Laser Scanning Method Research Articles

Three-Dimensional Laser Scanning for Geometry Documentation and Construction Management of Highway Tunnels during Excavation

Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered.

INCREASE OF READABILITY AND ACCURACY OF 3D MODELS USING FUSION OF CLOSE RANGE PHOTOGRAMMETRY AND LASER SCANNING

Abstract. The development of laser scanning technology has opened a new page in geodesy and enabled an entirely new way of presenting data. Products obtained by the method of laser scanning are used in many sciences, as well as in archaeology. It should be noted that 3D models of archaeological artefacts obtained by laser scanning are fully measurable, written in 1:1 scale and have high accuracy. On the other hand, texture and RGB values of the surface of the object obtained by a laser scanner have lower resolution and poorer radiometric characteristics in relation to the textures captured with a digital camera. Scientific research and the goal of this paper are to increase the accuracy and readability of the 3D model with textures obtained with a digital camera. Laser scanning was performed with triangulation scanner of high accuracy, Vivid 9i (Konica Minolta), while for photogrammetric recording digital camera Nikon D90 with a lens of fixed focal length 20 mm, was used. It is important to stress that a posteriori accuracy score of the global registration of point clouds in the form of the standard deviation was ± 0.136 mm while the average distance was only ± 0.080 mm. Also research has proven that the quality projection texture model increases readability. Recording of archaeological artefacts and making their photorealistic 3D model greatly contributes to archaeology as a science, accelerates processing and reconstruction of the findings. It also allows the presentation of findings to the general public, not just to the experts.

Producing 3D city model with the combined photogrammetric and laser scanner data in the example of Taksim Cumhuriyet square

The purpose of this study is the analysis, comparison, optimization and complementation of spatial data, acquired by various methods, with various and different standards; in order to produce three dimensional urban models with adequate quality for city planners and urban planners. Pilot application area of the study was determined to be Taksim Cumhuriyet Square. In the end of accuracy comparison, data taken with terrestrial laser scanner method for the buildings covered with reflective materials and geometric data taken with terrestrial photogrammetry method on translucent buildings are used. The model, which was visualized in this way, became dynamic with animations. When the scale of application is considered, no need for DTM or DEM study has been seen necessary. In the conclusion of the study, the presumed hypothesis has been tested on a selected pilot implementation area and it was proved to be feasible. It is a method that can be used in other urban regions, too. The resulting model is a three dimensional square model, powered by terrestrial laser scanners which use real photogrammetric data. It is processed onto three dimensional maps in its real scale (1/1 scaled). It significantly contributes to the complimentary three dimensional model of Taksim Cumhuriyet Square and urban planners' micro-scale planning studies. The model presents all the technical information with integrated data sets which are necessary for permanent square arrangement.

Kinetics of T-cell receptor-dependent antigen recognition determinedin vivoby multi-spectral normalized epifluorescence laser scanning

Detection of multiple fluorophores in conditions of low signal represents a limiting factor for the application of in vivo optical imaging techniques in immunology where fluorescent labels report for different functional characteristics. A noninvasive in vivo Multi-Spectral Normalized Epifluorescence Laser scanning (M-SNELS) method was developed for the simultaneous and quantitative detection of multiple fluorophores in low signal to noise ratios and used to follow T-cell activation and clonal expansion. Colocalized DsRed- and GFP-labeled T cells were followed in tandem during the mounting of an immune response. Spectral unmixing was used to distinguish the overlapping fluorescent emissions representative of the two distinct cell populations and longitudinal data reported the discrete pattern of antigen-driven proliferation. Retrieved values were validated both in vitro and in vivo with flow cytometry and significant correlation between all methodologies was achieved. Noninvasive M-SNELS successfully quantified two colocalized fluorescent populations and provides a valid alternative imaging approach to traditional invasive methods for detecting T cell dynamics.

Development of a low-cost active 3D triangulation laser scanner for indoor navigation of miniature mobile robots

For miniaturized mobile robots that aim at exploring unknown environments, no-contact 3D sensing of basic geometrical features of the surrounding environment is one of the most important capabilities for survival and the mission. In this paper, a low-cost active 3D triangulation laser scanner for indoor navigation of miniature mobile robots is presented. It is implemented by moving both a camera and a laser diode together on the robot’s movable part. The movable part is actuated by a servo motor through a gear train to achieve ±90° scanning view angle. The software module includes image processing and data post-processing. 3D world coordinates are calculated from 2D image coordinates based on the triangulation principle. With a 3D laser scanning method, navigation algorithms for obstacle avoidance and gateway passing are proposed. Finally, experiments are conducted to validate performance of the scanner and to test the efficiency of the navigation algorithms.

Leaching of metal(loid)s from a construction material: Influence of the particle size, specific surface area and ionic strength

Construction materials are tested worldwide for a potential release of dangerous substances to prevent adverse effects on humans and biota. It is crucial to identify and understand the processes which are decisive for the release of hazardous substances. The current study compares the results of different test methods. Taking copper slag as model material, the influence of material particle size, eluant composition and ionic strength was tested. Ionic strength and salinity significantly influenced the release of metal(loid)s in the water phase. Furthermore, it was elucidated that colloids can cause methodological artefacts. The available specific surface area exhibited a positive correlation with the release of hazardous substances. The specific surface areas of materials were determined by the Brunauer, Emmett and Teller model (BET) and four other methods. The aluminium foil method showed the best results with regard to the statistical uncertainty, compared to a 3D laser scanning method. With help of the roughness factor λ it is possible to compare the results from surface area measurements with different material particle sizes (0–250mm). This comparability offers the potential to match the release of metal(loid)s from laboratory studies with field applications and catchment area calculations/modelling, based on the release per m2.

Use of laser scanning to evaluate turbot (Scophthalmus maximus) distribution in raceways with different water velocities

Fish distribution can be a reliable indicator of husbandry conditions but, as happens with other behavioral parameters, it is not easy to assess with objectivity and repeatability. Here, we used a laser scanning method to monitor the distribution variations of a turbot (Scophthalmus maximus) population in a tank under different water velocity treatments, using (1) two uniform water velocities throughout the rearing unit, by changing the water depth but keeping the water flow; (2) different water velocities inside the rearing unit, which allowed the fish to choose a preferred zone; and (3) baffles to create a higher velocity and turbulence above and below them. Preliminary results on water velocity preferences or tolerance for 22-cm turbot determined that velocities between 0.33 and 0.46BLs−1 promoted a homogenous turbot distribution, but that when the fish could choose, they avoided swimming against water flows over 0.58BLs−1. With a velocity over 0.98BLs−1, turbot no longer appeared to be able to maintain their position. We also tested the viability of the method to estimate the total biomass of turbot in a high-density tank (from 280 to 320 percentage of coverage area [PCA]). The resulting coefficient of variation between samplings was lower than 10%. The laser scanning has proven to be a useful tool to monitor flatfish distribution and to estimate the total biomass in flatfish culture, and it offers several advantages: (1) it is objective and non-intrusive, thus minimizing stress; (2) it can be used with a high stocking density; (3) it analyzes biomass population; and (4) it can be adapted to existing commercial facilities.

Reliability of a PowerPoint Method for Wear Measurement After Total Hip Arthroplasty: A Retrieval Study Using 3-Dimensional Laser Scanning

The purpose of this study was to evaluate the reliability of the PowerPoint (PP) (2007 Version; Microsoft, Redmond, Wash) method for measuring polyethylene liner wear after total hip arthroplasty. Seventeen retrieved polyethylene liners were included in this study. Wear volumes were calculated using the PP, the Dorr and Wan, and 3-dimensional (3D) laser scanning methods. Spearman correlation coefficients for wear volume results indicated strong correlations between the PP and 3D laser scanning methods (range, 0.89-0.93). On the other hand, Spearman correlation analysis revealed only moderate correlations between the Dorr and Wan and 3D laser scanning methods (range, 0.67-0.77). The PP method can be used to monitor linear wear after total hip arthroplasty and could serve as an alternative method when computerized methods are not available.

Aggregate Surface Areas Quantified through Laser Measurements for South African Asphalt Mixtures

For several decades, efforts have been made by engineers and researchers in road and airfield pavements and railroads to develop methods/procedures for accurate quantification of aggregate shape and packing properties. The difficult part of the process has been the fact that aggregate particles have irregular and nonideal shapes. New research capabilities, including laser-based technology, can effectively address the difficulties associated with aggregate shape measurements to optimize asphalt mix design. This paper introduces the use of a three-dimensional (3D) laser scanning method to directly measure the surface area of aggregates used in road pavements in South Africa. As an application of the laser-based measurements, the asphalt film thicknesses of five typical South African mixtures were calculated and compared with the film thicknesses calculated from traditional methods. Based on the laser scanning method, new surface area factors were developed for coarse aggregates used in the asphalt mixtures. Overall, the study demonstrated applicability of 3D laser scanning method to characterize coarse aggregates.

Statistical characteristics of two-phase gas-liquid flow in a vertical microchannel

This paper presents an experimental study of the structure of an upward gas-liquid flow in a vertical microchannel with a cross-sectional dimension of 0.67 × 2.00 mm and a length of 0.5 m. The tests were performed in the ranges of reduced rates of nitrogen 0.04–11.00 m/sec and water 0.07–0.41 m/sec. Using the method of two-beam laser scanning, we identified the main flow regimes (slug-bubble, slug, transient, emulsion, and annular) and determined the statistical characteristics of the two-phase flow. A map of flow regimes was constructed, the dependence of slug velocity on the reduced mixture velocity was obtained, and the friction factor for an upward gas-liquid flow in a microchannel was measured.

Study on the Measurement Method of Soil Surface Roughness

Based on the determination method of the comprehensive domestic and international surface roughness, by the method of indoor artificial rainfall, the determination of soil surface roughness had been studied from the measurement accuracy, time-consuming and resolution. The results showed that the laser scanner method was the best to determine the surface roughness, followed by pin meter method, the roller chain meter method, and the ruler was the worst. The results of determination had the better correlation between the laser scanner method and the roller chain meter method before rainfall, however they had poor correlation after rainfall. They had the better correlation between the laser scanner method and pin meter method both before rainfall and after rainfall. And on this basis, the relationships were established among the different methods. The results provide theory basis for the further study on soil surface roughness. At the same time, it would serve for harnessing soil and water loss of the slope farmland in Loess Plateau.

Structural analysis of the Roman Bibei bridge (Spain) based on GPR data and numerical modelling

There are many ancient masonry arch bridges still in use within the actual transportation. Some of these bridges are in need of special attention because they are subject to potentially destructive conditions, such as increased traffic loads and intense vibrations produced by their new functions, and these stresses are compounded by their age. To preserve these functional structures, structural assessment is necessary or, at least, highly recommended. However, many of the details of these structures are underground and are therefore hidden from view. In recent decades, ground-penetrating radar (GPR) has shown potential for internal bridge evaluation. The Roman Bibei bridge (Spain) was surveyed with GPR to analyse its inner state of conservation. The GPR survey was conducted using 250 and 500 MHz antennas. The interpretation and analysis of the GPR data were supported by finite-difference time domain numerical modelling based on the precise external geometry provided by three-dimensional laser scanning methods. Both real and synthetic results reveal that GPR evaluation provides unknown structural details and possible modifications over time. The internal ring stone thickness was also measured, which represents valuable information for engineers to perform an exhaustive assessment of the load carrying capacity of the bridge.

CAD/CAM-assisted breast reconstruction

The application of computer-aided design and manufacturing (CAD/CAM) techniques in the clinic is growing slowly but steadily. The ability to build patient-specific models based on medical imaging data offers major potential. In this work we report on the feasibility of employing laser scanning with CAD/CAM techniques to aid in breast reconstruction. A patient was imaged with laser scanning, an economical and facile method for creating an accurate digital representation of the breasts and surrounding tissues. The obtained model was used to fabricate a customized mould that was employed as an intra-operative aid for the surgeon performing autologous tissue reconstruction of the breast removed due to cancer. Furthermore, a solid breast model was derived from the imaged data and digitally processed for the fabrication of customized scaffolds for breast tissue engineering. To this end, a novel generic algorithm for creating porosity within a solid model was developed, using a finite element model as intermediate.

Comparison of Tacheometry and Laser Scanning Methods for Measuring the Quarry in Jakubčovice Nad Odrou / Porovnání Tachymetrie A Laserového Skenování Při Zaměření Části Lomu V Jakubčovicích Nad Odrou

Abstract The presented this method is more efficient for surveying a site. Part of this is the calculation of the volumes of excavated muck using 3D models and their comparison. The comparison of the measurements of part of the quarry in Jakubčovice nad Odrou using the tacheometry and laser scanning techniques was performed. The final assessment was in favour of the laser scanning method which provides capturing the entire object surface with a chosen level of detail compared to the tacheometry method, in which only characteristic points of the measured object, such as edges, are captured.

Errata: Analysis of a head-mounted display-type multifocus display system using a laser scanning method

Errata: Analysis of a head-mounted display-type multifocus display system using a laser scanning method

Structural geometry and evolution of releasing and restraining bends: Insights from laser-scanned experimental models

Experimental modeling is used to study the geometry and evolution of structures and related secondary faults along releasing bends and offsets and restraining bends on strike-slip faults. The controls of the relative positions of adjacent strike-slip faults on the geometry of the structures and the difference in geometries between bends and offsets are investigated. A new method of laser scanning is used to map the geometry and evolution of the structures and related faults. The models show that oblique releasing bends connecting approaching faults result in spindle-shaped basins, whereas transverse bends result in more S-shaped or rhomboidal basins. Offsets result in the distribution of strain over a wider area and a larger number of faults compared with preexisting bends, which result in fewer well-defined basin-bounding faults. Secondary faults include R, R, and Y Riedel shears near the main strike-slip faults and oblique normal faults in the center of the basin. Fault patterns exhibit en echelon geometries with a progressive step down into the deepest parts of the basin. Symmetric, asymmetric, and double basins may form in any of the structural settings, depending on the slip distribution among faults on the basin margins. For restraining bends, oblique (45) bends connecting approaching faults result in spindle-shaped uplifts, whereas transverse or oblique (135) bends connecting overlapping faults result in more rhomboidal or rectangular uplifts. The fold trends are at increasingly higher angles with the strike faults for transverse and oblique (135) bends. Secondary faults include en echelon reverse faults, which typically form along the steep limbs of asymmetric uplifts, normal faults, which are transverse or oblique to the axis of the structure, and R, R, and Y Riedel shears near the main strike-slip faults. The aspect ratios of the basins and uplifts increase with increasing displacement on the strike-slip faults. The results of these models can be used to interpret the structural and fault geometries in surface and subsurface structures formed along strike-slip faults.

Measurement of the state of tunnel lining and floor by Full-Rotating Laser Scanning Method

Measurement of the state of tunnel lining and floor by Full-Rotating Laser Scanning Method

휴대폰용 금속 프론트 케이스의 프레스 성형공정에서 프레임의 형상오차 저감을 위한 연결부 형상설계

The metal front case of a mobile phone is manufactured by press forming and welding of thin metal sheets. Twisting of the frame after the forming process is one of main obstacle for the assembly with reinforcement by welding. This study introduces a method preventing twisting of the metal front case frame in press forming. The spring-back after forming produces twisting of the frame, which leads to a low structural stiffness. To reduce twisting, connectors are required to reinforce the structural stiffness of the frame. In this study, the twisting profile is evaluated using a finite element(FE) analysis for various connector shapes. The actual connector shape is determined by minimization of the frame twisting within the tolerance of the FE-analysis. To verify the validity of the proposed blank shape, a forming experiment is performed and the twisting profile is measured using a 3D laser scanning method. The dimensional accuracy is found to be within the tolerance and in good agreement with the FE-analysis.

Analysis of a head-mounted display-type multifocus display system using a laser scanning method

We developed a head-mounted display (HMD)-type multifocus display system using a laser-scanning method to provide an accommodation effect for viewers. This accomplishment indicates that providing a monocular depth cue is possible through this multifocus system. In the system, the optical path is changed by a scanning action. To provide an accurate accommodation effect for the viewer, the multifocus display system is designed and manufactured in accordance with the geometric analysis of the system's scanning action. Using a video camera as a substitute for the viewer, correct focus adjustment without the scanning action problem is demonstrated. By analyzing the scanning action and experimental results, we are able to illustrate the formation of a viewpoint in an HMD-type multifocus display system using a laser-scanning method. In addition, we demonstrate that the accommodation effect could be provided independent of the viewing condition of the viewer.

A new method to orient 3-dimensional computed tomography models to the natural head position: a clinical feasibility study.

The purpose of this study was to evaluate the clinical feasibility of a new method to orient 3-dimensional (3D) computed tomography models to the natural head position (NHP). This method uses a small and inexpensive digital orientation device to record NHP in 3 dimensions. This device consists of a digital orientation sensor attached to the patient via a facebow and an individualized bite jig. The study was designed to answer 2 questions: 1) whether the weight of the new device can negatively influence the NHP and 2) whether the new method is as accurate as the gold standard. Fifteen patients with craniomaxillofacial deformities were included in the study. Each patient's NHP is recorded 3 times. The first NHP was recorded with a laser scanning method without the presence of the digital orientation device. The second NHP was recorded with the digital orientation device. Simultaneously, the third NHP was also recorded with the laser scanning method. Each recorded NHP measurement was then transferred to the patient's 3D computed tomography facial model, resulting in 3 different orientations for each patient: the orientation generated via the laser scanning method without the presence of the digital orientation sensor and facebow (orientation 1), the orientation generated by use of the laser scanning method with the presence of the digital orientation sensor and facebow (orientation 2), and the orientation generated with the digital orientation device (orientation 3). Comparisons are then made between orientations 1 and 2 and between orientations 2 and 3, respectively. Statistical analyses are performed. The results show that in each pair, the difference (Δ) between the 2 measurements is not statistically significantly different from 0°. In addition, in the first pair, the Bland-Altman lower and upper limits of the Δ between the 2 measurements are within 1.5° in pitch and within a subdegree in roll and yaw. In the second pair, the limits of the Δ in all 3 dimensions are within 0.5°. Our technique can accurately record NHP in 3 dimensions and precisely transfer it to a 3D model. In addition, the extra weight of the digital orientation sensor and facebow has minimal influence on the self-balanced NHP establishment.