In areas with border extension (localities, mining areas, hydrotechnics, etc.) it is advisable to establish the positions of the points in a local system, the methods used being simpler and the ...results more precise. However, it is necessary to transcalculate the coordinates from the local system to the national projection system. A transcalculation method is assumed to ensure efficiency and accuracy.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Light Detection and Ranging (LiDAR) and Structure from Motion (SfM) provide large amounts of digital data from which virtual outcrops can be created. The accuracy of these surface reconstructions is ...critical for quantitative structural analysis. Assessment of LiDAR and SfM methodologies suggest that SfM results are comparable to high data-density LiDAR on individual surfaces. The effect of chosen acquisition technique on the full outcrop and the efficacy on its virtual form for quantitative structural analysis and prediction beyond single bedding surfaces, however, is less certain. Here, we compare the accuracy of digital virtual outcrop analysis with traditional field data, for structural measurements and along-strike prediction of fold geometry from Stackpole syncline. In this case, the SfM virtual outcrop, derived from UAV imagery, yields better along-strike predictions and a more reliable geological model, in spite of lower accuracy surface reconstructions than LiDAR. This outcome is attributed to greater coverage by UAV and reliable reconstruction of a greater number of bedding planes than terrestrial LiDAR, which suffers from the effects of occlusion. Irrespective of the chosen acquisition technique, we find that workflows must incorporate careful survey planning, data processing and quality checking of derived data if virtual outcrops are to be used for robust structural analysis and along-strike prediction.
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•3 virtual outcrops of the same field structure compared for accuracy and coverage.•Derived from: terrestrial LiDAR, terrestrial images & UAV images.•Fidelity of virtual bedding surfaces tested against compass-clinometer measurements.•LiDAR-derived reconstructions of greatest accuracy, but lowest outcrop coverage.•Synoptic UAV positions sample entire outcrop, improving geological predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
OSXStereonet is a Macintosh application to plot spherical data (lines, planes and small circles) in 2D, equal angle or equal area stereonets of any view orientation, or in 3D. The program can also ...operate on the data calculating angles and intersections between lines or planes, lines (poles) from planes and vice versa, or performing rotations and statistical analyses (cylindrical or conical best fit, mean vectors and contouring) of the data. The stereonet and most of the program's methods are based on linear algebra. We illustrate the functionality of the program as well as its close relation to linear algebra concepts such as transformations through several examples including down plunge projections, map calculations, stress orientations and paleomagnetic reversal tests.
► A Macintosh program to visualize and operate on spherical data in 2D and 3D. ► The mathematics of the stereonet and its operations is described. ► Vectors and even second order tensors problems can be solved with stereonets.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The routine application of remote surveying techniques which can quickly acquire 3D digital data with high resolution, in particular digital photogrammetry, light detection and ranging (LiDAR) and ...unmanned aerial vehicle (UAV) for rock mass characterization has rapidly grown over the past decade. In this paper, a new method for automatic identification and interpretation of rock mass discontinuities, clustering of discontinuity sets and characterization of discontinuity orientation, persistence and spacing using 3D point clouds, is presented. The proposed method is based on a four-stage procedure consisting of: (1) normal vector calculation using the iterative reweighted plane fitting (IRPF) method, (2) discontinuity sets clustering by fast search and find of density peaks (CFSFDP) algorithm, and Fisher’s K value iterative calculation to eliminate noise points, (3) discontinuity segmentation using density-ratio based method, and discontinuity plane fitting using the random sample consensus (RANSAC) algorithm, (4) persistence and spacing calculation using the theory of analytic geometry. The method is applied to two case studies (i.e. rock slopes) and compared with the results from previous studies and from manual survey. It is concluded that the proposed method is reliable and yields a great accuracy for automatic identification of discontinuities in rock masses.
•An automatic method using machine learning algorithms for discontinuity identification and extraction is proposed.•Several discontinuity parameters, namely number of sets, orientation, spacing and trace length can be obtained.•Discontinuity location, best fitting plane, and 3D trace mapping can also be performed.•This method is applied for two real cases and produces reliable and accuracy results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, two types of stress induced hexagonal close packed structure to face centered cubic structure transformation were observed in cold-rolled pure titanium. The corresponding transformation ...mechanisms were revealed by high resolution transmission electron microscopy. By using stereographic projections and selected area electron diffraction simulations, the three dimensional orientation relationships for the two types of phase transformation were deduced for the first time. The deduced orientation relationships were also verified by high resolution transmission electron microscopy observations, and the dark side of the basal-type face centered cubic phase was revealed at the atomic scale.
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•Two types of hcp to fcc transformations were characterized at atomic scale by HRTEM.•3-D orientation relationships for hcp to fcc transformation were investigated in Ti.•The deduced 3-D orientation relationships were verified by HRTEM observations.•A guidance for studying the 3-D morphology of fcc phase in hcp phase was provided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
As part of the Greenland Ice Mapping Project (GIMP) we have produced three geospatial data sets for the entire ice sheet and periphery. These are (1) a complete, 15 m resolution image mosaic, (2) ...ice-covered and ice-free terrain classification masks, also posted to 15 m resolution, and (3) a complete, altimeter-registered digital elevation model posted at 30 m. The image mosaic was created from a combination of Landsat-7 and RADARSAT-1 imagery acquired between 1999 and 2002. Each pixel in the image is stamped with the acquisition date and geo-registration error to facilitate change detection. This mosaic was then used to manually produce complete ice-covered and ice-free land classification masks. Finally, we used satellite altimetry and stereo-photogrammetric digital elevation models (DEMs) to enhance an existing DEM for Greenland, substantially improving resolution and accuracy over the ice margin and periphery.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Powerful methods of paleostress analysis from fault-slip data have been used since the 1970's, and have demonstrated their capacity for reconstructing stress fields with tectonic significance. ...However, in some cases, these methods have been applied to samples that do not fulfill basic requirements, or developed on the basis of unsound conceptual models. Most methods of fault-slip are based on the Wallace-Bott principle (dynamic paradigm), while others invoke the necessity of remaining within the alternative kinematic paradigm, therefore inferring only finite strain or strain rate axes. The scientific community shares neither standard procedures for applying these methods, nor standard parameters for assessing the quality of results. This indicates that paleostress analysis has not attained maturity. It is necessary to see back to the conceptual and methological bases, following accurate procedures of data collection, using additional field observations, and critically assessing the results within the tectonic setting. Spatial and temporal heterogeneity of stress fields over all scales makes the mean stress tensor obtained from site analysis just an abstract notion, though indispensable for understanding lithosphere dynamics.
•The scientific community shares neither standard procedures, nor quality criteria of stress inversion.•The dynamic paradigm can be reconciled with the kinematic paradigm of fault-slip analysis.•The inferred mean stress tensors generally have tectonic significance.•Spatial and temporal heterogeneity of stress fields should be kept in mind.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Oxide glasses with a network structure are omnipresent in daily life. Often, they are regarded as isotropic materials; however, structural anisotropy can be induced through processing in mechanical ...fields and leads to unique materials properties. Unfortunately, due to the lack of local, atomic-scale analysis methods, the microscopic mechanisms leading to anisotropy remained elusive. Using novel analysis methods on glasses generated by molecular dynamics simulations, this paper provides a microscopic understanding of topological anisotropy in silica (SiO2) glass under mechanical loads. The anisotropy observed in silica glass originates from a preferred orientation of SiO4 tetrahedra at both short- and medium-range levels that can be controlled via the mode of mechanical loading. The findings elucidate the relation between the deformation protocol and the resulting anisotropic structure of the silica network (involving both persistent and transient effects), and thus provide important insight for the design of oxide glasses with tailored materials properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Searching for an efficient and reliable method to reduce manual intervention and subjective parameter selection during the discontinuity characterization process of rock tunnel faces is an important ...task. This paper presents a new method for semi-automatic discontinuity characterization in rock tunnel faces using 3D point cloud data, which consists of the following five procedures: (1) regions of interest selection, (2) octree-based local curvature calculation, (3) automatic discontinuity sets classification, (4) cluster analysis for point cloud data, and (5) visualization of classified discontinuity sets. To evaluate the performance of the proposed method, the point cloud data of three rock tunnel faces are collected and established using a photogrammetry-based scheme. Experiments are carried out to identify the optimized parameter values (point cloud density, plane radius, and discontinuity set number) for discontinuity characterization in a typical rock tunnel face. Using the optimized parameter values, the proposed method showed excellent performance and the statistical discontinuity orientation data were in good agreement with those obtained through in situ measurements. In comparison with the other two state-of-the-art methods (the Discontinuity Set Extractor (DSE) method and the qfacet fast marching (qfacet FM) method), the proposed method demonstrates improved processing efficiency and reasonable accuracy for discontinuity characterization using 3D point clouds. Overall, this study provides a step forward towards automatic 3D discontinuity characterization and visualization in the field for rock tunnel engineers.
•A novel method is proposed for semi-automatic discontinuity characterization.•Both manual intervention and subjective parameter selection are reduced.•Comparisons with two state-of-the-art methods are conducted and evaluated.•Promising processing efficiency and reasonable accuracy are achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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