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A 3D laser scanning strategy based on cascaded deep neural network is proposed for the scanning system converted from 2D Lidar with a pitching motion device. The strategy is aimed at moving target detection and monitoring. Combining the device characteristics, the strategy first proposes a cascaded deep neural network, which inputs 2D point cloud, color image and pitching angle. The outputs are target distance and speed classification. And the cross-entropy loss function of network is modified by using focal loss and uniform distribution to improve the recognition accuracy. Then a pitching range and speed model are proposed to determine pitching motion parameters. Finally, the adaptive scanning is realized by integral separate speed PID. The experimental results show that the accuracies of the improved network target detection box, distance and speed classification are 90.17%, 96.87% and 96.97%, respectively. The average speed error of the improved PID is 0.4239°/s, and the average strategy execution time is 0.1521 s. The range and speed model can effectively reduce the collection of useless information and the deformation of the target point cloud. Conclusively, the experimental of overall scanning strategy show that it can improve target point cloud integrity and density while ensuring the capture of target.

Fabrication of thin-wall components using the laser powder bed fusion (LPBF) additive manufacturing (AM) technology was investigated for two “hard-to-weld” high gamma prime Ni-based superalloys RENE 65 (R65) and RENE 108 (R108). Simple block parts with wall thicknesses of 0.25 mm, 1.00 mm, and 5.00 mm are printed using a bidirectional laser scanning strategy without layer-wise rotation. Parts with walls thinner than 5 mm fail before reaching the designated build height. Results indicate that reduction of limiting build height (LBH) corresponds to the reduction of part thickness and is unaffected by alloy composition. On the contrary, the number of internal micro-cracks along columnar grain boundaries in the build direction (BD) increases with part thickness and is significantly higher in R108 than R65. These findings suggest that reduced LBH in parts with thinner walls is not caused by internal micro-crack formation. Fractography and finite element analysis (FEA) of the in-process thermal stresses show that the LBH trend is not explained by the conventional cracking mechanism. Simulations suggest that part thickness affects stress distribution leading to more substantial distortion and consequent failure to add layers for continued fabrication of thinner parts.

To improve the quality of narrow overlap welds and reduce cost during the high-strength production, it is essential to detect weld defects promptly by identification of the type of defects to provide solution accordingly. This paper proposes an integrated weld defect identification approach combing eddy current detection with 3D laser scanning based on Convolutional Neural Networks (CNN). The detection principle and equipment of the two detection methods are introduced. To fit the training process of CNN, two set of detection signals are preprocessed: a two-dimensional time-frequency diagram for eddy current signals using continuous wavelet transform and for laser images, weld edges are extracted and divided by region using image convolution and combining with integral graph. CNN model VGG16 is trained afterwards with data collected from one local manufacturer in Shanghai. It is discovered that performance of eddy current and laser image identification on different types of weld defects is different, and the accuracy can be increased with the two methods combined. Last, to achieve real-time detection of narrow overlap welding, a two-stage defect recognition model is built which greatly improves the efficiency of weld defect identification without affecting the accuracy of weld defect identification.

Multi-sensor data fusion has recently gained a wide attention within the Geomatics research community, as it helps overcome the limitations of a single sensor and enables a complete 3D model for the structure and a better object classification. This study develops a data fusion algorithm, which optimally combines sensor data from a terrestrial and an unmanned aerial system (UAS) to obtain an improved and a complete 3D mapping model of a structure. Terrestrial laser scanner (TLS) data are collected for the exterior of a building along with the DJI Phantom 4 Pro and terrestrial close-range Sony α7R camera images. A number of ground control points and targets are established throughout the scanned building for the photogrammetric process and scans registration. Different point cloud datasets are generated from the TLS, UAS and the terrestrial Sony camera images. The created point clouds from each individual sensor and the fused point clouds are used in different forms, namely the original, denoised and subsampled point clouds. The denoised point cloud dataset is generated through the application of the statistical outlier remover (SOR) filter on the original point clouds. The relative precision of the 3D models is investigated using the multiscale model-to-model cloud comparison (M3C2) method. The TLS-based 3D model is used as a reference. It is found that the precision of the Sony-based 3D model is higher than the other two models for the original and denoised datasets. The fused Sony/UAS-based model provides a complete 3D model with precision higher than the UAS-based model.

Visibility is a key factor influencing animal behavior in forest ecosystems. Fine-scale visibility in forested areas has been measured by ground-based approaches at the plot level, using site-specific methods that have limited spatial coverage. Here we examine airborne laser scanning (ALS) as a novel tool to quantify fine-scale visibility in the temperate forests of Germany at a landscape scale. We validate the (vertically-derived) ALS-derived visibility measures using proven (horizontally-derived) terrestrial laser scanning (TLS) estimates of true visibility. Our results indicate that there is a good agreement between the visibility resulting from ALS and TLS with an R2 ranging from 0.53 to 0.84 and a normalized RMSE varying from 15.92% to 11.81% at various plot sizes, with the highest accuracy achieved using a plot size of 35 × 35 m. Our study demonstrates for the first time that ALS can be successfully applied to quantify fine-scale visibility in temperate forests at a landscape level. This approach holds potential for studying the spatial behavior of animals (e.g., habitat selection and predator–prey relationships) in forest ecosystems.

This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing demands for high surface quality in metal additive manufacturing. The proposed synchronized control system is composed of a motion decomposition module and an error synthesis module. The experimental results show that stitching errors can be avoided thanks to continuous motion during laser processing. Moreover, in comparison with the existing step-scan method, the processing efficiency of the proposed method is improved by 38.22% and the surface quality of the laser-polished area is significantly enhanced due to a more homogeneous distribution of the laser energy during the material phase change. The proposed synchronized system paves the way for high-speed, high-precision, and large-area laser material processing without stitching errors.

Modelling of bridge structures is an important topic due to the increasing need to get accurate information in a visual way. Registration between as-built laser data and global design reference one is necessary to guarantee the validity and dependency of the proposed model. This research presents a new registration method based on artificial neural networks (ANN) methodology. A developed software is implemented to apply ANN and to achieve the research objective. A steel structure bridge is chosen for the application of the proposed system. A point cloud laser data (as built) of the bridge is registered to the design model. The results show that the developed registration method is potential and reliable due to the insignificance of the error between both as-built model and the design model. The assumed level of significance is 95% and the error between as-built model and the design model after the registration process is found to be less than 5%. So, one concludes that the developed method can be used as a registration method for the laser scanning bridge structures. Some recommendations are presented to the future study concerned with using deep learning (DL) to apply the registration process to get better results.

In this paper, a novel approach was proposed to achieve the joining of AlN and Cu by nanosecond laser pre-irradiation of AlN. The effects of the speed of laser scanning on the morphology, chemical compositions, and properties of the surface of AlN ceramic and the mechanism of laser-assisted joining of AlN and Cu were investigated. With the increase of the speed of laser scanning, the surface roughness of AlN decreased. After nanosecond laser irradiation, element Al was detected on the surface of AlN. When nanosecond laser irradiation was applied, the hydrophilicity and the surface energy of the ceramic surface were improved. The modified AlN was successfully joined to Cu at the temperature of 620 °C with a speed of laser scanning of 500 or 1000 mm/s. The results of TEM confirmed the presence of Al4Cu9, indicating the metallurgical combination of Cu and AlN. Also, the method presented in this paper was supposed to be of great reference significance for the joining of ceramics and metals.

The airborne light detection and ranging (LiDAR) bathymetry (ALB) system is an extension of the ubiquitous topographic LiDAR mapping system and has been most simply characterized as adding a green laser to the infrared laser of topo systems. Due to the low point cloud density and monotonous objects in the scene, it is difficult to mosaicing the ALB strips. Therefore, the existing airborne laser scanning strip stitching algorithm has poor performance for ALB strips. In this article, a coarse-to-fine strip mosaicing model for ALB is proposed. The framework is fast and efficient and can handle large ALB data. An improved alpha shapes algorithm can fast and accurately determine the overlap region of strip is applied. Due to different data accuracy and spatial characteristics, the water area and land area are processed separately. A weight distribution-based coarse-to-fine registration model is designed for underwater areas. The topological constraint term is added to the nonrigid iterative closest point (ICP) cost function to prevent excessive deformation caused by outliers. The implicit B-spline surface fitting algorithm using the 3L algorithm and the least-squares trend surface fitting algorithm are applied separately to assign weights for overlapping strips to solve the limitation of no control or less control. Moreover, a random sample consensus (RANSAC)-ICP registration model characterized by the normal vector and curvature is constructed for land area. Finally, the comparisons with ICP highlight the superiority of the proposed approach in flexibility and accuracy. The root-mean-square error (RMSE) is 0.12 m and the maximum error is 0.36 m.

We introduce an autonomous laser kirigami technique, a novel custom manufacturing machine system which functions somewhat similar to a photocopier. This technique is capable of creating functional freeform shell structures using cutting and folding (kirigami) operations on sheet precursors. Conventional laser kirigami techniques are operated manually and rely heavily on precise calibrations. However, it is unrealistic to design and plan out the process (open loop) to realize arbitrary geometric features from a wide variety of materials. In our work, we develop and demonstrate a completely autonomous system, which is composed of a laser system, a 4-axis robotic arm, a real-time vision-based surface deformation monitoring system, and an associated control system. The laser system is based on the Lasersaur, which is a 120-Watt CO2 open source laser cutter. The robotic arm is employed to precisely adjust the distance between a workpiece and the laser lens so that a focused and defocused laser beam can be used to cut and fold the workpiece respectively. The four-axis robotic arm provides flexibility for expanding the limits of possible shapes, compared to conventional laser machine setups where the workpiece is fixed on rigid holders. The real-time vision-based surface deformation monitoring system is composed of four low-cost cameras, an integrated AI-assisted algorithm, and the sensors (detachable planar markers) mounted on the polymer-based sheet precursors, and allows real-time monitoring of the sheet forming process and geometric evolution with a geometric feature estimation error less than 5 % and delay time around 100ms. The developed control system manages the laser power, the laser scanning speed, the motion of the robotic arm based on the designed plan as well as the close-loop feedback provided by the vision-based surface deformation monitoring system. This cyber-physical kirigami platform can operate a sequence of cutting and folding processes in order to create kirigami objects. Hence, complicated kirigami design products with various different polygonal structures can be realized by undergoing sequential designed laser cuts, and bends (at any folding angles within designed geometric tolerance) using this autonomous kirigami platform.

The analysis of topographic time series is often based on bitemporal change detection and quantification. For 3D point clouds, acquired using laser scanning or photogrammetry, random and systematic noise has to be separated from the signal of surface change by determining the minimum detectable change. To analyse geomorphic change in point cloud data, the multiscale model-to-model cloud comparison (M3C2) approach is commonly applied, which provides a statistical significance test. This test assumes planar surfaces and a uniform registration error. For natural surfaces, the planarity assumption does not necessarily apply, in which cases the value of minimal detectable change (Level of Detection) is overestimated. To overcome these limitations, we quantify an uncertainty information for each 3D point by propagating the uncertainty of the measurements themselves and of the alignment uncertainty to the 3D points. This allows the calculation of 3D covariance information for the point cloud, which we use in an extended statistical test for equality of multivariate means. Our method, called M3C2-EP, gives a less biased estimate of the Level of Detection, allowing a more appropriate significance threshold in typical cases. We verify our method in two simulated scenarios, and apply it to a time series of terrestrial laser scans of a rock glacier at two different timespans of three weeks and one year. Over the three-week period, we detect significant change at 12.5% fewer 3D locations, while quantifying additional 25.2% of change volume, when compared to the reference method of M3C2. Compared with manual assessment, M3C2-EP achieves a specificity of 0.97, where M3C2 reaches 0.86 for the one-year timespan, while sensitivity drops from 0.72 for M3C2 to 0.60 for M3C2-EP. Lower Levels of Detection enable the analysis of high-frequency monitoring data, where usually less change has occurred between successive scans, and where change is small compared to local roughness. Our method further allows the combination of data from multiple scan positions or data sources with different levels of uncertainty. The combination using error propagation ensures that every dataset is used to its full potential.

A single-step reduction and patterning technique that involves high-pulse nanosecond fiber laser irradiation was used to reduce graphene oxide films (GOFs) for use in ceramic-based heaters. Laser reduction of GOFs was performed at a laser power, scan speed, pulse repetition frequency, and laser scan pitch of 2.2–4.1 W, 150–500 mm/s, 750 kHz, and 10 μm, respectively. The optimal intensity ratios of the D to G band (RD/G) and the 2D to G band (R2D/G) of reduced GOFs (RGOFs), obtained from Raman spectra, were 0.251 and 0.587, respectively. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that oxygen-containing functional groups in RGOFs coated onto ceramic substrates were removed by increasing the average laser power and decreasing the laser scanning speed. Moreover, the typical RGOFs exhibited a lowest sheet resistance of 22.75 ± 2.75 Ω/□, which was achieved with an average laser power and scan speed of 3.35 W and 300 mm/s, respectively. The highest temperature of the typical laser-patterned RGOFs was approximately 123.3 °C, which occurred when the RGOFs were produced using a laser power, scan speed, and applied direct current voltage of 3.27 W, 200 mm/s, and 10 V, respectively.

In contrast to topographic laser scanning, laser hydrography must take into account the presence of two media. A pulsed laser beam, which enters the water from the air at an oblique angle, is refracted at the air–water boundary in the direction of the plumb line. This change in the direction described by Snellius’ law is caused by a slower speed of the light wave in the water, i.e., the phase velocity. Light scattering caused by turbidity gives rise to further deviations from the straight path. Together, the slower speed and the turbidity-induced path extension cause a longer pulse round trip time in the water than in the air. For an accurate measurement, it is important to correct this propagation time extension. It is a common practice to assume the phase velocity as the velocity for the laser pulses in water. In a dispersive medium, however, the phase velocity is only an approximation of the velocity of a pulse. In media with chromatic dispersion, the pulses propagate with a different velocity, i.e., the group velocity. In water, using the group velocity instead of the phase velocity reduces the range dependent bias of the depth measurement at a laser wavelength of 532 nm by more than 1.5%. We present an easy to perform an experiment, which shows that the group velocity differs so much from the phase velocity that this difference should be taken into account. We further discuss the use of group velocity to explain the depth bias using examples from the literature.

The aim of the paper is to present some experiences of using modern technologies to historical buildings digitalization. The emphasis is placed on the possibilities of spatial data collecting, as well as on subsequent 3D modelling. The paper describes the proposed survey techniques which are based on the Terrestrial Laser Scanning and photogrammetry. The authors obtained the point cloud by using the laser scanner Faro Focus 3D and dedicated software to combine scans (target based and cloud to cloud methods). The paper also provides an introduction to issues related to a method of building structure modelling based on a pointcloud. The authors proposed some computer software tools that could improve work with a point cloud and the modelling process. The resulting 3D model could be both a source of information about historical building and a sufficient base to create computational model with spatial finite elements. The subject of the case study is the St. Hubert Chapel located in Rzeszów (Poland) and built in the middle of the 18th century under the patronage of the Lubomirski family. This rococo chapel is one of the most valuable architectural monuments in the region. Historical Building Information Model (HBIM) could be helpful in analysis, visualisations and conservation practice of this precious monument. Diagnosing the current object state and assessing its technical condition could be the purpose of creating a computational FEM model.

Laser Powder-Bed Fusions (LPBF), a class of additive manufacturing (AM), is a promising technique for producing components with complex geometry design. However, parts fabricated by LPBF suffer from residual stresses arising due to substantial temperature gradients inherent to the process. Numerical models are unable to provide a comprehensive thermal history of the built materials efficiently due to the mismatch between the characteristic length scales and infinitesimal time steps needed for complete simulations. In the present work, an extended Rosenthal’s model is presented by considering the effects of various heat dissipation/consumption mechanisms. The modeling results of energy auditing of thermal boundary conditions for stainless steel (SS17-4PH) laser melting indicated that the total energy losses by convection, radiation, and melting are less than 20% among which, radiation is the most dominant part. A comparison of the results obtained by the extended Rosenthal’s equation with finite element numerical predictions and experimental data shows a good agreement. Also, a parametric study has been conducted to identify the influence of laser scanning velocity, beam radius, and power on the overall temperature distributions and melt geometry. The present study can pave the way for the prospective use of this methodology to conduct further investigation such as microstructure analysis and thermo-mechanical modeling which are needed to predict residual stresses and distortions.

In industrial manufacturing of bright steel rods, one important quality factor is the straightness or straightness deviation. Depending on the application, deviations of less than 0.1 mm per meter rod length are desired and can be reached with state-of-the-art manufacturing equipment. Such high-quality requirements can only be guaranteed with continuous quality control. Manual straightness measurements conducted offline using a dial gauge provide accurate results on single positions of the rod. We propose a contactless, optical measurement technique based on laser scanning which has the potential to be used inline during production to inspect all rods over the entire length. Only for calibration of the system the rod needs to be turned around its axis. For the measurement of straightness deviation, it is not required to turn the rod. The method is based on evaluating the intensity signal of the reflected laser radiation against the scan angle. It is shown that in combination with an accurate calibration, this signal can be used to determine the rod’s deviation from a straight rod. We explain the measurement and calibration principle as well as data evaluation. We present the experimental setup and first measurement results on a single position on several samples. For a homogeneous sample surface and neglecting laser drift, accuracy and precision were determined to be in the range of 10–20 μm. We discuss the working principle of a potential inline system.

With the developing technologies, the use of unmanned aerial vehicles’s (UAV) is increasing in all areas. Compared with the conventional photogrammetry and remote sensing sensors, UAVs are more convenient to collect data for small areas. In this study, the accuracy of UAV products was investigated in the archeological area of Eskişehir Şarhöyük. In order to produce reference data for the orthophoto and DTM accuracy analysis, a digital map from the test area was produced using in-situ measurements. Also, for the comparison of the point cloud, a small test area was determined and reference point cloud data was collected with terrestrial laser scanner. The comparison of the results showed significant difference between the UAV images and images collected by conventional methods. Thus, while there was 1 m difference between the data without the use of control points, and the use of control points significantly improved the results.

Airborne laser scanning (ALS) has emerged as a technology capable of generating descriptors of vegetation structure and best available terrain information. Research and operational implementations of ALS data have highlighted their value for characterizing forest structure and generating spatially explicit and objective spatial coverages and mapping products for forest management. Continued emphasis to enhance forest stewardship is promoting novel methods to integrate ALS to detail non-timber ecosystem values like habitat, soil, and water. Standardized criteria and indicator frameworks such as the Canadian Council of Forest Ministers provide a reliable starting point for where ALS has opportunities to characterize ecosystems objectively regardless of location. In this review of primarily Canadian work, we highlight how ALS is becoming an increasingly viable technology for deriving meaningful indicators to meet sustainable forest management criteria. We review and highlight the value of ALS for quantifying indicators of biological diversity, ecosystem condition and productivity, soil and water, and the role of forests in global ecological cycles. We conclude by highlighting the need for increased education, tech transfer, flexible software, and reporting frameworks alongside five key considerations for using ALS to derive meaningful indicators of sustainable forest management.

Laser cladding with SiC nanoparticles was performed on a Ti-6Al-4V substrate in an air environment. In this process, the oxide and reinforcement phases formed together in the coating layer and, consequently, the hardness and friction characteristics of the titanium surface were improved simultaneously. Specifically, the oxide phases such as SiO2 and TiO2 were formed on the top region of the coating layer through a reaction with oxygen. The reinforcement phases such as TiC and Ti5Si3, a eutectic structure, and martensite occurred in the lower region of the coating below the oxide phases. The reinforcement phases helped increase the hardness of the titanium surface by up to three times. Moreover, due to the influence of the oxide phases, the friction coefficient was reduced by up to 88% after the laser cladding. When the laser scanning speed decreased, the cooling rate decreased; therefore, the crystal size increased, and hardness value decreased. In addition, the friction coefficient decreased as the laser scanning speed decreased due to the increase in the TiO2 content and decrease in the agglomerated SiO2 at low laser scanning speeds. The amount of wear of the specimen reduced considerably after the laser cladding, and only light abrasive wear and fatigue wear were observed on the laser clad surface.

This research focuses on specimen geometry and the associated surface roughness of H13 hot-work tool steel, processed using laser-directed energy deposition additive manufacturing, and varying both the powder feed rate and the laser scanning speed. Under the examined conditions, the test sample measurements of length and width did not vary, but the sample heights were significantly affected by the scanning speed. An increase in scan speed resulted in ‘underbuilding’, while a decrease resulted in ‘overbuilding’, as might be anticipated. The top surface roughness of the samples was found to be greater than the side surface roughness, due to the capture of extra powder particles. For the single-track and multitrack clad samples, the surface roughness was increased when decreasing the scan speed. The addition of a draft angle, when producing 3-D components, was shown to reduce the side surface roughness. Using a finer layer thickness results in overbuilding the target height, while a coarser layer thickness results in underbuilding. Finally, the surface roughness exhibited no clear trend when the layer thickness was changed.

Purpose This paper aims to provide a detailed study on influence of the laser energy density on mechanical, surface and dimensional properties of polyamide 12 (PA12) parts produced by selective laser sintering (SLS), providing the microstructural and crystallization evolution of the samples produced at different energy densities. Design/methodology/approach Making use of a space filling design of experiments, a wide range of laser sintering parameters is covered. Surface morphology is assessed by means of profile measurements and scanning electron microscopy (SEM) images. Mechanical testing, SEM, X-ray diffraction (XRD), differential scanning calorimeter (DSC) and infrared spectroscopy (FTIR) were used to assess the influence of energy density on structural and mechanical properties. Findings Results show a high dependency of the properties on the laser energy density and also a compromise existing between laser exposure parameters and desired properties of laser sintered parts. Surface roughness could be associated to overlap degree when using higher scan line spacing values and lower laser speeds improved surface roughness when high scan line spacing is used. Higher mechanical properties were found at higher energy density levels, but excessively high energy density decreased mechanical properties. A transition from brittle to ductile fracture with increasing energy density could be clearly observed by mechanical analysis and SEM. XRD and DSC measurements show a decrease on the crystal fraction with increasing energy densities, which corroborated the plastic behavior observed, and FTIR measurements revealed polymer degradation through chain scission might occur at too high energy densities. Originality/value Valuable guidelines are given regarding energy density optimization for SLS of PA12 considering not only quality criteria but also microstructure characteristics. Surface properties are studied based on the concept of degree of overlap between laser scanning lines. For the first time, crystallization behavior of SLS PA12 parts produced at different energy levels was studied by means of XRD measurements. Polymer degradation of SLS PA12 parts was evaluated with FTIR, which is a non-destructive and easy test to be conducted.

Various means of extracting road boundary from mobile laser scanning data based on vehicle trajectories have been investigated. Independent of positioning and navigation data, this study estimated the scanner ground track from the spatial distribution of the point cloud as an indicator of road location. We defined a typical edge block consisting of multiple continuous upward fluctuating points by abrupt changes in elevation, upward slope, and road horizontal slope. Subsequently, such edge blocks were searched for on both sides of the estimated track. A pseudo-mileage spacing map was constructed to reflect the variation in spacing between the track and edge blocks over distance, within which road boundary points were detected using a simple linear tracking model. Experimental results demonstrate that the ground trajectory of the extracted scanner forms a smooth and continuous string just on the road; this can serve as the basis for defining edge block and road boundary tracking algorithms. The defined edge block has been experimentally verified as highly accurate and strongly noise resistant, while the boundary tracking algorithm is simple, fast, and independent of the road boundary model used. The correct detection rate of the road boundary in two experimental data is more than 99.2%.

Previous research work shows that metal nanocomposite thin films fabricated by laser sintering of mixtures of metal nanoparticles (NPs) and carbon nanotubes (CNTs) on a polymer substrate have a great potential to help enhance reliability and durability of metal components in flexible electronic devices. To gain a good relevant fundamental understanding, it is important to know the material thermal history during laser sintering. However, an in-situ temperature measurement has been rarely reported in a paper in the literature for laser sintering of metal NP-CNT mixture thin films on a polymer substrate. Such temperature measurements are reported in this paper, which are performed using a two-color pyrometry system set up by the authors to overcome related technical challenges such as high spatial and temporal resolution requirements. The measurement method is non-contact, and by measuring thermal radiation in two wavelength ranges it does not require the value of the target surface emissivity. The electrical resistivities of composite material sintered with different laser scanning speeds are also measured. Under the conditions studied, it has been found that as the laser scanning speed increases significantly, the average melted material temperature in the measurement spot only slightly decreases, but the melting duration drops significantly. The average electrical resistivity of sintered composite material first decreases and then increases with the laser scanning speed. The measured material surface temperatures for laser sintering of CNT and silver NP mixtures are similar to those for laser sintering of silver NPs with the same laser scanning speed.

In order to investigate the removal mechanism of C/SiC composites processed by nanosecond laser, and to obtain a groove width and depth with better consistency, in this study, a nanosecond laser was used to ablate 2.5-dimensional C/SiC composites to explore the influence of laser processing parameters and fibre arrangement on the ablation morphology. The experimental results were analysed based on the finite element simulation. The results showed that the amount of material removed and ablation morphology varied considerably between the start and end of the grooves, and the edge effect was pronounced. In addition, the morphology of the ablated groove was affected by the fibre arrangement direction. The temperature field of the C/SiC composite during laser processing was simulated using finite element software. The simulation results intuitively showed that there was a temperature difference between the start and end of the ablation. Further, the temperature field distribution varied by position. Finally, the ablation removal mechanism for the nanosecond laser processing of 2.5-dimensional C/SiC composites was explored by experimental and temperature field simulation results, and laser scanning parameters were optimized to obtain the groove width and depth with better consistency.

Today there is a gap between a presence of various new equipment on the market which provides streams of various digital data about the environment, in particular in the form of laser scanning point clouds, and the lack of adequate efficient methods and software for information extraction from such data. A solution to the problem of bridging this gap is proposed on the basis of neural modeling field theory and dynamic logic (DL). We present a DL-based method of extracting and analyzing information from hybrid point clouds, which include not only spatial coordinates and intensity, but also the color of each point, and can be from multiple sources including terrestrial, mobile and airborne laser scanning data. The proposed method is significant for creating a fundamental theoretical basis for new application algorithms and software for many new applications, including building information modeling, “smart city” environment, etc. The proposed method is fairly new to solving various problems related to extracting semantically rich information from a nontraditional type of digital data, especially hybrid point clouds created from laser scanning. This method will allow to significantly expand the existing boundaries of knowledge in the field of extraction and analysis of information from various digital data, because neural modeling field theory and DL can improve the performance of relevant calculations and close the existing gap in analysis of digital images.

The purpose of this work is to develop a methodology for monitoring real estate objects, as a single information block, by including this procedure for capital construction objects in the process of land use control to update the information contained in state systems. The object of the research is the systems of state monitoring of land use based on the automated information system of state monitoring of land and registration of immovable objects based on the federal state information system of the Unified State Register of Real Estate. The subject of the work is creation a concept for a system of monitoring immovable objects, as a single resource, by introducing a monitoring unit for capital construction ones. As a result of the research, the stages of the method implementation are described, the key users of the final monitoring system for real estate objects are presented and options for its practical application are indicated.

Irradiation of yttria-stabilized zirconia (YSZ) was performed by a femtosecond pulsed laser to investigate the feasibility of V-shaped groove microstructure fabrication. Firstly, fundamental characteristics of microgroove fabrication was investigated by varying scanning speed of laser and number of scans. Higher scanning speed resulted in a smooth surface without any debris adhesion. By increasing number of scans, the cross-sectional profile of the microgroove became a well-defined V shape, and the taper angle of the V-shaped groove can be precisely controlled by laser scanning speed. Moreover, the laser-induced phase transformation of YSZ was characterized, and it was found that the monoclinic ratio after irradiation decreased in comparison with original YSZ surface, indicating improved strength and toughness. TEM cross-sectional observation of the microgrooves was performed and tetragonal phase was detected independent of locations. Finally, micro pyramid structures were created on the YSZ surface by perpendicularly crossing the laser scan directions. The resulting surface showed a drastic change in surface wettability. These findings demonstrated the possibility of generating precise complex microstructures on YSZ surface with high functionality and low subsurface damage, presenting great potential of wide applications in industry.

Studies have shown that melt-pool characteristics such as melt-pool size and shape are highly correlated with the formation of porosity and defects in parts built with the laser powder bed fusion (L-PBF) additive manufacturing (AM) processes. Hence, optimizing process parameters to maintain a constant melt-pool size during the build process could potentially improve the build quality of the final part. This paper considers the optimal control of laser power, while keeping other process parameters fixed, to achieve a constant melt-pool size during the laser scanning of a multi-track build under L-PBF. First, Gaussian process regression (GPR) is applied to model the dynamic evolution of the melt-pool size as a function of laser power and thermal history, which are defined as the input features of the GPR model. Then a constrained finite-horizon optimal control problem is formulated, with a quadratic cost function defined to minimize the difference between the controlled melt-pool size and its reference value. A projected gradient descent algorithm is applied to compute the optimal sequence of laser power in the proposed control problem. The GPR modeling is demonstrated using simulated data sets, a mix of simulated and experimental data sets, or pure experimental data sets. Numerical verification of the control design of laser power is performed on a commercial AM software, Autodesk’s Netfabb Simulation. Simulation results demonstrate the effectiveness of the proposed GPR modeling and model-based optimal control in regulating the melt-pool size during the scanning of multi-tracks using L-PBF.

To ensure unmanned autonomous movement of ground robotic means, it is required to accurately determine the position and orientationof the robot. The present study is related to the estimation of coordinates by comparing the scans of a laser scanning rangefinder in conditionsof semi-structed infrastructure and the absence of a global satellite communications signal. The existing methods of comparing scans havesignificant drawbacks in the conditions of movement over a semi-structured terrain, associated both with the processing time of data fromthe laser scanning rangefinder, and with the quality of the results obtained. The scan is preliminarily placed in a map consisting of cells.Each cell of around point scan is described by forces represented by the laws of physics or probability theory. In the cells of the map, wetake into account the mutual influence of all forces from each point of the scan and thus we obtain the resulting artificial potential field ofthe scan. The position of the robot is estimated by the change in the number of acting forces of one scan per points of the next scan takinginto account their direction. We estimate the orientation of the robot based on the sum of the vector products of the forces and distancesto the given forces acting on the points of the next scan. This method allows you to calculate the displacement of the robot between scansregardless of road conditions and terrain. This article presents the results of an experimental verification of the method on a mock-up of amobile robot equipped with a Velodyne HDL-32 LIDAR. We indicate the operating conditions of the method for a given LIDAR, as wellas the time spent on calculating the bias estimate. Given the peculiarities of the LIDAR, we present a method for eliminating the DopplerEffect (distortion) for the original point cloud. A comparative analysis of the developed method for integrating wheel odometry data, inertialand satellite navigation using the Extended Kalman Filter shows the applicability of this method to assess the position and orientation of therobot in conditions of its movement over rough terrain.

Spontaneous wrinkling of films with a thickness gradient offers a new opportunity for constructing various 3D hierarchical surface morphologies. Unfortunately, accurately and facilely controlling the gradient film thickness to yield multiscale and 3D hierarchical micro-/nanostructures is still difficult. Here, a rapid, facile, and highly controllable fabricating strategy for realizing 3D multiscale hierarchical micro-/nanofolds on a shape memory polymer (SMP) surface is reported. First, the nanoparticle film with gradient thickness is rapidly (100 ms to 4 s) and facilely obtained by laser intermittent ablation on the SMP, termed as laser ablation-induced gradient thickness film. Following one-time constrained heating, the 3D micropillars grow out of the substrate based on the "self-growing effect," and the nanoparticle gradient film on its top shrinks into multiscale micro-/nanofolds simultaneously. Significantly, the evolution process and the underlying mechanism of the 3D micro-/nanofolds are systematically investigated. Fundamental basis enables us to accurately regulate the gradient thickness of nanoparticle films and feature size of folds by varying laser scanning times and scanning path. Finally, desirable patterns on micro-/nanofolds can be readily realized by programmable laser cleaning technology, and the tunable adhesion of the water droplet on the multiscale structured surface is demonstrated, which is promising for microdroplet manipulation.

Recently, three-dimensional (3D) laser scanning technology using terrestrial laser scanner (TLS) has been widely used in the fields of plant manufacturing, civil engineering and construction, and surveying. It is desirable for the operator to be able to immediately and intuitively confirm the scanned point cloud to reduce unscanned regions and acquire scanned point clouds of high quality. Therefore, in this study, we developed a method to superimpose the point cloud on the actual environment to assist environmental 3D laser measurements, allowing the operator to check the scanned point cloud or unscanned regions in real time using the camera image. The method included extracting the correspondences of the camera image and the image generated by point clouds by considering unscanned regions, estimating the camera position and attitude in the point cloud by sampling correspondence points, and superimposing the scanned point cloud and unscanned regions on the camera image. When the proposed method was applied to two types of environments, that is, a boiler room and university office, the estimated camera image had a mean position error of approximately 150 mm and mean attitude error of approximately 1°, while the scanned point cloud and unscanned regions were superimposed on the camera image on a tablet PC at a rate of approximately 1 fps.

In this study, we developed a new system that outputs the additional press work procedures necessary to obtain the desired ship-hull surface. This study is unique in terms of determining the additional press work procedures required according to the current plate shape at any work stage by measuring the plate shape using a laser scanner. In the proposed method, a B-spline surface is constructed from a point cloud measured using a laser scanner, and the current plate shape is analyzed based on differential geometry. Additional press lines are estimated based on the difference in the normal curvature along the lines of curvature between the designed target surface and the current surface. We demonstrated the effectiveness of our proposed method through experiments at a shipyard. The proposed system may be used to enhance the efficiency of press work and is expected to be an effective tool for training beginners in the future.

Ag mesh transparent conductive films (TCFs) were prepared on the commercial FTO/Glass substrate by ultrafast laser direct writing, trying to improve its overall photoelectric performances. The effects of laser scanning speed, laser fluence and Ag mesh height on photoelectric properties of the Ag mesh/FTO TCFs were systematically studied. The results indicated that a small scanning speed or a high laser fluence would cause excessive ablation of the FTO film and result in an increased Ag mesh line width, which was detrimental to the photoelectric properties of the resulting TCF. It was found that the optimal parameters for fabricating Ag mesh/FTO TCFs were a laser scanning speed of 2200 mm/s, a laser fluence of 0.050 J/cm2 and an Ag mesh height of 2500 nm. The as-fabricated TCF possessed the highest figure of merit of 13.03 × 10−2 Ω−1, which was significantly superior to that of the commercial FTO film. Finally, transparent heaters (THs) were prepared respectively based on the optimal Ag mesh/FTO TCF and the FTO/Glass substrate. The Ag mesh/FTO TH exhibited a more excellent heating performance than the FTO TH, further confirming that the overall photoelectric performance of the FTO/Glass substrate had been greatly improved.

Laser-based surface modification methods are employed to augment the surface properties of engineering components. In the presented work, pulsed laser remelting of Ti6Al4V surfaces using a long pulsed laser was used to generate ripple-like micro-features with different feature sizes. The resultant surfaces exhibited improved corrosion and tribocorrosion resistance. Anisotropic wetting characteristics of the laser remelted surfaces led to elongation of water droplets on the surfaces. The osteogenic potential of the surfaces as well as the orientations of human mesenchymal stem cells on the surfaces were dependent on the surface features. On surfaces having 20 μm ripples, differentiation of stem cells towards osteoblastic lineage was higher than that on acid etched surfaces, and the cells were prominently oriented across the ripples, parallel to the laser scanning track. On the other hand, surfaces having 100 μm ripples suppressed the cellular activities on them. While the resistance to corrosion and tribocorrosion of laser remelted surfaces can be attributed to the evolved microstructure and the formation of stable oxide layers, the physical characteristics like topography and wettability dictated cellular behavior on the surfaces. Taken together, the work demonstrates the use of pulsed laser remelting as a simple yet potentially effective route towards manufacturing Ti6Al4V orthopedic implants with improved biofunctionalities.

The process parameters on selective laser sintering (SLS) have a strong effect on part quality. To better understand SLS of composite materials, this study focuses on the influence of laser scan angle and oxygen gas interaction on the mechanical properties, morphology, and joining mechanisms of laser-sintered aluminum-filled polyamide-12 single-layer specimens at room temperature. The results show that the strength and ductility increase with a higher laser scan angle (e.g., near 60°), and the oxygen concentration in the chamber shows a small effect on the elongation. No changes in the morphology and internal structure of the specimens were observed under a different set of process parameters. Additionally, two failure mechanisms were observed; a ductile failure that occurs when particles are well-blended where the metallic particles work effectively hindering crack propagations, and a brittle failure when local amounts of metallic particles are low.

Three-dimensional (3D) information of capturing and reconstructing an object existing in its environment is a big challenge. In this work, we discuss the 3D laser scanning techniques, which can obtain a high density of data points by an accurate and fast method. This work considers the previous developments in this area to propose a developed cost-effective system based on pinhole projection concept and commercial hardware components taking into account the current achieved accuracy. A laser line auto-scanning system was designed to perform close-range 3D reconstructions for home/office objects with high accuracy and resolution. The system changes the laser plane direction with a microcontroller to perform automatic scanning and obtain continuous laser strips for objects’ 3D reconstruction. The system parameters were calibrated with Matlab’s built-in camera calibration toolbox to find camera focal length and optical center constraints. The pinhole projection equation was defined to optimize the prototype rotating axis equation. The developed 3D environmental laser scanner with pinhole projection proved the system’s effectiveness on close-range stationary objects with high resolution and accuracy with a measurement error in the range (0.05–0.25)mm. The 3D point cloud processing of the Matlab computer vision toolbox has been employed to show the 3D object reconstruction and to perform the camera calibration, which improves efficiency and highly simplifies the calibration method. The calibration error is the main error source in the measurements, and the errors of the actual measurement are found to be influenced by several environmental parameters. The presented platform can be equipped with a system of lower power consumption, and compact smaller size

Titanium-based alloy products manufactured by Selective Laser Melting (SLM) have been widely used in biomedical applications, owing to their high biocompatibility, significantly good mechanical properties. In order to improve the Ti–6Al–4V SLM-fabricated part quality and help the manufacturing engineers choose optimal process parameters, an optimization methodology based on an artificial neural network was developed to relate four key process parameters (laser power, laser scanning speed, layer thickness, and hatch distance) and two target properties of a part fabricated by the SLM technique (density ratio and surface roughness). A supervised learning deep neural network based on the backpropagation algorithm was applied to optimize input parameters for a given set of quality part outputs. Several methods were utilized to solve undesired problems occurring during neural network training to increase the model accuracy. The model’s performance was proven with a value of R2 of 99% for both density ratio and surface roughness. A selection system was then built, allowing users to choose the optimal process parameters for fabricated products whose properties meet a specific user requirement. Experiments performed with the optimal process parameters recommended by the optimization system strongly confirmed its reliability by providing the ultimate part qualities nearly identical to those defined by the user with only about 0.9–4.4% of errors at the maximum. Finally, a graphical user interface was developed to facilitate the choice of the optimum process parameters for the desired density ratio and surface roughness.

This paper presents a novel additive manufacturing process, namely the laser melting of polymer-metal colloids (LMC), which is advantageous for repairing features and reducing contamination sources. The developed polymer-metal colloids are conveyed via the designed spindle-driven dispensing system to demonstrate consolidations of the metallic phase onto heterogeneous substrate materials via laser melting. Modelling of the flow rate, velocity and pressure fields is linked to the geometric design of the mechanical devices in the spindle-driven process. The equilibriums of the heat transfer equations in the colloid element were initiated and presented for the estimations of input laser energy. When the input heat was absorbed by the colloid element, the average energy density could be obtained by the ratio of the overall energy density and the engaged laser scanning volume. In the experimental work of the validation tests, the polymer-metal colloid was consolidated on the substrate material with three different results: unconsolidated, partially consolidated and consolidated. The consolidation and bonding of metallic fractions on the heterogeneous substrate materials in the laser melting actions were evaluated and reported.

The dendritic growth transition of nickel-based superalloy in the top region of the laser additive manufactured layer has been studied. The results show that the dendritic growth direction in the top region of the layer is changed from the perpendicular to parallel direction to the laser scanning direction. From the finite element simulation, the dendritic growth transition is found to be attributed to the increased deviation angle between the epitaxial dendritic growth direction and local thermal gradient in the top region of the molten pool. The critical transition angle is revealed to be 70°–80°. The origin of the top transition grains is mostly the re-nucleation sites generated in the last remaining liquid in the top region of the molten pool.

The perfect knowledge about the scanned object’s geometry is essential for the empirical analysis of the stochastic properties of terrestrial laser scanners (TLSs). The Bonn reference wall is intended to be used as a reference for TLS quality investigations. Therefore, it is necessary to know the geometry of the wall at each time of scanning to avoid the misinterpretation of possible movements as systematic effects in the scanner. For this reason, we investigate the stability of the Bonn reference wall in this study. This includes the definition of a geodetic datum, the quantification of displacements, and the establishment of a suited deformation model. Since we discover a movement of about 1 mm within one day and up to 7 mm over the year, it is necessary to establish a cause-response deformation model to correct the wall movements in the scans. This study proposes two dynamic deformation models to compensate for the movements of the wall within one day and within a year. Our results show that it is better to measure the initial geometry of the wall each day since 89 % of the relative movements can be reduced to a maximum of 0.25 mm with a standard deviation of 0.16 mm (0.23 mm without modeling). If the shape is not initially known each day, the standard deviation of the displacements can be reduced from 1.10 mm to 0.61 mm, but the largest residuals still amount up to 2.5 mm, which is not sufficient for stochastic TLS investigations.

Additive manufacturing technique has become one of the more prominent manufacturing techniques over the years. The applications of this manufacturing technique are boundless as new process parameters of the operation affect the new structure of the components and give extended applications. The study experimentally investigates the effects of Ytterbium Laser System process parameters on the resultant microstructure of Ti-6Al-4V grade 5 alloy and reinforcement powders. The deposition process was conducted employing a 3 kW (CW) Ytterbium Laser System (YLS-2000-TR) machine, co-axial to the reinforcement powder. The laser scanning speed and power were varied between the intervals of 0.8–1.0 m/min and 900–1000 W. All other parameters kept constant were the rate of gas flow, the spot diameter, and the rate of powder flow. The composites (Ti-6Al-4V/Ti-Al-Si-Cu) produced by the DLMD technique were analysed using investigative techniques, namely, optical microscopy (OPM), scanning electron microscopy (SEM) aided with energy dispersive microscopy (EDS), X-ray diffraction analysis (XRD), microhardness testing, and corrosion rate analysis. From the analysis of the physical properties, the findings show that the geometric properties such as heat affected zone (HAZ) and dilution ratio of the composite samples were greatly impacted by the increase of the laser power of the DLMD technique, showing an increase in these attributes brought about by the interaction between the laser and the material. The addition of the copper (Cu) element enabled the movement of the copper (Cu) into the titanium (Ti) lattice structure resulting in the formation of beta titanium (β-Ti) microstructure. Increment 54.94% is associated with sample 5A which has the most enhanced microhardness of 770 HV1.0. Sample 6A had shown the most corrosion resistance improvement with 0.00062 mm/year equivalent to 31%.

Large deformations often occur during and after the construction of deep roadways, particularly in fractured hard rock. With persistent deformation, there may be mechanistically unexplained, repeated failure phenomena—they are difficult problems to analyse and address. One strategy is to analyse the failure characteristics of roadways and internal cracking characteristics of the surrounding rock which can be analysed with a digital borehole televiewer and three-dimensional laser scanning equipment. Here, we used this approach combined with research on geostress, joint information, and mechanical properties of rock to reveal the preliminary large deformation mechanism of deep fractured roadways. Based on a cracking-restraint method for engineering design, a control technique is proposed to prevent and control large deformations. The depth and degree of cracking are considered to design parameters and determine the appropriate installation time of the support system. To test this approach, the proposed control technique was applied to a roadway project more than 700 meters deep. The monitoring results demonstrated that this control strategy effectively restrained the cracking of surrounding rocks, improved the quality index of the rock mass, and reduced surface displacement. In addition, due to the improved deformation capacity of the bolt structure, an anti-deformation and energy-absorbing bolt can bear large deformations, preventing premature bolt failures in mining environments.

Verifying geometric compliance in offsite manufacturing (OSM) is key for ensuring adequate fit-up, structural integrity, building system performance, and assembly alignment on site. The use of a ge...

The urgent need to improve performance in the construction industry has led to the adoption of many innovative technologies. 3D laser scanners are amongst the leading technologies being used to capture and process assets or construction project data for use in various applications. Due to its nascent nature, many questions are still unanswered about 3D laser scanning, which in turn contribute to the slow adaptation of the technology. Some of these include the role of 3D laser scanners in capturing and processing raw construction project data. How accurate is the 3D laser scanner or point cloud data? How does laser scanning fit with other wider emerging technologies such as Building Information Modelling (BIM)? This study adopts a proof-of-concept approach, which in addition to answering the afore-mentioned questions, illustrates the application of the technology in practice. The study finds that the quality of the data, commonly referred to as point cloud data is still a major issue as it depends on the distance between the target object and 3D laser scanner’s station. Additionally, the quality of the data is still very dependent on data file sizes and the computational power of the processing machine. Lastly, the connection between laser scanning and BIM approaches is still weak as what can be done with a point cloud data model in a BIM environment is still very limited. The aforementioned findings reinforce existing views on the use of 3D laser scanners in capturing and processing construction project data.

This paper reports an experimental investigation on continuous CO2 laser cutting of polymethylmethacrylate (PMMA) sheet. The influence of four process factors (laser power, cutting speed, assisting gas pressure and sheet thickness) on five process responses (kerf deviation, top heat affected zone, bottom heat affected zone, maximum surface roughness and rough area) has been investigated. The experimental plan was established based on Taguchi L18 mixed design. The kerf geometry and heat affected zones have been measured using polarising light microscopy technique, while the surface roughness was evaluated using 3D laser scanning confocal microscope. Regression models have been derived to correlate different process responses with different process factors. The cut surface could be classified into three zones: rough zone, moderate zone and soft zone. The rough area is increased by increasing gas pressure and laser power and by decreasing the sheet thickness and cutting speed. Increased kerf deviation has been observed at high cutting speed, laser power and gas pressure. High laser power and low cutting speed produced worst surface roughness and wide heat affected zone. Therefore, it is recommended to use low laser power and high cutting speed to minimize the heat affected zone and the surface roughness. However, increasing the cutting speed may result in high kerf deviation.

The measurement of surface moisture on beaches is vital for studying aeolian sand transport mechanisms, but existing techniques are not adequate for monitoring the surface moisture dynamics over a substantial beach section. In this study, we investigated the suitability of a new remote sensing method to monitor the spatiotemporal variation in surface moisture on a sandy beach using a long-range static terrestrial laser scanner (TLS). The TLS was permanently deployed on top of a 42 m high building overlooking the study site at Ostend-Mariakerke, Belgium. Considering the effect of target surface roughness on the intensity and the laboratory’s length limitation, a new intensity correction method is proposed which only uses the field point cloud data measured on a homogenous beach surface (without time-consuming indoor experiments). Based on the corrected intensity data, the relation of the beach surface moisture to the corrected intensity was modeled by an exponential model with a correlation-coefficient squared of 0.92. A moisture estimation model was developed which can directly derive the beach surface moisture from the original intensity data of the TLS with a standard error of 2.27%. The hourly surface moisture dynamics across two tidal cycles on the beach were investigated as a case study, in which the point clouds derived from corresponding unmanned aerial vehicle (UAV) imagery are utilized to improve the calculation accuracy of the incidence angles of TLS point clouds at long distances. Results reveal that, after the intensity correction, the long-range static TLS is an extremely suitable technique to monitor the surface moisture dynamics (daytime and nighttime) over a substantial beach section (hundreds of meters) at a high scanning frequency (minutes to hours).

In dual-phase (DP) steels, the morphology, distribution, and volume fraction of the martensite phase affect several properties of the metal. In this work, the DP600 steel was laser treated using an Yb:fiber laser with different process parameters. The objective was to map the laser surface hardening and construct a process chart. Additionally, force spectroscopy was proposed to evaluate microstructural phases stiffness. The elastic constant of ferrite from both the base material and the laser treated area was approximately the same, about 20% lower than that of martensite from the treated area. From the processes chart, conclusion was more intense hardening, with needle-like structures, but in thinner layers, requires specific energies of about 2.0 kJ/cm2, while greater volume of martensitic phase is accomplished at 4.0 kJ/cm2. Tensile yield increased 30%, though tensile strength augmented 5–10%. In addition, lower laser scanning velocities was more suitable to obtain greater volumes of martensite.

The use of laser scanning in the realm of bridge assessment has been primarily limited to measuring large bridge dimensions. Given the scale of these measurements compared to standard accuracy metr...

International audience; The 3-D information collected from sample plots is significant for forest inventories. Terrestrial laser scanning (TLS) has been demonstrated to be an effective device in data acquisition of forest plots. Although TLS is able to achieve precise measurements, multiple scans are usually necessary to collect more detailed data, which generally requires more time in scan preparation and field data acquisition. In contrast, mobile laser scanning (MLS) is being increasingly utilized in mapping due to its mobility. However, the geometrical peculiarity of forests introduces challenges. In this article, a test backpack-based MLS system, i.e., backpack laser scanning (BLS), is designed for forest plot mapping without a global navigation satellite system/inertial measurement unit (GNSS-IMU) system. To achieve accurate matching, this article proposes to combine the line and point features for calculating transformation, in which the line feature is derived from trunk skeletons. Then, a scan-to-map matching strategy is proposed for correcting positional drift. Finally, this article evaluates the effectiveness and the mapping accuracy of the proposed method in forest sample plots. The experimental results indicate that the proposed method achieves accurate forest plot mapping using the BLS; meanwhile, compared to the existing methods, the proposed method utilizes the geometric attributes of the trees and reaches a lower mapping error, in which the mean errors and the root square mean errors for the horizontal/vertical direction in plots are less than 3 cm.

Alongside spatial information, an intensity scalar is also measured by LiDAR (Light Detection And Ranging) sensor systems. It corresponds to the amplitude of the backscattered laser beam after reflection on the scanned surface. This information isn’t directly usable due to dependencies of geometrical parameters occurring during the scanning process and additional processing modifications. The research community, in a growing trend, invests efforts to convert this signal into a value which could bring qualitative and quantitative new applications. We propose in this paper, a review of the theortical background of LiDAR radiometric calibration, from physical background to state-of-art methodology. A comparison of two approaches to eliminate geometrical (range and incidence angle) and instrumental dependencies of intensity measurement is presented. Their application on several homogeneous areas of a real-world case study shows a significant reduction of intensity variation between surfaces with identical material composition. Finally, a linearization process permits to obtain an equivalent Lambertian reflectance value which, by its disciminant potential, could be specifically suitable for some algorithms like segmentation or registration.