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The present study investigates the impact of different heat transfer approaches on the precision of geometry and solidification behavior in additively manufactured thin clad walls. Employing a 2D laser scanner to assess dimensional accuracy, the study demonstrates that thin clad walls produced on a copper base plate with forced air convection exhibit notably superior accuracy compared to those on a mild steel substrate with natural convection. Microstructure analysis unveils distinct characteristics: Thin clad walls printed with natural convection on mild steel display a coarse columnar dendritic structure marked by increasing primary dendrite arm spacing (PDAS) from bottom to top (10.4 ± 0.7 to 14.5 ± 3 µm). In contrast, forced convection leads to a fine cellular and columnar dendritic microstructure with minor PDAS variation (4.6 ± 0.9 to 7.4 ± 1.7 µm) along the entire vertical span. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiaotong University (Science) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Building information modeling (BIM) can greatly improve the management and planning of historic building conservation projects. However, implementing BIM in the heritage has many challenges, including issues with modeling irregular features, surveying data occlusions, and a lack of predefined libraries of parametric objects. Indeed, surface features can be manually distinguished and segmented depending on the level of human involvement during data scanning and BIM processing. This requires a significant amount of time and resources, as well as the risk of making too subjective decisions. To address these bottlenecks and improve BIM digitization of building geometry, a novel deep learning based scan-to-HBIM workflow is used during the recording of the historic building in historic Jeddah, Saudi Arabia, a UNESCO World Heritage site. The proposed workflow enables access to laser scanner and unmanned aerial vehicle imagery data to create a complete integrated survey using high-resolution imagery acquired independently at the best position and time for proper radiometric information to depict the surface features. By employing deep learning with orthophotos, the method significantly improves the interpretation of spatial weathering forms and façade degradation. Additionally, an HBIM library for Saudi Hijazi architectural elements is created, and the vector data derived from deep learning-based segmentation are accurately mapped onto the HBIM geometry with relevant statistical parameters. The findings give stakeholders an effective tool for identifying the types, nature, and spatial extent of façade degradation to investigate and monitor the structure. [ABSTRACT FROM AUTHOR]

Heritage buildings represent history and act as vessels of human civilisation. The significance of these architectural phenomena increases as society increases, which renders their preservation and ethical use increasingly crucial. Hence, preserving heritage buildings is necessary for societal benefit. The accuracy of three-dimensional (3D) point cloud models of heritage buildings is important to their digital conservation. Traditional mapping methods typically require more time and human resources. Furthermore, the outcome is subject to measurement omissions, errors, and other issues, which are contrary to the protection of the object measured. The complex elements of ancient Chinese architecture render it challenging for traditional measuring techniques to accurately capture spatial structural information. The 3D laser scanning technology is a novel technology to obtain 3D data rapidly. In this paper, the Great Achievement Palace of the Confucian Temple in Yuci District, Jinzhong City, Shanxi Province, was used as an example to examine the application of 3D laser scanning technology to acquire point cloud models of heritage buildings. Field data collection for architectural heritage using 3D laser scanning technology requires measuring station setting analysis to ensure effect accuracy while considering the elements of target location and quantity. For the 3D point cloud model of the Great Achievement Palace, error analysis and accuracy assessment were conducted on the quality elements of alignment accuracy between scanning stations, point cloud model reliability, point cloud data noise condition, and whether the point cloud data were stratified. The findings demonstrated that the improved method quickly and accurately acquired 3D point cloud model data and obtained realistic spatial data models of the heritage building. [ABSTRACT FROM AUTHOR]

Knowledge of fracture properties and associated flow processes is important for geoscience applications such as nuclear waste disposal, geothermal energy and hydrocarbons. An important tool established in recent years are hydro-mechanical models which provide a useful alternative to experimental methods determining single fracture parameters such as hydraulic aperture. A crucial issue for meaningful numerical modeling is precise imaging of the fracture surfaces to capture geometrical information. Hence, we apply and compare three distinct fracture surface imaging methods: (1) handheld laser scanner (HLS), (2) mounted laser scanner (MLS) and (3) Structure from Motion (SfM) to a bedding plane fracture of sandstone. The imaging reveals that the resolution of the fracture surface obtained from handheld laser scanner (HLS) is insufficient for any numerical simulations, which was therefore rejected. The remaining surfaces are subsequently matched and the resulting fracture dataset is used for detailed fracture flow simulations. The resulting hydraulic aperture is calibrated with laboratory measurements using a handheld air permeameter. The air permeameter data provide a hydraulic aperture of 81 ± 1 µm. For calibration, mechanical aperture fields are calculated using stepwise increasing contact areas up to 15%. At 5% contact area, the average hydraulic aperture obtained by MLS (85 µm) is close to the measurement. For SfM, the measurements are fitted at 7% contact area (83 µm). The flow simulations reveal preferential flow through major channels that are structurally and geometrically predefined. Thus, this study illustrates that resolution and accuracy of the imaging device strongly affect the quality of fluid flow simulations and that SfM provides a promising low-cost method for fracture imaging on cores or even outcrops. Highlights: We evaluate a handheld laser scanner, a mounted laser scanner and the Structure from Motion method for imaging of fracture surfaces. We use the scanned geometries for flow simulations and calibrate the results with air permeameter measurements. Our study reveals that the handheld laser scanner is unsuitable for fracture surface imaging due to low resolution and accuracy. The simulations performed with geometries obtained by the mounted laser scanner and the Structure from Motion method provided comparable results. The Structure from Motion method seems to be promising for fracture investigations in field applications due to the high flexibility and low costs. [ABSTRACT FROM AUTHOR]

As climate changes, maintenance of yield stability requires efficient selection for drought tolerance. Drought-tolerant cultivars have been successfully but slowly bred by yield-based selection in arid environments. Marker-assisted selection accelerates breeding but is less effective for polygenic traits. Therefore, we investigated a selection based on phenotypic markers derived from automatic phenotyping systems. Our trial comprised 64 potato genotypes previously characterised for drought tolerance in ten trials representing Central European drought stress scenarios. In two trials, an automobile LIDAR system continuously monitored shoot development under optimal (C) and reduced (S) water supply. Six 3D images per day provided time courses of plant height (PH), leaf area (A3D), projected leaf area (A2D) and leaf angle (LA). The evaluation workflow employed logistic regression to estimate initial slope (k), inflection point (Tm) and maximum (Mx) for the growth curves of PH and A2D. Genotype × environment interaction affected all parameters significantly. Tm(A2D)s and Mx(A2D)s correlated significantly positive with drought tolerance, and Mx(PH)s correlated negatively. Drought tolerance was not associated with LAc, but correlated significantly with the LAs during late night and at dawn. Drought-tolerant genotypes had a lower LAs than drought-sensitive genotypes, thus resembling unstressed plants. The decision tree model selected Tm(A2D)s and Mx(PH)c as the most important parameters for tolerance class prediction. The model predicted sensitive genotypes more reliably than tolerant genotype and may thus complement the previously published model based on leaf metabolites/transcripts. [ABSTRACT FROM AUTHOR]

Recent advances in the use of remote sensing techniques allow the acquisition of dense 3D information helpful for the characterization of the rock mass joints. This implies the necessity of having robust and reliable methods to evaluate and extract the primitive geometries representing discontinuities on a rock outcrop. Moreover, these methods have to be easy to use, fast and accurate, which leads nowadays to the tendency of developing automated methods, often having limitations as concerns processing time, definition of parameters and, especially, accuracy. We present here an alternative approach based on two new semi-automatic algorithms, the Iterative Pole Density Estimation (IPDE) and the Supervised Set Extraction (SSE), used in combination with well-known and suitable clustering and density estimation methods. The IPDE performs an analysis based on a threshold value, within which it searches for coplanar points in a range of tolerance, automatically eliminating those below the established threshold, and then finding principal orientations by Kernel Density Estimation (KDE) and identifying clusters by a manual evaluation or through automated clustering methods. The SSE is a tool that allows to extract discontinuity sets from point clouds through an approach aimed to combine observations made in situ with digital results, taking into account the crucial importance of traditional analysis by an expert user. The method was tested in Campania (Italy) at the Cocceio Cave and at the Cetara Tower cliff: at the cave, we were able to recognize an additional set, not identified during previous digital analysis. In the second case, a fully automatic technique, with little or no human intervention on the point cloud, was compared with a previously made supervised method to perform the semi-automatic approach, eventually checking both results with those from traditional surveys, which led the whole analysis to shift the focus on the combined method proposed. [ABSTRACT FROM AUTHOR]

The study highlights the significance of combining imaging and laser scanning techniques to enrich point clouds used for reliable documentation and Heritage Building Information Modeling (HBIM). The fusion-based approach was used to document Al Ula Heritage site in Saudi Arabia, a UNESCO World Heritage Site with well-preserved tombs from the first century BC. The HBIM parametric modeling process requires a detailed survey to collect all geometric data. Although terrestrial laser scanners (TLS) are an efficient tool for 3D recording of heritage scenes in a short period of time, the data resolution is insufficient for identifying and evaluating the spatial distribution of surface weathering forms. Furthermore, combining scans collected at different times may pose difficulties in recording the texture. These issues have an impact on the subsequent 3D modeling phase as well as the efficiency of interpreting and tracing surface features in the Scan-to-BIM process. The proposed workflow using imagery data to enhance both the geometry and coloring of laser point clouds. In addition to texture mapping, the high-resolution imagery is used to densify the laser data using dense image matching, allowing for a clear reading of the surface features, and serving as a useful tool to identify the type, extent, and severity of façade damage. TLS and imagery data were collected separately, with images taken at the best time and location for realistically recording of surface details. Finally, the captured images are orthorectified by TLS geometric information and used for HBIM texturing to provide realistic decay mapping. The results showed that the combination of TLS and photogrammetry allowed for the efficient collection of 3D data, which improved tracing and digitizing HBIM with complete mapping information. The research findings will be greatly useful in the management and planning of historic building conservation and restoration projects. [ABSTRACT FROM AUTHOR]

Thanks to recent technological innovations, some large-volume-metrology measuring instruments—that would have been considered out of context one/two decades ago—are now effective for the shipbuilding industry, where dimensional errors of a few millimetres are generally tolerated. This paper considers three state-of-the-art instruments: a laser tracker, a total station, and a laser scanner, all with the latest generation of technology. While the first instrument type has long been widespread for applications in industrial metrology, the last two have traditionally been used in other fields, such as as-built surveying, civil engineering, architecture and topography. Instruments are compared using experimental tests concerning the dimensional verification of cruise-ship modules in the relatively under-explored context of the construction of the hull, which represents the ship's framework. The comparison is structured based on several qualitative and quantitative criteria, including but not limited to (i) simplicity of use for operator(s), (ii) time of acquisition/analysis of measurement data, (iii) metrological performance, and (iv) cost. The main contribution of this article is the on-site testing of instruments of interest, in the typical (unfavourable) working conditions of shipyards. [ABSTRACT FROM AUTHOR]

This work proposes a novel visual pose tracking method for on-orbit uncooperative targets by making use of fused data from 3D laser scanner and optical camera. In particular, the target point cloud from the laser scanner is precisely segmented by K-means cluster methods, and projected on the pixel grid to extract accurate depth information. The obtained depth information is fused with the target feature point of the optical images, which then is used to estimate the relative pose for tracking tasks. Different with the RGB-D camera or other sensor fusion method, the proposed tracking method can maintain a robust and accurate tracking performance even in presence of large background interference in the images. The proposed visual tracking method was comprehensively tested with two different datasets, the synthetic images without background interference and the standard satellite dataset with large background interference. With comparisons with other sensor fusion methods based on images and 3D point cloud, the proposed fusion method show more robust and accurate performance. [ABSTRACT FROM AUTHOR]

Open-die forging is used to manufacture heavy durable parts such as shafts. In-process measurements are required for shape correction. The passive 3D measurement method is based on forging silhouettes in images and has demonstrated its advantages in this application. However, when using two cameras, only four tangents are available to determine the cross-section. In this paper, we propose a novel multi-camera multi-observation method for forging measurements; it increases the number of tangent lines used to determine the forging cross-section. The results suggest a decrease in measurement error proportional to the square root of the observation number. The six-observation precision is ± 0.5 mm in a measurement volume of 6 × 6 × 2 m for axis straightness and diameter measurements (95% confidence interval). However, many outliers remain in case of diameter measurement. In addition, the forging circularity can be measured. The proposed system shows good agreement with the laser scanning measurement method. Overall, the system has considerable potential for forging manufacturing applications. [ABSTRACT FROM AUTHOR]

Mobile light detection and ranging (LiDAR) scanning systems consist of global navigation satellite system (GNSS) and inertial navigation system (INS) equipment for positioning in addition to LiDAR sensors and cameras. All of these units work collaboratively to generate an accurate point cloud positioned in a three-dimensional (3D) geodetic coordinate system. However, various factors affect the measurement quality with mobile LiDAR systems (MLS), and these factors include inertial drift problems, GNSS positioning errors, errors stemming from insufficient calibration, etc. The measurements with multiple scanners in mobile systems require a calibration process to deal with the inconsistency problem in overlapping strips. The calibration is done between the laser, camera, INS, and GNSS sensors. The cameras and laser scanners become ready to use after the calibration stage. The strip adjustment is a crucial process for eliminating the errors, which come from the GNSS/INS measurements and remain despite the calibration process, in obtaining an accurate point cloud of the scanned structure. This study aims testing and clarifying the performance of the iterative closest point (ICP) algorithm in precise registration of LiDAR strips and hence proposes a data-driven approach for strip adjustment in mobile LiDAR scanning applications. In the result of the numerical case study, fine registration of the point clouds obtained from forward and backward scanning using ICP yields a 3.2 cm root mean square error and 1.5 cm mean difference, which corresponds to an almost 84% improvement in mean differences of the point clouds in comparison to the initial phase before the ICP registration. Thus, the results clarify that the ICP algorithm succeeds in the strip adjustment process by reducing the average difference between the mutual points of multi-strip point clouds in mobile LiDAR applications. [ABSTRACT FROM AUTHOR]

Relative settlement between bases of a building is resource of the danger on the structures hence leads to life loss. Unwanted differential settlement under the bases might happen due to change of the loads value and underlying ground due to environmental changes. This settlement generated additional stresses in columns, beams, and distortion of the building members. This research gets down to test a three-dimensional structure consisted of a slab, beams, and columns based on isolated footings, one of them supporting on loose sandy soil to control in the column settlement. Width of the structure was 2 m in both directions, while the total height was 2.13 m. The thickness of the slab was 80 mm. The slab supported on four identical beams which had a cross section of 100 × 230 mm, while the net span was 1600 mm. The column had square cross section of 200 × 200 mm, while its length between the footing surface and the beam soffit was 1500 mm. Area of the footing was 500 × 500 mm, while the depth was 400 mm. A uniformly distributed sand weight of 8 tons was accentuated above the structure slab where the loading rate was 250 kg/m2 per hour. Two surveying equipment (total station and laser scanner) were used to monitor three-dimensional deformations of the members due to self-weight, 8 tons and movement down one of the columns. Cracks, subsidence, marbling, deformation, and drawing out images of the structure before and after loading were studied, as well as differential settlement of footings. The results showed that coordinates of all deformations for laser scanner and total station are very close. Differential settlement of the columns caused many following damages: (1) additional settlement in nearby columns, (2) diagonal cracks in the slab, (3) shear cracks in the beams, (4) horizontal cracks in the adjacent columns, (5) additional deflection in the slab, and in the beams which reached 100 and 300% more than deflection due to loading by 8 tons, while deflection of other two beams is not noticeable affected. Although the differential settlement of the footings due to self-weight reached 100%, the structural members did not crack. Despite, the column movement due to sand weight of 8 tons reached 150% bigger than that of other columns, and no cracks took place in the members. [ABSTRACT FROM AUTHOR]

The outer dimensions and 3D model of ring forgings in industrial production are the important parameters to ensure the quality of the products. In order to realize the measurement of the outer dimensions and 3D model of the ring forgings, a measuring method for the ring forgings combining with a CCD camera and a 2D laser scanner is proposed in this paper. Firstly, the image information of the ring forgings is obtained by the CCD camera. The radiuses of different sections for ring forgings are acquired by pixel calibration and edge detection. Secondly, the point cloud data of different sections are obtained by laser scanner with the movement of the transmission mechanism. Then, the position discrimination method of straight line fitting is used to reduce the error data. And the radius matching method is used in the further processing of the point cloud data based on image detection, and the point cloud data with high accuracy is further extracted. Finally, the 3D point cloud data and 3D model of the ring forgings are obtained by rotating the 2D point cloud data. The outer dimensions of forgings are derived from the 3D model. The experiments were carried out with two different ring forgings. According to the experimental results, the feasibility of the method proposed in this paper is verified. [ABSTRACT FROM AUTHOR]

With a growth tendency, the employment of the Adaptive Monte Carlo Localization (AMCL) Robot Operational System (ROS) package does not reflect a more in-depth discussion on its parameters' tuning process. The authors usually do not describe it. This work aims to extend the analysis of the package's parameters' distinct influence in an automated guided vehicle (AGV) indoor localization. The experiments test parameters of the filter, the laser model, and the odometry model. Extending the previous analysis of seven parameters, the present research discusses another ten from the 22 configurable parameters of the package. An external visual vehicle pose tracking is used to compare the pose estimation from the localization package. Although the article does not propose the best parameter tuning, its results discuss how each tested parameter affects the localization. The paper's contribution is discussing the parameters' variation impact on the AGV localization using the covariance matrix results. It may help new researchers in the AMCL ROS package parameter tuning process. The results show minor changes in the default parameters which can improve the localization results, even modifying one parameter at a time. [ABSTRACT FROM AUTHOR]

Purpose: Robotic systems have the potential to overcome inherent limitations of humans and offer substantial advantages to patients including reduction in surgery time. Our group has undertaken the challenge of developing autonomous wound closure system. One of the initial steps is to allow accurate assessment of wound skin topology and wound edge location. We present a vision-laser scanner to generate 3D point cloud for 3D reconstruction of wound's edge and topology. Methods: When the laser range sensor measures Z coordinate, two encoders installed on the actuators of the gantry robot provide the precision values of X, Y coordinates simultaneously. The 3D point cloud of the wound skin is generated by recordings of X, Y and Z during scanning is performed over wound skin surface. To reduce the scanning time, we exploit a supplementary laser LED to project a regular laser spot on the wound skin surface, which can provide an additional measurement point by incorporating artificial neural network estimation approach. In the meantime, the point cloud of the wound edge can be extracted by detecting if the laser spot is located on the wound edge in the image from 2D camera. Results: The mean absolute error (MAE) and standard deviation (σ) of wound edge are measured in MeshLab environment. The MAE (σ) in X (tangent), Y (tangent), and Z (normal) are 0.32 (0.22) mm, 0.37 (0.34) mm, and 0.61 (0.29) mm, respectively. The experimental results demonstrate that the vision-laser scanner attains high accuracy in determining wound edge location along the tangent of the wound skin. Conclusion: A vision-laser scanner is developed for 3D reconstruction of wound's edge and topology. The experimental tests on the different wound models revealed the effectiveness of the vision-laser scanner. The proposed scanner can generate 3D point cloud of the wound skin and its edge simultaneously, and thus significantly improve the accuracy of wound closure in clinical applications. [ABSTRACT FROM AUTHOR]

The research presented in this paper is aimed at testing an innovative surveying protocol based the integration of quick methodologies employed for the characterization of a carbonate cliff affected by a rockfall and showing signs of further instability. During a post-rockfall emergency, one of the most important activities is evaluating if reactivation of the movements is possible, and if it may represent a threat for a series of elements at risk. On 5 January 2019, intense rainfalls triggered the detachment of a significant volume of fractured limestone and dolostone below the main square of a historical village located in southern Italy in the municipality of Messina, giving rise to one of the greatest landslides occurred at one of the most tourist areas of northeastern Sicily. Fallen blocks damaged the two main infrastructures of the area reaching also a bus terminal, which fortunately was vacant at the time of the rockfall. With the aim of proposing a quick surveying protocol during a post-rockfall emergency, terrestrial laser scanner, infrared thermography, and horizontal to vertical spectral ratio surveys were employed for the geostructural characterization of the cliff and for the investigation of the subsoil below the main square. In particular, the survey through terrestrial laser scanner returned an accurate 3D model of the cliff, where some key structures were highlighted; infrared thermography allowed recognizing caves and fractures along the cliff, with specific reference to a hollow area arising from past rockfalls. Such remote data, along with direct rock mass surveys performed by expert climbers allowed ascertaining that the instability of this cliff is driven by wedges formed by the intersection of 2 and 3 discontinuity systems, which are likely related to the main tectonic systems of the area. The horizontal to vertical spectral ratio survey allowed the identification of a peculiar vertical contrast of impedance, which may be related to a mechanical discontinuity located below the main square of the village, well matching with one of the systems responsible of the instability. The integration of these surveys methodologies resulted a useful quick protocol for the achievement of the key information on the stability of a rock cliff in the initial stage of its securing. [ABSTRACT FROM AUTHOR]

Coastal cliffs are subject to erosion processes of continental and marine nature, whose assessment is particularly challenging given the inaccessibility of these landforms and the episodic and irregular nature of their evolution. For this reason, diverse techniques have been developed over the last decades to monitor coastal cliff changes. In this work, three monitoring methods are applied to the Torre Bermeja coastal cliff (South Spain), a conglomeratic Plio-Pleistocene cliff whose instability poses a threat to people walking along the fronting beach. Conventional aerial photogrammetry (AP), structure-from-motion terrestrial photogrammetry (SfM-TP) and terrestrial laser scanning (TLS) are applied on two sites and compared in terms of erosion rates obtained, advantages and disadvantages, uncertainties involved and key aspects to be considered in planning surveys. Results obtained by aerial photographs indicate an average recession rate of the cliff foot around 0.15 m/year over the last 40 years, with a high spatial variability and an associated uncertainty of 0.1 m/year. The use of SfM-TP along an 8-month period yielded an average erosion rate of the cliff face around 2.8 mm/day in one of the sites, mainly related to a large rockfall, and around 0.5 mm/day in the other site, implying an annual recession rate of 0.18 m/year. Results of TLS are very similar to those of SfM-TP. The data show that AP is only convenient for a general evaluation of medium-term cliff evolution along large coastal stretches, while both SfM-TP and TLS can be used for a detailed investigation of erosion processes and for the quantification of local-scale morphological changes. SfM-TP and TLS allowed obtaining high-resolution 3D models of the cliff, with negligible differences between the surfaces generated by SfM-TP point clouds and by TLS meshes. The main advantages observed in SfM-TP are the low cost of the equipment and the easier and faster data collection in the field when compared with TLS. This allows the monitoring of cliff changes with a high temporal resolution, in order to assess cliff response to external forcing. The main advantages found in TLS are the better representation of shadow areas and shorter post-processing times. [ABSTRACT FROM AUTHOR]

Spatial change detection is a fundamental technique for finding the differences between two or more pieces of geometrical information. This technique is critical in some robotic applications, such as search and rescue, security, and surveillance. In these applications, it is desirable to find the differences quickly and robustly. The present paper proposes a fast and robust spatial change detection technique for a mobile robot using an on-board range sensors and a highly precise 3D map created by a 3D laser scanner. This technique first converts point clouds in a map and measured data to grid data (ND voxels) using normal distributions transform. The voxels in the map and the measured data are then compared according to the features of the ND voxels. Three techniques are introduced to make the proposed system robust for noise, that is, classification of point distribution, overlapping of voxels, and voting using consecutive sensing. The present paper shows the results of indoor and outdoor experiments using an RGB-D camera and an omni-directional laser scanner mounted on a mobile robot to confirm the performance of the proposed technique. [ABSTRACT FROM AUTHOR]

Copyright of Gesunde Pflanzen is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using laser scanner data, an exhaustive rockfall database has been established for a rockwall located near the town of Grenoble (France). The study site is a long double cliff, on the eastern border of the Chartreuse Massif. The two cliffs consist respectively of thinly bedded and massive limestone, which show different structures, morphologies and rockfall activities. The 3D point clouds obtained by laser scanner allow to detect and model the fallen compartments in 3D. Information about cliff surface, and localization, dimensions, failure mechanism for each compartment were obtained and analyzed in order to characterize the morphological evolutions of the cliffs. It appears that the morphology and the slope of the lower cliff is related to fracturing and torrential erosion which occurs in the marls below the cliff, showing a rockfall frequency 22 times higher than for the upper cliff. These results show that the erosion process in the lower cliff is in a transient state, whereas it could be in a steady state in the upper cliff. Rockfalls have been dated by a near-continuous photographic survey (1 photo each 10 mn) and a monthly survey during 2.5 years. The analysis of the two data bases shows that the rockfall frequency is 7 times higher during freeze-thaw episodes than without meteorological event, and 4.5 times higher during rainfall episodes. Moreover, it becomes 26 times higher when the mean rainfall intensity is higher than 5 mm/h. Based on these results, a 3-level hazard scale has been proposed for hazard prediction. [ABSTRACT FROM AUTHOR]

For years, the Laboratory of Geomatics of the Mediterranean University of Reggio Calabria has undertaken an interdisciplinary project for the recovery and dissemination of information regarding the cultural-artistic and archeological heritage of the metropolitan area. The combined use of geomatics technologies (laser scanners, GPS positioning, digital photogrammetry, remote sensing, GPR) allows on the one hand to investigate objects and artifacts, providing metric, form, and location information; and on the other, to catalog information and make it accessible to the community. Indeed, the digitalization and reconstruction tools of 3D models can be the answer to the limits related to communicability in the archeological sector. Precision, detail, and very accurate photo-realistic reconstructions are particularly useful for virtual and augmented reality applications, integrating them in the devices used on a daily basis. The present note concerns, therefore, the acquisition of information using the point cloud from UAVs and laser scanners, the subsequent 3D modeling, and their representation in an augmented reality (AR) environment using mobile platforms. The application was tested on the church of Sant’Antonio Abate, located in the North of Reggio Calabria, which according to studies is the only evidence of medieval architecture in the territory of Reggio Calabria. [ABSTRACT FROM AUTHOR]

The new geomatics techniques have the aim of responding to the needs of damage documentation, risk assessment and providing support for managing and sharing data in emergency and danger conditions. The paper describes the experience of a group of researchers in geomatics and construction techniques at the Iuav University of Venice following the Emilia earthquake, when on 20th and 29th of May 2012, two powerful earthquakes struck northern Italy. The epicentres were recorded respectively in Finale Emilia (magnitude 5.9 Ml) and Medolla (magnitude 5.8 Ml) in the province of Modena, though the earthquake was formed by a series of seismic shakes located in the district of the Emilian Po Valley, mainly in the provinces of Modena, Ferrara, Mantova, Reggio Emilia, Bologna and Rovigo. An immediate documentation was necessary to shoring up and protect the damaged structures before any restoration and reconstruction intervention. Many monuments in the city of Mantova were hit by the earthquake and, among these, Palazzo Ducale with the well-known Castello di San Giorgio which host the noteworthy “Camera degli Sposi”. This building, the most famous of the city, was so damaged that it was closed for more than 1 year after the earthquake. Immediately after the earthquake, the Soprintendenza per i Beni Architettonici e Paesaggistici of Brescia, Cremona and Mantova establish an agreement with the University Iuav of Venice, requiring an analysis and assessment of the damage in order to proceed with the development of an intervention project. This activity turned out to be very important not only from the point of view of the recovery of the architectural and artistic heritage but also because the city’s economy is based primarily on tourism. The closure of one of the most important monuments of Mantova has led to a significant and alarming decline in the government income. [ABSTRACT FROM AUTHOR]

Digital survey techniques are well established in the cultural and archaeological heritage fields and they have been used by us to document, study and promote knowledge on ancient ships and wooden boats. In this paper, we want to show four case studies with different peculiarity on which digital techniques have been applied: (1) ‘Comacchio sewn boat’, discovered in a land excavation site. (2) ‘Ercolano boat’, restored and exposed in a museum. (3) ‘Trabaccolo Nuovo Trionfo’, historical carriage boat of High-Adriatic sea. (4) Wooden scaled model of ‘brick Cygne’. These represent a peculiar application, complicated by the specific nature of the material of the boats, due to the structural stability and the shape of the wood that could be compromised in an aerobic environment. The archaeologists have the responsibility to employ a fast documentation, but with the correct precision and accuracy for the nominal scale of the survey; the use of digital imaging and survey techniques supports the researchers, such as video and photograph recording, multi-image photogrammetry and laser scanning, and the subsequent elaboration of a virtual 3D model of the real surveyed artefact. This allows scrupulous study of ancient naval construction from both a scientific and disseminative point of view to take place, permitting to increase the knowledge and perception by the general public of this important archaeological and historical heritage. [ABSTRACT FROM AUTHOR]

Vine vigour assessment has been a major concern of precision viticulture studies in order to identify areas of uniform vine performance within vineyards. Moreover, the counting and weighing of winter dormant canes is considered as the most informative measurement to indicate vine balance and is commonly performed manually by grape growers for management purposes. The main concern of this measurement is that it is time consuming and laborious and it cannot accommodate detailed sampling density. In the present study, the potential of using laser scanner technology as an automated, easy and rapid way to perform mapping of the winter pruning wood across the vineyard was investigated. The study was conducted during 2010 and 2011, in a one hectare commercial vineyard in central Greece, planted with cv. Agiorgitiko, a traditional Greek variety for the production of red wine. Parameters of topography, soil depth, soil texture, canopy properties (NDVI), yield, and grape quality were mapped and analysed in conjunction to winter canes weighing at pruning time. The mapping of the dormant canes was carried out using a 2D laser scanner sensor prior to pruning and manually measuring the pruning weight on a 10 9 20 m grid. Laser scanner measurements showed significant relationship in both 2010 and 2011 with pruning weight (r = 0.809 and r = 0.829 respectively, p < 0.001), yield and early season NDVI, showing the potential of using laser scanner measurements to assess variability in vine vigour within vineyards. These results suggest that laser scanners offer great promise to characterize within field variability in vine performance. [ABSTRACT FROM AUTHOR]

Steric analysis of morphological changes is important for evaluation of surgical techniques. This study was performed to assess the measurement accuracy of alveolar soft tissue contour with a laboratory laser scanner. The width of the maxillary alveolar soft tissue contour was evaluated in 20 volunteers. Measurement sites were established in the alveolar soft tissue contour of the maxillary incisor and canine areas. Each site was evaluated by direct measurement with a microcaliper for each subject (DMM) and image measurement using a laboratory laser scanner (IMS). The accuracy of measurement methods was evaluated. Additionally, two plaster models obtained from the same subjects were scanned and superimposed, and the nonoverlapping areas were measured. Each measurement method exhibited a strong correlation (r = 0.89). The interclass correlation coefficient (single measure) between examiners was also high for each measurement method (PMM 0.978; IMS 0.997). In the superimposed images of the two plaster models, the distance of the nonoverlapping region was only 0.06 ± 0.08 mm in the labial aspect and 0.07 ± 0.09 mm in the palatal aspect. The image measurement of the scanning data shows high accuracy in evaluation of the alveolar soft tissue contour. This technique is useful for evaluation of chronological changes in the alveolar contour after soft and hard tissue augmentation. [ABSTRACT FROM AUTHOR]

Within an interdisciplinary project to study Istanbul’s Hagia Sofia, a georadar survey was carried out in the central nave to assess if the deformations of the structure previously observed could be related to a differential behavior of the subsoil caused by architectural remains underneath. This study faces an unusual challenge since it was necessary to study the space beneath the scaffolding placed for the restoration works. The survey of the central nave was successful and allowed the detection of remains of walls that probably formed the basement of a previous 18- by 22-m structure. In addition, another interesting feature was discovered 2 m below the marble mosaic in the southeastern part of the nave. Although it is not possible to define its function, it seems that there could be a close relationship between this 2- by 3-m buried structure and the marble mosaic in the floor surface. Although some structures were identified under the floor of Hagia Sofia, there are no major changes in the topography of the central nave floor. [ABSTRACT FROM AUTHOR]

Shear strength parameters ( c, φ) of a structural plane are the key factors for the stability assessment of rock masses. The shear strength parameters are obtained by a structure plane shear test carried out in laboratory. However, it is difficult to obtain test samples with the same surface morphology and to remove the effect of surface irregularity from test results. Based on the similarity principle and orthogonal test, this paper presents a new model preparation method for structural planes using a high-strength mold mixture material. Firstly, the original morphology of the structural plane is recorded by in situ measurement using a laser device and then the mold of the structural plane is reproduced using a 3D printer. Subsequently, a mix proportion test of the high-strength mold material is conducted using the orthogonal test, and the model of the structural plane is prepared by pouring this high-strength mixture material into the 3D mold. Ultimately, the shear strength parameters of this high-strength structural plane replica are obtained using a shear box test in the laboratory. The proposed method has particular advantages such as the preparation of multiple replicas for structure planes and the ability to obtain repeatable results. [ABSTRACT FROM AUTHOR]

In this research, methods and algorithms of calibration of optical schemes and elements of a triangulation laser system were analyzed. Recommendations for precision enhancement of an optical system are further used in improving parameters of a laser and reverse engineering they are also implemented in engineering of a high-speed linear laser 3D scanner. [ABSTRACT FROM AUTHOR]

Multi-modal sensory data plays an important role in many computer vision and robotics tasks. One popular multi-modal pair is cameras and laser scanners. To overlay and jointly use the data from both modalities, it is necessary to calibrate the sensors, i.e., to obtain the spatial relation between the sensors. Computing such a calibration is challenging as both sensors provide quite different data: cameras yield color or brightness information, laser scanners yield 3-D points. However, several laser scanners additionally provide reflectances, which turn out to make calibration to a camera well feasible. To this end, we first estimate a rough alignment of the coordinate systems of both modalities. Then, we use the laser scanner reflectances to compute a virtual image of the scene. Stereo calibration on the virtual image and the camera image are then used to compute a refined, high-accuracy calibration. It is encouraging that the accuracies in our experiments are comparable to camera-camera stereo setups and outperform another of other target-based calibration approach. This shows that the proposed algorithm reliably integrates the point cloud with the intensity image. As an example application, we use the calibration results to obtain ground-truth distance images for range cameras. Furthermore, we utilize this data to investigate the accuracy of the Microsoft Kinect V2 time-of-flight and the Intel RealSense R200 structured light camera. [ABSTRACT FROM AUTHOR]

Modern geotechnical monitoring is based on a variety of surface-based and integrated sensors. This article discusses the potential but also the limitations of total stations and laser scanners in monitoring of civil infrastructure and natural phenomena. We report about our experiences gained in long-term monitoring projects and discuss the impact of the setup location, the signal travel path, and the target. Although modern instruments are capable of measurements with accuracies of a few millimetres or better, neglecting error sources like temperature dependence of the tilt sensor, orientation of the used prism, obstructions and reflections of the measurement beam, and atmospheric refraction can easily cause errors of several millimetres or even centimetres. [ABSTRACT FROM AUTHOR]

Sensor technologies have been innovated and enhanced rapidly for highly automated vehicle and advanced driver assistance systems (ADAS) in automotive industry; however, in order to adopt sensors into mass production vehicle in near future, various requirements should be satisfied such as cost, durability, and maintainance without any loss of overall performance of the sensors. In this sense, a 3D flash lidar is one of primising range sensors because of no moving parts, compact package, and precise measure for distance by using a laser. In spite of the several advantages, the 3D flash lidar is not commonly used in automotive industry because it is quite expensive for adoption and it is manufactured with only general purpose currently; therefore, the cost reduction and optimal design to satisfy various purposes of ADAS or autonomous driving should be accomplished. In this paper, we propose a novel approach for design factor optimization of the 3D flash lidar based on a geometrical model by using structural similarity between the 3D flash lidar and 2D digital camera. In particular, focal length and area of a receiver (focal plane array and read-out integrated circuit) which directly affect on sensor performance (field of view and maximum detection range) are optimized as the design factors. From the optimization results in simulation, we show that optimal design factors according to various purposes required in ADAS could be easily determined and the sensor performances could be evaluated before manufacturing. It will reduce temporal and economic burdens for design and manufacturing in development process. [ABSTRACT FROM AUTHOR]

In the procedures to minimize diachronic landslides, data on their temporal evolution and destructive capacities are necessary. For that purpose, remote-detection techniques proved to be highly useful for quantifying the ongoing change in the relief, as well as in comparisons between digital terrain models achieved by Light Detection and Ranging. The methodology presented in this paper includes the supervised merging and comparison of sequential scans, acquired within nearly annual intervals from an irregular terrain, which improves the quality of the results highlighting ground changes. This approach is based on the processing of digital terrain models from point clouds acquired by Terrestrial Laser Scanning to quantify and interpret the landslide displacements. In parallel, it is supported by Global Navigation Satellite Systems, the use of artificial targets and a refined data processing to minimize the uncertainty and improve the precision of the results. This is applied to a large translational slide affecting phyllite rocks in a IV-V degree of weathering settled on the southern slope of Sierra Nevada (south-eastern Spain). During the monitoring period (2008-2010), the slide remained inactive until 2009, followed by a reactivation with displacements in the range −1.80 to 1.20 m along the period 2009-2010, where negative values are downwards from the reference model (2009). The accumulated relative standard deviation between data sets was on the order of 7.5 cm, whereas the threshold to determine a terrain displacement (also avoiding changes due to erosion-accumulation processes) was of 10 cm. When applying this methodology to Airborne Laser Scanning datasets for the years 2008 and 2010, covering zones hidden to the line of sight of the terrestrial technique, a reactivation with similar deformation pattern was found useful to validate the findings, although the detail of changes and quantitative results did not match exactly due to the different accuracy and resolution of both techniques. The reactivation of the slide coincided with a period of intense rains, pointing to this as the triggering factor, with a precipitation threshold of roughly 1000 mm in a period of 4 months, only reached on one occasion throughout in the historical record. [ABSTRACT FROM AUTHOR]

This paper discusses two different methods for the detection of flatness defects present on the mounting surfaces of oil pans using laser-scanned point clouds. The first method involves registration, which is a widely used method in the field of 3D data inspection: scanned point clouds are registered with CAD data and the iterative closest point (ICP) algorithm is used for further comparison. The second method is our proposed method, a simple yet effective method for measuring the flatness of an oil pan mounting surface. The process is based on the construction of a reference plane on the scanned surface. The oil pan mounting surface is scanned by a 3D laser scanner, obtaining point cloud data that is then further processed to reduce noise. Using this processed data, a reference plane parallel to the direction of the mounting surface is defined at the mean position of the mounting surface. The direction of the reference plane is determined by the normal vector of the mounting surface. Construction of the reference plane is carried out by the singular value decomposition (SVD) technique. The deviation of the surface from the reference plane is measured by calculating the error distance between the points of the surface to the reference plane using the least-squares method. [ABSTRACT FROM AUTHOR]

This paper attempts to evaluate various methods of geometrical discontinuity characterization using point clouds that are generated with three-dimensional terrestrial laser scanning (3DTLS) in a tunnel. The use of 3DTLS to support discontinuity mapping in tunnels enables the acquisition of a large amount of data without limitations in terms of the tunnel position (wall or roof). Thus, the discontinuity orientation, trace length and frequency were statistically analyzed in different regions of the tunnel to determine the most representative data. Different methods of estimating the mean trace length were compared while considering the variations in the rock face orientation in the tunnel, and the unbiased standard deviation of the trace length was evaluated. The frequencies of discontinuity sets were obtained using scanlines, and aspects of window sampling for density (areal frequency) estimates in tunnels are discussed. The mean trace lengths obtained using rectangular sampling windows (considering the relative frequency of the traces) are more suitable for estimates of different rock face orientations, particularly when the orientation of the discontinuity set varies significantly. In this case, measurements of samples from the tunnel roof presented higher values for both frequency and mean trace length estimates, which demonstrates the importance of data acquisition and evaluation in this region. [ABSTRACT FROM AUTHOR]

The paper discusses the contribution given by geomatics to monitoring operations regarding a large landslide. The phenomenon affects an entire hill at the edge of the town of Maierato, southern Italy, which bisected the main access road to the town. In the first year after the main event, several surveying methods have been performed by different institutions, often not coordinated. At the end of 2010, an agreement was stated between the Civil Protection Department and the CAMILab of the University of Calabria, regarding the realization of geological, geotechnical, hydrological, and hydraulic studies and surveys in the Municipality of Maierato. The aim is to set up a model of the evolution of the phenomenon and to obtain the periodic assessment of the residual risk level. For understanding the event deeply, the integration of a number of methods of investigation, both geophysical and geotechnical, with geomatics techniques has been performed. The final goal is to set up an early warning system. The used geomatics techniques are the following: total station (operating continuously), Global Navigation Satellite System (GNSS) surveys, laser scanner, and digital photogrammetry. The total station controls and transmits the position of 20 points continuously. The design of the control network and the data acquired during the first 11 months of monitoring are discussed. GNSS receivers are used in static mode for the reference points. Kinematic and RTK surveys have been made to obtain the cross sections, useful to interpret the geoelectrical tomography correctly. Laser scanner has been used to obtain a 3-D model of the area and to evaluate the volume of the landslide. The first 18 months of continuous monitoring show, on the one hand, an excellent repeatability of the measures, and on the other, they confirm the results obtained by geotechnical investigations (inclinometers, etc.) and surface surveys. [ABSTRACT FROM AUTHOR]

The capability to measure at distance dense cloud of 3D point has improved the relevance of geomatic techniques to support risk assessment analysis related to slope instability. This work focuses on quantitative analyses carried out to evaluate the effects of potential failures in the Vulcano Island (Italy). Terrestrial laser scanning was adopted to reconstruct the geometry of investigated slopes that is required for the implementation of numerical modeling adopted to simulate runout areas. Structural and morphological elements, which influenced past instabilities or may be linked to new events, were identified on surface models based on ground surveying. Terrestrial laser scanning was adopted to generate detailed 3D models of subvertical slopes allowing to characterize the distribution and orientation of the rock discontinuities that affect instability mechanism caused by critical geometry. Methods for obtaining and analyzing 3D topographic data and to implement simulation analyses contributing to hazard and risk assessment are discussed for two case studies (Forgia Vecchia slope and Lentia rock walls). [ABSTRACT FROM AUTHOR]

A detailed analysis of the pre-failure behavior of the 3 December 2013 rockfall (1,012 m) occurred on Puigcercós pilot study area (Catalonia, Spain) is presented. The exact date of failure was obtained based on a photographic monitoring performed every 4 h. The long-term monitoring (2,217 days) of the rock slope carried out by a Terrestrial LiDAR allowed the early detection of both pre-failure deformation and precursory rockfalls preceding the final failure. By means of the analysis of the pre-failure deformation, four different deformed areas were detected and the tertiary creep phase was observed in three of them. An attempt to predict the time to failure was performed using the Fukuzono's () method. Furthermore, the temporal evolution of the precursory rockfalls occurred in those four areas during the progressive failure showed a close resemblance with the exponential pattern of the cumulated displacements at tertiary creep stage. Finally, the study of the meteorological conditions did not show any single triggering factor associated with the final failure. Reversely, the increase in the occurrence of precursory rockfalls on several areas of the slope together with the observed acceleration on the deformation pattern reinforce the role of a progressive degradation of the stability conditions, which ultimately leaded to the 3 December rockfall event. [ABSTRACT FROM AUTHOR]

The development of laser scanning is one of the surveying methods, which able to produce a digital surface in a short period. The good results of digital surface must be followed by specific procedures, for example, interpolation algorithm and filtering methods. The improvement in information technology has influenced the growing development and application of laser scanning technique in order to fulfill the user needs. Laser scanning resolution might have an effect on the results of slope mapping studies. The objective of this paper is to evaluate the results of different laser scanner resolutions in producing a slope map. This study was conducted at Cameron Highlands, Pahang, Malaysia. Two site locations were identified for this study due to the condition of the slope characteristics that provides a more accurate assessment. Topcon GLS1500 is being used for data collection at both sites, and several control points were established using real-time kinematic global positioning system. The storage of point clouds was increased when the resolution value is decreased. The results of laser scanner were analyzed based on different laser scanner resolutions. It can be concluded that laser scanner resolutions do have an effect on slope mapping accuracies. Determination of the appropriate resolution for specific applications can be identified in this study. [ABSTRACT FROM AUTHOR]

We have developed a one-axis on-the-fly system that can continuously process a large area by using a laser scanner. Existing laser processing using scanner systems can be used for precision processing, but have a limitation in the area of processing. To supplement this shortcoming, a step and scanning technique using a stage has been developed. This technique can process a large area in such a way that, after laser processing, the stage moves repetitively; however, this method has a demerit in that processing quality in the part between the scan areas is not even. To solve this problem, there is a method of synchronizing the scanner and the stage. This study developed an on-the-fly system that synchronizes the one-axis stage and the two-axis scanner. Also, in synchronized processing, the velocity of the stage due to the velocity of fabrication is very important. If the velocity of the stage is not proper, the laser processing deviates from the scanner work area. We proposed an algorithm in which, using a cell decomposition method, the velocity of the stage is automatically calculated by compensating for the acceleration/deceleration time occurring in the stage rotation and the reverse rotation due to the velocity of the fabrication. We compared the step and scanning method to the on-the-fly method through a low-frequency experiment and proved that the latter has better precision for the boundary of the scan area; we further analyzed the precision by using a large area marking and an overlapping experiment. In addition, by measuring encoder output signals, a compensation algorithm for the stage acceleration/deceleration time was verified. [ABSTRACT FROM AUTHOR]

We present a long-term spatio-temporal analysis of rock slope evolution using a Terrestrial LiDAR aiming to improve our understanding of the link between pre-failure deformation and the spatial prediction of rockfalls. We monitored the pilot study area located at the Puigcercós cliff (Catalonia, Spain) over a period of 1,705 days and detected the deformation of nine different cliff regions together with a high rockfall activity. An exact match was observed between the progressively deformed areas and the regions recently affected by three of the highest magnitude rockfall events, demonstrating a causal relationship between pre-failure deformation and rockfall occurrence. These findings allowed us to make a forward spatial prediction of future failures, hypothesizing a high probability of failure in the six remaining regions. We observed an exponential acceleration of the deformation close to failure, in accordance with tertiary creep theory. However, the temporal analysis of the deformed areas showed a complex and variable behavior, so no exact prediction of the date of failure can yet be made. Our findings have broadened our understanding of the pre-failure behavior of rockfalls and have clear implications for the future implementation of early warning systems. [ABSTRACT FROM AUTHOR]

Multi-sensor coordinate measuring machines (CMM) have a potential performance advantage over existing CMM systems by offering the accuracy of a touch trigger probe with the speed of a laser scanner. Before these systems can be used, it is important that both random and systematic errors are evaluated within the context of its intended application. At present, the performance of a multi-sensor CMM, particularly of the laser scanner, has not been evaluated within an automotive environment. This study used a full-scale CNC machined physical representation of a sheet metal vehicle body to evaluate the measurement agreement and repeatability of critical surface points using a multi-sensor horizontal dual arm CMM. It was found that there were errors between CMM arms and with regard to part coordinate frame construction when using the different probing systems. However, the most significant effect upon measurement error was the spatial location of the surface feature. Therefore, for each feature on an automotive assembly, measurement agreement and repeatability has to be individually determined to access its acceptability for measurement with a laser scanner to improve CMM utilisation, or whether the accuracy of a touch trigger probe is required. [ABSTRACT FROM AUTHOR]

There is a growing demand for technologies that support capturing of comprehensive and good quality 3D spatial data at a faster rate with low investment and minimal effort, while also causing least disturbance to other activities in the area. Mobile mapping systems (MMS), which are being developed in a few western countries, solve this problem but their import is highly expensive. While the components of a MMS are easily available off-the-shelf at lower cost, the main reason for their high cost is the intellectual property involved in the sensor design, integration, calibration, and the related software. Developing the intellectual property locally can bring down the cost of MMS to a large extent. Keeping this in mind, a MMS has been developed in this research using the locally available sensors. This paper describes the methodology to integrate navigation and mapping sensors including the developed calibration procedures. It further describes the time synchronization technique developed for multi-sensor data fusion and algorithms implemented by software package for data processing. The sensors integrated in the MMS include a standard GPS, IMU and a standard laser scanner. A Kalman filter is implemented to integrate the GPS and IMU data, which provides position and orientation information for the sensors. A simulation software package is also developed to verify, understand and develop the equations used in MMS. Field tests have been performed using the developed MMS and the results are shown for a few cases. Results validate the designed algorithms and indicate the successful development of the MMS, which has potential to be further developed and used in field. Though a number of papers are available on MMS, the thrust of this paper is to present a complete methodology for developing a MMS using locally available sensors. Unlike available papers, this paper outlines all aspects of design, calibration and operation, where each of these aspects is handled in a novel way as demanded by the available sensors. This is particularly useful for individuals or organizations interested in procuring sensor components off-the-shelf and develop their own (low cost) Mobile Mapping system. [ABSTRACT FROM AUTHOR]

For deriving the robust estimation by the EM (expectation maximization) algorithm for a model, which is more general than the linear model, the nonlinear Gauss Helmert (GH) model is chosen. It contains the errors-in-variables model as a special case. The nonlinear GH model is difficult to handle because of the linearization and the Gauss Newton iterations. Approximate values for the observations have to be introduced for the linearization. Robust estimates by the EM algorithm based on the variance-inflation model and the mean-shift model have been derived for the linear model in case of homoscedasticity. To derive these two EM algorithms for the GH model, different variances are introduced for the observations and the expectations of the measurements defined by the linear model are replaced by the ones of the GH model. The two robust methods are applied to fit by the GH model a polynomial surface of second degree to the measured three-dimensional coordinates of a laser scanner. This results in detecting more outliers than by the linear model. [ABSTRACT FROM AUTHOR]

In this paper, a flexible high-precision calibration method suitable for industrial field was proposed. The complexity of the coordinate transformation was simplified by choosing the camera coordinate system as the unified reference coordinate system. A flexible planar calibration pattern was introduced to the calibration process, which can be arbitrarily placed and from which the known feature points can be extracted to construct other unknown feature points. With the known intrinsic parameters, the laser projector plane equation was fitted by the multi-noncollinear points, which were acquired through the principle of triangulation and the projective invariance of cross ratio. With this method, the strict alignment and multiple times of coordinate transformation can be avoided. Experimental results showed that the arithmetic mean of the root mean square (RMS) error of distance was 0.000 7 mm. [ABSTRACT FROM AUTHOR]

The study of desiccation cracks in soils has been a subject of increasing attention in recent research. This paper presents the use of a 2D profile laser that is coupled with a motion controller (that allows scanning the overall surface of a drying soil) and electronic balance (to measure the water loss). The aim is to accurately track the three most relevant variables associated with the behavior of soils during desiccation: volume change, water loss and evolving crack network’s morphology. The paper presents the methodology to obtain a digital model of the soil using the experimental setup described above. The main results of a natural soil subjected to drying are presented and discussed, including evolution of cracks aperture; evolution of cracks depth, surface contour levels (at different times); and evolution of volume change. It is shown that the proposed methodology provides very useful information for studying the behavior of soils subjected to desiccation. [ABSTRACT FROM AUTHOR]

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This paper introduces a model based detection approach for typical structures in the agricultural environment. In contrast to other existing approaches in this area it exclusively relies on distance data information generated by a laser scanner which makes the detection robust against varying illumination. Additionally, the method was designed to be easily adaptable to different agricultural structures as well as to minimize computation power. To test the performance and the capabilities of the presented approach a prototypical baling assistance system was implemented where a tractor had to follow a straw windrow while the implement created round bales. [ABSTRACT FROM AUTHOR]