating and directional alternation improve endpoint consistency and average bottom uniformity, while depth extension requires balancing removal depth against bottom quality. Full article

Virtual trial assembly (VTA), an alternative to physical trial assembly, has been used in many projects owing to its advantages of low time consumption and low cost. However, the existing methods based on the terrestrial laser scanner struggle with noise, incomplete boundaries, and arbitrary initial poses, making them impractical for steel members of long-span suspension bridges with bolted connections. Therefore, this study proposes a novel method combining robust circle fitting and matching constrained based on multiple features. Firstly, alpha shape and DBSCAN algorithms precisely extract hole boundaries from unstructured point clouds. Secondly, a Huber loss model optimized via Iteratively Reweighted Least Squares (IRLS) extracts hole centers, effectively overcoming measurement noise and local defects. Thirdly, integrating global polar coordinates and local topological descriptors establishes reliable correspondences without prior pose information. Finally, singular value decomposition calculates the optimal rigid transformation matrix for spatial alignment. The results show the novel method consistently outperforms common Least Squares (LS), Pratt, Taubin, and Random Sample Consensus (RANSAC) algorithms regarding feature extraction stability. Evaluated exclusively upon the specific point cloud dataset acquired in this study, the proposed algorithm achieved a minimal internal registration Root Mean Square Error (RMSE) of 0.148 mm and a Mean Absolute Error (MAE) of 0.076 mm. These specific algorithmic residuals confirm highly reliable relative computational consistency for the tested bridge components, though extensive validations remain necessary for generalized field conditions. Full article

This study investigated the influence of circumferential welding position and process parameters on bead geometry during multi-pass orbital gas tungsten arc welding (GTAW) of SUS304 stainless-steel pipes. Three-dimensional surface profiles were measured using a laser line scanner at the top (12H, −45° to 45°) and bottom (6H, 135° to 225°) circumferential regions. The incremental bead height and width of Passes 1 and 2 were quantitatively evaluated after excluding the first and last 10% of the measured region to minimize edge effects. Under identical root-pass conditions, the average Pass 1 bead height at 6H was 9.6% greater than that at 12H, whereas the bead width was 3.3% smaller. After Pass 2, the height difference increased to 12.0%, while the width difference remained small at 2.4%. Primary current, wire feed speed, and travel speed exhibited position-dependent effects on bead formation. Primary current affected the balance between vertical buildup and lateral spreading, wire feed speed consistently influenced bead width, and travel speed strongly affected bead buildup through changes in heat input, filler deposition per unit length, and molten-pool residence time. The greater reinforcement at 6H was attributed to gravity-dependent molten-metal accumulation during successive deposition. Interpolation of the primary-current experiments predicted that approximately 173 A at 12H and 175.5 A at 6H would produce comparable Pass 2 geometries of approximately 1.62 mm in height and 6.57 mm in width. These results demonstrate that circumferential bead uniformity can be improved through position-dependent parameter adjustment rather than identical welding conditions around the pipe circumference. Full article

Screws are critical mechanical components, and their geometric accuracy directly determines the performance and reliability of mechanical systems. However, conventional contact-based inspection methods are time-consuming and limited to sparse sampling. Existing non-contact optical techniques often suffer from insufficient edge localization accuracy due to discrete point spacing. To address these challenges, this paper proposes a vision-guided point cloud refinement measurement method. The system integrates a laser scanner with a camera, where the laser scanning serves as the primary channel for acquiring three-dimensional point clouds, and the vision system provides high-resolution thread edge positions through sub-pixel localization and interpolation. A joint 2D-3D registration procedure is established to transfer the 2D sub-pixel edge localization precision to the corresponding 3D points, effectively correcting the spatial positions of thread crests. A coarse-to-fine processing pipeline is then applied, encompassing PCA-based principal axis alignment, Fourier transform-based coarse pitch estimation, and Gaussian pyramid-based multi-resolution refinement, to extract the pitch from the refined point cloud. Experimental validation on a real screw specimen confirms that the proposed method achieves a pitch measurement error of 0.0423 mm, demonstrating performance comparable to the pure vision-based method. It can provide a reliable solution for high-precision screw thread inspection. Full article

Due to the cross-section characteristics of rectangular pipe jacking, the “soil-carrying effect” of overlying soil migration with the pipeline is prone to occur during jacking in shallow strata, resulting in a sharp increase in jacking resistance and large deformation of the strata. In this paper, a visual similarity model test of the soil-carrying effect is carried out for shallow buried large-section rectangular pipe jacking. The experiment innovatively combines VIC-3D digital image correlation technology, a 3D laser scanner and a thin-film pressure sensor to monitor the displacement of deep soil, surface heave and pipe resistance in an all-round and high-precision way. The influence of the overburden ratio and pipe–soil friction coefficient on the evolution of back soil was systematically studied. The results show that the evolution of the soil-carrying effect presents the three-stage characteristics of ‘elasticity-slip-strengthening’, and the smaller the overburden ratio, the larger the friction coefficient. And the smaller the critical displacement of the back soil, the more severe the formation disturbance. Based on the principle of mechanical balance, this paper puts forward the theoretical prediction model of the whole soil-carrying effect, deduces the critical friction coefficient and the critical jacking mileage, and compares it with the experimental results, which provides a scientific basis for the optimization of construction parameters and safety control of shallow buried rectangular pipe jacking. Full article

This study examines the relevance of Terrestrial Laser Scanning (TLS) for documenting and reconstructing architectural heritage elements that have partially or completely disappeared over time, using the remains of the service staircase of the Infantado Palace (Guadalajara) as a case study. Approaches based solely on historical plans cannot verify their reliability without physical evidence for contrast. Based on a critical analysis of existing historical plans and an updated survey using a Terrestrial Laser Scanner (FARO Focus 3D S120), a reconstructive hypothesis is proposed for the 16th-century service staircase. The 3D scanning revealed initial evidence of the previous structure’s existence; within the Palace’s historical–constructive context (15th–16th centuries), the study analyzes the 19th-century floor plans by the Madrid School of Architecture and the Geographic and Statistical Institute, evaluating their correspondence with current spaces. The methodology integrates 3D point cloud surveying, documentary analysis, metric comparison, and the development of an HBIM (Heritage Building Information Modeling) model as the tool through which the reconstruction proposal is materialized and adjusted to empirical evidence, contrasting historical sources with physical evidence. The results reveal discrepancies between historical plans and a previously undocumented constructive reality, confirming the advantage of empirical contrast over documentary analysis. Consequently, the survey made it possible to precisely locate the elements needed to propose the reconstruction of the service staircase. The originality of this study lies in shifting TLS from mere graphic documentation toward the hypothetical reconstruction of disappeared elements, extending its use to research on the historical spatial functioning of buildings. Full article

Accurate stability assessment of potentially unstable rock blocks is essential for the safe construction and operation of hydropower infrastructure. This study applies a comparative limit-equilibrium workflow to a single, well-characterized sliding-type rock block (156.7 m³) bounded by three discontinuities (J1 250°/35°, J2 305°/75°, J3 215°/80°) on a hydropower station slope; discontinuity attitudes were measured with a geological compass and a terrestrial three-dimensional laser scanner, and the slope surface was reconstructed by UAV photogrammetry. A common, fully documented parameter set is used by a conventional two-dimensional method, a block-dividing limit-equilibrium method, and a three-dimensional residual-thrust method with moment equilibrium. With the site-suggested shear strengths and the lower-bound cohesion as the representative value, the block-dividing method gives factors of safety of 1.169, 1.063 and 0.903 under natural, heavy-rainfall and seismic conditions at optimal azimuths of 265.8°, 266.3° and 269.1°; the corresponding two-dimensional values are 1.037, 0.904 and 0.729, and the residual-thrust values are 1.497, 1.324 and 1.049. The block-dividing factors are 12.7–23.9% above the two-dimensional profile, whereas the residual-thrust result lies a further 16–28% higher (44–47% above the two-dimensional profile); this over-estimate is traced to the steep (75°, 80°) lateral release planes and to a mesh- and lambda-sensitive column solution, and is therefore non-conservative. A cohesion sensitivity analysis with fixed friction angle shows that the factor varies by 51–57% across the suggested cohesion interval. Under code-specified targets of 1.30/1.20/1.05, horizontal anchorage requires 366/427/566 kN versus 1150/1470/1413 kN for a perpendicular-to-slope layout, so a horizontal scheme of about 0.6 MN is adopted. Finite-element validation and field piezometric/displacement monitoring data, unavailable for this block, are identified as required future work. Full article

This article presents an analysis of the effect of an anti-reflective layer on the measurement process using the 3D GOM (ATOS II Triple Scan; currently ZEISS) optical scanner for spherical elements manufactured using four additive methods: PolyJet Modeling (PJM), Digital Light Processing (DLP), Melted Extrusion Modeling (MEM), and Direct Metal Laser Sintering (DMLS). The research focused on analyzing the effect of the anti-reflective (AR) layer on changes in numerical data and on differences that define the shape of the measured elements. It was noted that models made of light-cured resin (EC100 (DLP) and RGD720 (PJM)) were characterized by AR layer absorption, which affected the measurement results. The use of the AR layer also increases the number of points for which a fitted sphere is created in the optical scanner software for shape analysis of the research models. The application of the AR layer also affects the average dimensional deviations (relative to the MB1 and MB2 research models), most significantly for models made using the PJM and MEM methods (approx. 0.02 mm), and least significantly for models made using the DMLS method (approx. 0.004 mm). The conducted research, presented measurement results, analyses, and conclusions, will help predict the impact of using the AR layer on the measurement process and the accuracy of the obtained results of measured geometric parameters during 3D GOM (ATOS II Triple Scan) optical measurements of models made of selected materials. Full article

Construction material identification is important for automated construction monitoring, digital twin generation, and building information modelling. Terrestrial laser scanning (TLS) provides dense geometric information together with LiDAR intensity measurements; however, reliable material discrimination remains challenging because intensity is affected by acquisition geometry and surface texture may vary depending on the spatial scale at which it is characterised. This study proposes a TLS-only machine-learning framework combining a reflectance-related intensity–geometry regression descriptor with multiscale geometric roughness features. Plane-residual roughness and normal-variation roughness were calculated using local cube neighbourhoods with side lengths of 0.10, 0.20, and 0.30 m. To avoid ambiguity associated with surface-normal orientation, the normal-variation descriptor was calculated using orientation-invariant angular differences between neighbouring surface normals. The training dataset was balanced using distance-stratified random undersampling, while the held-out test dataset retained its original class distribution. FLAML was used for automated model selection and hyperparameter optimisation using three-fold cross-validation with macro F1-score as the optimisation metric. The final stacking classifier achieved an overall accuracy of 90.44%, balanced accuracy of 87.42%, and macro F1-score of 87.85% on 1,296,822 held-out test points. The held-out test data were acquired from different scanner positions and spatially distinct material regions from those used for training, with no shared point samples; however, both datasets originated from the same general study area, and broader cross-site generalisation therefore requires further independent validation. Most material classes showed strong discrimination, although Carpet remained challenging because of confusion with Asphalt. The results demonstrate the potential of combining TLS-derived radiometric information with multiscale geometric surface descriptors for construction material classification without relying on RGB colour information. Full article

Surface normal estimation is a fundamental step in many applications, including robotics, manufacturing inspection and quality control. Reliable surface normal information is essential for accurate surface reconstruction, defect detection, and geometric analysis. In this paper, different approaches for estimating surface normal vectors from point cloud data are investigated, with particular focus on their suitability for generating ground-truth surface normals. Such ground-truth measurements are required to evaluate and validate surface normal estimation techniques used in practical metrology and 3D sensing systems in accordance with established surface texture standards such as ISO 25178. The analysis focuses on methods based on neighbourhood clustering followed by a surface normal fitting procedure. In addition, the influence of point cloud noise on the accuracy and stability of the estimated normals is systematically studied. By comparing the performance of different estimation strategies under different noise conditions, their suitability for generating reliable reference surface normals is investigated. The results demonstrate how point cloud characteristics and noise levels affect the robustness of surface normal estimation and highlight the advantages and limitations of commonly used approaches. The proposed analysis provides practical guidance for selecting appropriate methods when generating ground-truth surface normals for the validation of optical and geometric measurement systems. To show that the studied approaches can be used for surface normal estimation independent of metrology equipment, they are applied to the point clouds acquired from laser scanners, confocal optical measurement equipment, coherence scanning interferometers, and fringe projection systems with a variety of test objects. The results show that the studied approaches can estimate the surface normals. Highly accurate surface normal estimation may ease surface texture studies. The findings contribute to improving the reliability of point cloud analysis and surface normal estimation in manufacturing metrology and related applications. Full article

This study investigates the deformation of plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) on uniform cushions and flat-rounded gravel cushions using a self-developed testing apparatus for GMB deformation and a three-dimensional (3D) laser scanner. Based on the principle of square voids equivalent to circles, the void width–depth ratio was adopted to quantify voids within granular cushions. The models between strain and void width–depth ratio, as well as gradation parameters, were established. The gradation parameters of flat-rounded gravel cushions satisfying the deformation requirements were determined for GMBs as anti-seepage materials in basins of pumped storage power stations. The results demonstrate that the areal strain of the PVC-P GMB is consistently greater than its linear strain for uniform cushions. From the perspective of engineering safety, the areal strain is recommended to characterize the deformation of PVC-P GMBs. The GMB areal strain on flat-rounded gravel cushions exhibits an allometric function with the width–depth ratio and non-uniformity coefficient, and an Exp2P function with the maximum limiting particle size, with all determination coefficients exceeding 0.99. Based on the areal strain less than 20% of its elastic strain threshold, the granular cushion should satisfy a non-uniformity coefficient in the range of 15.3 to 20.7, and the maximum limiting particle size is between 4.75 and 23.54 mm, the PVC-P GMB can maintain elastic deformation behavior, which extends its service life in practical engineering. These findings contribute to a deeper understanding of the local deformation behavior of PVC-P GMBs on cushion layers. The gradation parameters satisfying the deformation requirements for particle cushion layers provide technical guidance for cushion layer design for the application of PVC-P GMBs in pumped storage power stations. Full article

Three-dimensional comparative descriptions of the ossa cranii across representatives of the Camelidae, Giraffidae, and Bovidae remain limited despite their relevance to comparative veterinary anatomy and clinical practice. Given the distinct structural variations and functional adaptations of these families, a descriptive comparison of ossa cranii morphology is needed to advance anatomical knowledge and establish species-specific reference data. This study compared the principal ossa cranii of camel, giraffe, cattle, sheep, and goat to identify conserved anatomical features and species-specific adaptations. High-resolution three-dimensional digital skull models were generated with a Creality Raptor blue laser scanner and processed using 3D Slicer (Version 5.6.2). Due to marked interspecific differences in skull size and cranial capacity, quantitative morphometric analyses were not feasible; therefore, comparisons were based on qualitative gross anatomical evaluation of the os occipitale, os sphenoidale, os parietale, os temporale, os frontale, os pterygoideum, os ethmoidale, and os vomer. Although the overall organization of the ossa cranii was conserved, distinct species-specific adaptations were identified. Camels exhibited a prominent crista sagittalis externa, a broad nuchal surface, an elongated os vomer, and the absence of the tuber faciale and processus cornualis. Giraffes showed well-developed ossicones, a pronounced frontoparietal prominence, enlarged frontal sinuses, modified occipital condyles, and elongated ethmoid and vomer bones. Bovids were distinguished by horn-related structures, frontal sinus configuration, the processus jugularis, bulla tympanica, and foramen supraorbitale. Ossa cranii morphology reflects both anatomic relationships and functional adaptations associated with feeding behavior, head posture, and muscle attachment. These findings provide comparative anatomical reference data that support veterinary anatomy education, diagnostic imaging, species-specific surgical planning, and future studies in functional morphology and paleontology. Full article

Background: Sexual dimorphism in tooth size has been assessed on radiographs, dental casts, two-dimensional image analysis, and linear measurements are evaluated in two dimensions. These approaches evaluate isolated dimensions and may not adequately represent the three-dimensional complexity of tooth morphology. This study compared conventional odontometric measurements, centroid-based size assessments, and principal component-derived multidimensional size variables to determine whether overall tooth size exhibits sexual dimorphism. Methodology: A total of 120 dental casts (60 males and 60 females) were digitized using a laser surface scanner. Anatomical and geometric landmarks were identified on three-dimensional tooth models using 3D Slicer software. Mesiodistal, buccolingual, and diagonal dimensions were calculated from landmark coordinates, and two- and three-dimensional centroid sizes were derived. Principal component analysis was used to generate integrated multidimensional size variables. Sex differences were evaluated using independent Student’s t-tests, two one-sided tests (TOST) for equivalence, and random-effects meta-analysis. Results: Principal component analysis showed that conventional odontometric measurements and centroid sizes represented a common multidimensional size construct, explaining 79.1–91.3% of the variance across most tooth types. Centroid size demonstrated the highest component loadings, and principal component-derived variables correlated strongly with centroid size (r = 0.945–0.994; p < 0.001). No significant sex differences were observed for any principal component-derived size variable (p > 0.05). Equivalence testing and pooled meta-analysis demonstrated practical and statistical equivalence between males and females across principal component-derived variables, centroid sizes, and conventional odontometric measurements (all TOST p < 0.001). Conclusions: Conventional odontometric measurements, centroid sizes, and principal component-derived variables capture a common multidimensional construct of tooth size. Although isolated dimensions may differ, overall tooth size is practically equivalent between males and females. Full article

Automated three-dimensional (3D) mapping with a survey-grade terrestrial laser scanner (TLS) is the canonical instance of robotic stop-and-scan light detection and ranging (LiDAR) mapping: the mobile platform must remain stationary for minutes per scan, so the environment must be covered with as few scans as possible. Where to stop hinges on a coverage model predicting what a scan pose will observe. The conventional isotropic-disk model counts every free cell within sensing range as covered—including cells behind walls—and, therefore, skips scans that genuine observation requires. We replace the disk with a ray-cast visibility region computed on the robot’s live two-dimensional (2D) occupancy map, admitting only cells in direct line of sight; define a line-of-sight (LOS) coverage metric over mapped free space and drive a marginal-gain scan/skip rule embedded in frontier exploration. The planner thus performs 2D scan-station placement for subsequent 3D mapping. In a controlled paired ablation in simulation, the visibility rule raises LOS coverage from about 77% to 84–85% for one to two additional scans, and it also outperforms a disk baseline governed by the identical marginal-gain rule, isolating the coverage model itself as the decisive factor. In a fully autonomous on-hardware comparison in an industrial test room, with each rule driving a mobile platform carrying a Leica BLK360 G1, the visibility rule raised LOS coverage from 77.6% to 92.1%; every visibility run’s scans registered offline at survey grade (4–5 mm bundle error, 84–88% overlap), whereas disk runs yielded at best a single-link network and once a single unregistrable scan. The results indicate that, for the room-scale indoor environments studied, occlusion-aware visibility is a sounder basis than Euclidean proximity for stop-and-scan placement. Full article