Application Of Laser Scanning Research Articles

A new approach to recording and monitoring wet-preserved archaeological wood using three-dimensional laser scanning

The analysis and preservation of organic materials preserved within wetland environments represents one of the most costly parts of any post-excavation strategy. This paper outlines the application of high-resolution terrestrial laser scanning to one class of preserved material, worked archaeological wood. Scanning allowed the recording of the artefacts in three dimensions and the identification of features such as toolmarks. Features can be measured and volumetrically modelled within the digital environment, which may not always be possible for these often fragile materials using conventional techniques. Repeat scanning of the artefacts provided an opportunity to use comparative analysis software to investigate changes in the morphology of artefacts under contrasting conditions of short-term storage. The results suggest that immersion in water results in the least deterioration, whereas both freezing and air-drying caused distortion and degradation. This paper demonstrates that laser scanning provides a viable alternative post-excavation method for the recording, analysis and long-term ‘virtual archiving’ of organic archaeological materials, which may be more cost-effective in some instances than other methods of preservation.

A 2-DOF Circular-Resonator-Driven In-Plane Vibratory Grating Laser Scanner

In this paper, we present the design, modeling, fabrication, and measurement results of a microelectromechanical systems (MEMS)-based in-plane vibratory grating scanner driven by a two-degree-of-freedom (2-DOF) comb-driven circular resonator for high-speed laser scanning applications. Diffraction grating driven by a 2-DOF circular resonator has the potential to scan at large amplitudes compared with those driven by a one-degree-of-freedom (1-DOF) comb-driven circular resonator or a 2-DOF electrical comb-driven lateral-to-rotational resonator. We have demonstrated that our prototype device, with a 1-mm-diameter diffraction grating is capable of scanning at 20.289 kHz with an optical scan angle of around 25 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> . A refined theoretical model with fewer assumptions is proposed, which can make the prediction of dynamic performance much more accurate.

Application and statistical analysis of terrestrial laser scanning and forest growth simulations to determine selected characteristics of Douglas-Fir stands.

Among others, the dbh, basal area, and tree height are the most important parameters to describe tree dimensions in forest inventories. In traditional forest inventories, these parameters are measured manually. In times of forest staff reduction and amalgamation of forest districts, terrestrial laser scanning (TLS) could evolve as a fast, efficient and automatic tool for the determination of basic inventory parameters such as the number of trees, diameter at breast height (dbh), basal area, tree height as well as stem and crown shape parameters. Since there has so far been little attention drawn to the accuracy and precision of TLS itself, we statistically investigated TLS in comparison with traditional inventory methods. We developed an investigation procedure, exemplified for a 49-year-old Douglas-Fir stand (Pseudotsuga menziesii var. Viridis Mirb.) near Eberswalde in the northeastern part of Germany to analyse the potential of TLS in terms of diameter at breast height (dbh) and height measurements. The results of the study suggest that the precision of the dbh measured from the laser scan point cloud return is sufficient. However, TLS was linked to an underestimation of dbh in comparison to the reference values measured with a diameter tape. Stand volume was accurately measured only if multiple scan positions were distributed in the forest stand.

Dynamic Modeling of Soft Magnetic Film Actuated Scanners

Dynamic behavior of magnetic thin film actuators is investigated in detail and applied to various laser scanning applications. Magnetic hysteresis effects are incorporated into the model developed in the prior work, which assumes linear magnetization as a function of magnetic field and is based on the distributed point-by-point calculation of the magnetostatic moments and forces across the film surface. A simple functional form is used to model the major B-H loop of ferromagnetic films. The model is validated with permalloy (Ni-Fe) plated polymer actuators. The actuators are excited using an external electro-coil and the structures deflect due to magnetic anisotropy torque. The ac deflection of the actuators is modeled by calculating the point-by-point moments on the magnetic film and the solution can handle nonuniform external field and unsaturated magnetic film cases. A 25deg optical scan angle is demonstrated for laser scanning display and imaging applications with a nonoptimum coil. Scaling the model to MEMS devices is also discussed.

Terrestrial Laser Scanning of grain roughness in a gravel-bed river

This paper demonstrates the application of Terrestrial Laser Scanning (TLS) to determine the full population of grain roughness in gravel-bed rivers. The technique has the potential to completely replace the need for complex, time-consuming manual sampling methods. Using TLS, a total of 3.8 million data points (mean spacing 0.01 m) were retrieved from a gravel bar surface at Lambley on the River South Tyne, UK. Grain roughness was extracted through determination of twice the local standard deviation (2 σ z ) of all the elevations in a 0.15 m radius moving window over the data cloud. 2 σ z values were then designated to each node on a 5 cm regular grid, allowing fine resolution DEMs to be produced, where the elevation is equivalent to the grain roughness height. Comparisons are made between TLS-derived grain roughness and grid-by-number sampling for eight 2 m 2 patches on the bar surface. Strong relationships exist between percentiles from the population of 2 σ z heights with measured a-, b-, and c-axes, with the closest matches appearing for the c-axis. Although strong relationships exist between TLS-derived grain roughness (2 σ z ), variations in the degree of burial, packing and imbrication, results in very different slope and intercept exponents. This highlights that conventional roughness measurement using gravel axis length should be used with caution as measured axes do not necessarily represent the actual extent to which the grain protrudes into the flow. The sampling error inherent in conventional sampling is also highlighted through undertaking Monte Carlo simulation on a population of 2000 clasts measured using the grid-by-number method and comparing this with the TLS-derived population of grain roughness heights. Underestimates of up to − 23% and overestimates of up to + 50% were found to occur when considering the D 84, and − 20% and overestimates of up to + 36% were found to occur when considering the D 50.

Close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts

This paper reviews the application of close-range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts. Terrestrial remote sensing techniques are being increasingly used as a complement to traditional scanline and window mapping methods. They provide more comprehensive information on rock cuts, allow surveying of inaccessible outcrops, and increase user safety. Selected case studies are used to estimate the accuracy of several 3D model registration approaches and the most time-, effort- and cost-effective methods are highlighted. It is shown that simple registration networks are able to provide adequate measurement of discontinuity orientation for engineering purposes. The case studies presented also illustrate the effects of sampling bias and limitations related to discontinuity characterization using remote sensing techniques. Vertical orientation bias and occlusion can be of particular concern when persistent discontinuities dip at the same angle as the camera/scanner line-of-sight. Major advantages of the techniques are presented illustrating how terrestrial remote sensing techniques provide rapid spatial measurements of discontinuity location, orientation and curvature and are well suited to the quantification of persistence magnitudes greater than 3 m.

Quantifying discontinuity orientation and persistence on high mountain rock slopes and large landslides using terrestrial remote sensing techniques

Abstract. This paper describes experience gained in the application of terrestrial digital photogrammetry and terrestrial laser scanning for the characterization of the structure of high mountain rock slopes and large landslides. A methodology allowing the creation and registration of 3-D models with limited access to high mountain rock slopes is developed and its accuracy verified. The importance of occlusion, ground resolution, scale and reflectivity are discussed. Special emphasis is given to the concept of observation scale and resulting scale bias and its influence on discontinuity characterization. The step-path geometry of persistent composite surfaces and its role in remote sensing measurements are described. An example of combined terrestrial digital photogrammetry and terrestrial laser scanning applied in the generation of a 3-D model of the South Peak of Turtle Mountain, the location of the Frank Slide, is presented. The advantages gained from the combined use of these techniques and the potential offered through long-range terrestrial digital photogrammetry, using high focal length lenses up to 400 mm is illustrated. Special emphasis is given to the potential of this specific technique, which has to the authors knowledge rarely been documented in the geotechnical literature.

High speed laser scanning using MEMS driven in-plane vibratory grating: Design, modeling and fabrication

In this paper, we report a design, modeling and fabrication of a microelectromechanical system (MEMS) based in-plane vibratory sub-wavelength diffraction grating scanner for high optical efficiency, high speed laser scanning applications. This paper demonstrates that with careful design, optical efficiency of more than 75% is experimentally achievable with a simple gold-coated binary sub-wavelength grating. High frequency scanning of 55.01 kHz with an optical scan angle of 5.2° is achievable even when operated in air. The device demonstrated has a 1 mm diameter grating. Through consideration of the mass of the suspension springs, stress alleviation beams and fabrication imperfections, a theoretical model is proposed which can estimate the dynamic performance close to the actual operating condition.

Potential of terrestrial laserscanning in load test measurements of bridges

The state-of-the-art geodetic and remote sensing techniques can prove their potential through particular engineering applications. Besides the traditional surveying terrestrial laserscanning broadens its application field in civil engineering projects. The Department of Photogrammetry and Geoinformatics has long experience in the measurement methods, accuracy analysis and applications of terrestrial laserscanning. This paper deals with the potential of the technology through the examples of load test measurements of Danube bridges. Prior to the particular bridge surveying projects accuracy analysis has been carried out in laboratory measurements, the results validated the accuracy and reliability of the laserscanned data. The paper discusses the complex measurement procedure, the main steps of the data processing and results. Remote sensing can provide data about specific (e.g. with limited accessibility) areas of the structure that cannot be measured with traditional techniques during the short period of the load test measurements. The post-processing includes comparison analysis using ground-based geodetic measurements (such as high precision leveling) as reference in defining displacements. By computing the accuracy measures of the terrestrial laserscanning the overall technology can be qualified and calibrated.

Three-dimensional (3D) visualisation: the application of terrestrial laser scanning in the investigation of historical Scottish farming townships

Recent developments in digital technologies are heralding significant changes in the way we acquire, visualise and analyse archaeological data. Terrestrial laser scanners can be used to create photo-realistic virtual copies of landscapes, and archaeological features, and offer the potential to improve our understanding of three-dimensional (3D) spatial relationships at study sites. Here we present a methodology for the integration of a high-resolution 3D site model with soil chemical data obtained from an abandoned settlement site located in the Central Highlands of Scotland. At this site, the multi-element concentration in soil, co-visualised within a topographic setting, has an important role to play in elucidating settlement layout and activity. The methods described here are also of significance in archiving sites of archaeological/historical importance where development activities and/or environmental processes may destroy remains, or where access to field sites is restricted.

Application of Dynamic Masking on Rapid Prototyping

In rapid prototyping (RP) technologies, curing of UV-curable photopolymers is mainly achieved by the application of laser scanning with limited fabrication speed. The dynamic masking approach can improve the fabrication speed; however, current researches and available systems cure photopolymers with visible light rather than UV light. In this research, we have attempted to develop a UV dynamic masking RP system by implementing digital micro-mirror device (DMD) from digital light processing (DLP) technology and TFT liquid crystal display (LCD) panel. A DLP projector was disassembled and the main components were then recombined to form a dynamic mask generator. Thus, this study has shown the feasibility of obtaining a UV dynamic masking RP system that may be integrated for a UV-curable material processing.

Assessing the applicability of terrestrial laser scanning for spatial snow depth measurements

Abstract Snow depth observation in potentially dangerous avalanche-starting zones is important for avalanche prediction and dimensioning of permanent protection measures. The possible danger of avalanches complicates measurements of snow depth in the field (e.g. by probing). Therefore, the applicability of terrestrial laser scanning to measure the depth of the snow cover was analysed. Different long-range laser profile measuring systems were used carrying out numerous field campaigns (Vorarlberg, Austrian Alps). The objective of the study was to discover under which meteorological and snowpack conditions the measurements must be taken in order to provide accurate results ( 1 mm) only 50% of the emitted signal was received, depending on the angle of incidence. In any case, the accuracy decreases with increasing distance to the target. For distances to the object of more than about 500 m, the accuracy that can be achieved with the used TLS measuring systems is rather low and the errors can be significantly larger than 10 cm.

High-speed, high-optical-efficiency laser scanning using a MEMS-based in-plane vibratory sub-wavelength diffraction grating

In this paper, we report the modeling, fabrication and characterization of a microelectromechanical systems (MEMS)-based sub-wavelength diffraction grating under in-plane motion for high-optical-efficiency high-speed laser-scanning applications. The scanner utilizes in-plane rotational vibration of a planar microstructure to change the orientation of the diffraction grating, hence causing a diffracted laser beam to scan with less dynamic wavefront deformation as compared with conventional scanning micromirrors. An optical efficiency of more than 75% is experimentally achieved with a simple gold-coated binary sub-wavelength grating. When operated in air and electrostatically driven by 45 V dc bias and 84 V peak-to-peak ac voltages, the 1 mm diameter grating is capable of scanning an optical scan angle of 13.7° with a 632.8 nm wavelength incident laser beam at a resonant frequency of 20.35 kHz. The measured optical resolution is around 310 pixels per unidirectional scan.

Application of Three-Dimensional Laser Scanning and Surveying in Geological Investigation of High Rock Slope

The appearance of 3D laser scanning technology is one of the most important technology revolutions in surveying and mapping field. It can be widely used in many interrelated fields, such as engineering constructions and 3D measurements, owing to its prominent characteristics of the high efficiency and high precision. At present its application is still in the initial state, and it is quite rarely used in China, especially in geotechnical engineering and geological engineering fields. Starting with a general introduction of 3D laser scanning technology, this article studies how to apply the technology to high rock slope investigations. By way of a case study, principles and methods of quick slope documentation and occurrence measurement of discontinuities are discussed and analyzed. Analysis results show that the application of 3D laser scanning technology to geotechnical and geological engineering has a great prospect and value.

Innovative applications of laser scanning and rapid prototype printing to rock breakdown experiments

AbstractWe present the novel application of two technologies for use in rock breakdown experiments, i.e. close‐range, ground‐based 3D triangulation scanning and rapid prototype printing. These techniques aid analyses of form–process interactions across the range of scales relevant to breakdown (µm‐m). This is achieved through (a) the creation of DEMs (which permit quantitative description and aanalysis of rock surface morphology and morphological change) and (b) the production of more realistically‐shaped experimental blocks. We illustrate the use of these techniques, alongside appropriate data analysis routines, in experiments designed to investigate the persistence of fluvially‐derived features in the face of subsequent wind abrasion and weathering. These techniques have a range of potential applications in experimental field and lab‐based geomorphic studies beyond those specifically outlined here. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Application of Terrestrial Laser Scanning in determining the pattern of late Pleistocene and Holocene fault displacement from the offset of pluvial lake shorelines in the Alvord extensional basin, northern Great Basin, USA

The northwardtrending Alvord extensional basin of southeastern Oregon lies along the northern margin of the Great Basin. The basin is nearly 200 km long and 15 km wide and is bound and internally dissected by a complex system of active normal faults. The faults cut Pleistocene wave-cut terraces that formed along successive shorelines of pluvial Lake Alvord. The wave-cut terraces are incised into late Tertiary volcanic and sedimentary rocks and unconsolidated Quaternary sediments. The terraces formed during stillstands of the ancient lake, during at least two cycles of lake fill and desiccation in the Pleistocene. Wave-cut terraces are divided into two sets, with the topographically higher and older Serrano terrace series consisting of three shorelines and the Alvord terrace series composed of the five topographically lower and younger shorelines. Shorelines are dated locally, and together with regional correlation to other pluvial lakes, the Serrano highstand is estimated as 200–130 ka and the Alvord highstand as 20–15 ka. High-resolution topographic images of the terrace morphology acquired by Terrestrial Laser Scanning georeferenced with the Global Positioning System allowed detailed analysis of shoreline altitudes where they are crosscut by faults. Variation in shoreline altitude measured across faults and on opposing sides of the basin indicates that fault slip occurred during and following periods of lake-level recession. The Serrano terrace highstand records a cumulative vertical displacement of 137.5 ± 3.6 m and the vertical offset of the younger Alvord terrace series highstand is 72.5 ± 2.8 m. Fault displacement is heterogeneously distributed across the basin. Faults along the western margin of the basin accommodated nearly 50% of the total displacement, with one fault accommodating over 20% of the total displacement budget. The residual displacement is distributed across the basin. As much as 30% of the cumulative offset is taken up by structures concealed beneath basin cover and 20% by structures exposed in the highlands along the eastern flank of the basin. Since formation of the Alvord shorelines, the rate of fault displacement was nonperiodic and the basin underwent elevated activity in the late Pleistocene and early Holocene. Vertical displacement rates vary through time, and offset of Alvord terraces occurred at 3.6–7.3 mm/yr, whereas displacement of the Serrano terraces ranged from 0.7 to 1.1 mm/yr. When the horizontal component of motion is calculated by using fault dips of 60°, the 104 yr time-scale rate determined from the Alvord terraces is as much as 2.4–4.2 mm/yr and exceeds the contemporary horizontal displacement across the basin of 1.75 mm/yr determined geodetically. The 105 yr horizontal displacement rate calculated for the Serrano highstand is substantially lower, 0.4–0.6 mm/yr. Spatial and temporal pattern of faulting within the Alvord basin illustrates the complexity of strain release within the basin and highlights the length- and time-scale dependence of deformation rate estimation within extensional basins.

On-the-job detection and correction of systematic cyclic distance measurement errors of terrestrial laser scanners

Application of terrestrial laser scanning for engineering and documentation projects requiring high accuracy is often prohibitive due to the error budget of terrestrial laser scanners (TLS) which is worse than that of alternative instruments such as total stations. However, by separating the errors of TLS into random and systematic components, the influence of both can be reduced significantly. Approaches for reducing the influence of random noise rely on averaging. One method is introduced briefly as it is relevant for the task of the proposed systematic error removal. We discuss the correction of cyclic distance measurement errors of TLS in detail. For the investigated scanner, these cyclic errors are the most dominant systematic errors. The proposed approach is based on an on-the-job determination of a distance correction function which allows reducing the magnitude of the occurring distance errors by a factor of ten, reducing the systematic errors to less than 0.5 mm. The massive amount of data acquired by TLS is exploited using robust statistical methods. The algorithm developed relies on small, flat surfaces found automatically in the scene. Hence, the method can be applied on engineering project data without requiring additional laboratory experiments. Therefore, it is not essential that the errors are constant over time. By the introduction of on-the-job correction procedures as the one proposed, the systematic errors of TLS can be decreased significantly. This makes them more suitable to be used as an alternative to single point measurement devices.

激光共聚焦显微镜在磨损表面粗糙度表征中的应用

激光共聚焦显微镜在磨损表面粗糙度表征中的应用

3D Laser Scanning in Digitization of Current Production Systems

The paper presents the results of research realised in 3D laser scanning and digitization of large size objects of the current production systems. The developed and validated methodology shows the procedure of 3D laser scanning application by the digitization of production halls, machine tools, equipment, etc. The described procedure was tested and validated in chosen industrial companies. The paper also presents achieved benefits and future research goals.

Application of laser scanning for developing a 3D digital model of an open-pit side surface

A method is described for the 3D survey of an open-pit side surface by using a laser scanner in order to develop a 3D digital model for identification of the hierarchical structure of geoblocks at a limestone deposit. The main principles of the laser scanning are explained, recommendations are given for the selection of the scan stations arrangement to survey a vertical open-pit side. The computer-aided scanning-data processing technique is presented for the graphical-analytical representation and system analysis of the experimental geomechanical information on the real rock mass.