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Batakanwa, Nicholas, and Tomasz Lipecki. "The use of video camera to create metric 3D model of engineering objects." Geoinformatica Polonica 19 (2020): 59–71. http://dx.doi.org/10.4467/21995923gp.20.006.12827.
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The article presents the possibilities of using a video camera to create a 3D metric model of engineering objects using Agisoft and CloudCompare software. Traditional photogrammetry technique does not always match up with production urgency needed by the market. Complexity is seen when used in huge objects leading to rise of cost, time and tediousness of the work. The use of Video Camera technique here termed as videogrammetry technique is comparable to taking pictures, however, it allows to speed up the process of obtaining data, which in many cases is a key element in anyb any project or research. The analysis of the quality of 3D modelling of the three filmed objects was performed, which allowed the authors to refine the procedure for acquiring images for spatial analyses. The applied technique of “videogrammetry” is comparable to taking pictures, but allows the data acquisition process to speed up, which in many cases is a key element in field research. 3D objects videos from no-metric camera were processed by Agisoft Metashape. To be able to assess the accuracy of the videogrammetry data, a well-established Laser scanner technique’s data was used for comparison. The laser scanner data were pre-processed in Autodesk Recap. Manual registration was performed utilizing 14 points from the three scans. The two 3D models were exported to CloudCompare software for comparison and further analysis. An analysis of the quality of 3D modelling of the three objects filmed was performed, which allowed refining the procedure for obtaining images for spatial analysis. The article presents the possibilities of using a non-metric mobile phone video camera “videogrammetry” to create a metric 3D model of engineering objects using Agisoft and CloudCompare software. In CloudCompare a registration, cloud to cloud (C2C) and profile to profile analysis was performed to determine the uncertainty of the 3D model produced from videogrammetry data determined as distance of separation between the two models. Results show average distance of separation between laser scanner and videogrammetry derived 3D model point cloud to be 34cm, the average profile separation was 25 cm in XY plane and 1.9 cm in Z-plane. Using Cloud to Cloud PCV the average difference of 84 cm was determined.
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Dewez, T. J. B., D. Girardeau-Montaut, C. Allanic, and J. Rohmer. "FACETS : A CLOUDCOMPARE PLUGIN TO EXTRACT GEOLOGICAL PLANES FROM UNSTRUCTURED 3D POINT CLOUDS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 16, 2016): 799–804. http://dx.doi.org/10.5194/isprsarchives-xli-b5-799-2016.
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Geological planar facets (stratification, fault, joint…) are key features to unravel the tectonic history of rock outcrop or appreciate the stability of a hazardous rock cliff. Measuring their spatial attitude (dip and strike) is generally performed by hand with a compass/clinometer, which is time consuming, requires some degree of censoring (i.e. refusing to measure some features judged unimportant at the time), is not always possible for fractures higher up on the outcrop and is somewhat hazardous. 3D virtual geological outcrop hold the potential to alleviate these issues. Efficiently segmenting massive 3D point clouds into individual planar facets, inside a convenient software environment was lacking. FACETS is a dedicated plugin within CloudCompare v2.6.2 (<a href="http://cloudcompare.org/"target="_blank">http://cloudcompare.org/</a> ) implemented to perform planar facet extraction, calculate their dip and dip direction (i.e. azimuth of steepest decent) and report the extracted data in interactive stereograms. Two algorithms perform the segmentation: Kd-Tree and Fast Marching. Both divide the point cloud into sub-cells, then compute elementary planar objects and aggregate them progressively according to a planeity threshold into polygons. The boundaries of the polygons are adjusted around segmented points with a tension parameter, and the facet polygons can be exported as 3D polygon shapefiles towards third party GIS software or simply as ASCII comma separated files. One of the great features of FACETS is the capability to explore planar objects but also 3D points with normals with the stereogram tool. Poles can be readily displayed, queried and manually segmented interactively. The plugin blends seamlessly into CloudCompare to leverage all its other 3D point cloud manipulation features. A demonstration of the tool is presented to illustrate these different features. While designed for geological applications, FACETS could be more widely applied to any planar objects.
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Nagendran, Sharan Kumar, Mohd Ashraf Mohamad Ismail, and Yan Tung Wen. "Photogrammetry approach on geological plane extraction using CloudCompare FACET plugin and scanline survey." Bulletin of the Geological Society of Malaysia 68 (December 31, 2019): 151–58. http://dx.doi.org/10.7186/bgsm68201916.
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Dewez, T. J. B., D. Girardeau-Montaut, C. Allanic, and J. Rohmer. "FACETS : A CLOUDCOMPARE PLUGIN TO EXTRACT GEOLOGICAL PLANES FROM UNSTRUCTURED 3D POINT CLOUDS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 16, 2016): 799–804. http://dx.doi.org/10.5194/isprs-archives-xli-b5-799-2016.
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Geological planar facets (stratification, fault, joint…) are key features to unravel the tectonic history of rock outcrop or appreciate the stability of a hazardous rock cliff. Measuring their spatial attitude (dip and strike) is generally performed by hand with a compass/clinometer, which is time consuming, requires some degree of censoring (i.e. refusing to measure some features judged unimportant at the time), is not always possible for fractures higher up on the outcrop and is somewhat hazardous. 3D virtual geological outcrop hold the potential to alleviate these issues. Efficiently segmenting massive 3D point clouds into individual planar facets, inside a convenient software environment was lacking. FACETS is a dedicated plugin within CloudCompare v2.6.2 (<a href="http://cloudcompare.org/"target="_blank">http://cloudcompare.org/</a> ) implemented to perform planar facet extraction, calculate their dip and dip direction (i.e. azimuth of steepest decent) and report the extracted data in interactive stereograms. Two algorithms perform the segmentation: Kd-Tree and Fast Marching. Both divide the point cloud into sub-cells, then compute elementary planar objects and aggregate them progressively according to a planeity threshold into polygons. The boundaries of the polygons are adjusted around segmented points with a tension parameter, and the facet polygons can be exported as 3D polygon shapefiles towards third party GIS software or simply as ASCII comma separated files. One of the great features of FACETS is the capability to explore planar objects but also 3D points with normals with the stereogram tool. Poles can be readily displayed, queried and manually segmented interactively. The plugin blends seamlessly into CloudCompare to leverage all its other 3D point cloud manipulation features. A demonstration of the tool is presented to illustrate these different features. While designed for geological applications, FACETS could be more widely applied to any planar objects.
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Rajendra, Y. D., S. C. Mehrotra, K. V. Kale, R. R. Manza, R. K. Dhumal, A. D. Nagne, and A. D. Vibhute. "Evaluation of Partially Overlapping 3D Point Cloud's Registration by using ICP variant and CloudCompare." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 28, 2014): 891–97. http://dx.doi.org/10.5194/isprsarchives-xl-8-891-2014.
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Terrestrial Laser Scanners (TLS) are used to get dense point samples of large object’s surface. TLS is new and efficient method to digitize large object or scene. The collected point samples come into different formats and coordinates. Different scans are required to scan large object such as heritage site. Point cloud registration is considered as important task to bring different scans into whole 3D model in one coordinate system. Point clouds can be registered by using one of the three ways or combination of them, Target based, feature extraction, point cloud based. For the present study we have gone through Point Cloud Based registration approach. We have collected partially overlapped 3D Point Cloud data of Department of Computer Science & IT (DCSIT) building located in Dr. Babasaheb Ambedkar Marathwada University, Aurangabad. To get the complete point cloud information of the building we have taken 12 scans, 4 scans for exterior and 8 scans for interior façade data collection. There are various algorithms available in literature, but Iterative Closest Point (ICP) is most dominant algorithms. The various researchers have developed variants of ICP for better registration process. The ICP point cloud registration algorithm is based on the search of pairs of nearest points in a two adjacent scans and calculates the transformation parameters between them, it provides advantage that no artificial target is required for registration process. We studied and implemented three variants Brute Force, KDTree, Partial Matching of ICP algorithm in MATLAB. The result shows that the implemented version of ICP algorithm with its variants gives better result with speed and accuracy of registration as compared with CloudCompare Open Source software.
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Nagle-McNaughton, Timothy, and Rónadh Cox. "Measuring Change Using Quantitative Differencing of Repeat Structure-From-Motion Photogrammetry: The Effect of Storms on Coastal Boulder Deposits." Remote Sensing 12, no. 1 (December 20, 2019): 42. http://dx.doi.org/10.3390/rs12010042.
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Repeat photogrammetry is increasingly the go-too tool for long-term geomorphic monitoring, but quantifying the differences between structure-from-motion (SfM) models is a developing field. Volumetric differencing software (such as the open-source package CloudCompare) provides an efficient mechanism for quantifying change in landscapes. In this case study, we apply this methodology to coastal boulder deposits on Inishmore, Ireland. Storm waves are known to move these rocks, but boulder transportation and evolution of the deposits are not well documented. We used two disparate SfM data sets for this analysis. The first model was built from imagery captured in 2015 using a GoPro Hero 3+ camera (fisheye lens) and the second used 2017 imagery from a DJI FC300X camera (standard digital single-lens reflex (DSLR) camera); and we used CloudCompare to measure the differences between them. This study produced two noteworthy findings: First, volumetric differencing reveals that short-term changes in boulder deposits can be larger than expected, and that frequent monitoring can reveal not only the scale but the complexities of boulder transport in this setting. This is a valuable addition to our growing understanding of coastal boulder deposits. Second, SfM models generated by different imaging hardware can be successfully compared at sub-decimeter resolution, even when one of the camera systems has substantial lens distortion. This means that older image sets, which might not otherwise be considered of appropriate quality for co-analysis with more recent data, should not be ignored as data sources in long-term monitoring studies.
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Chun Yee, Glen Lim, Yeo Joon Hock, Tsuyoshi Nishiwaki, Kenta Moriyasu, and Kenichi Harano. "Abrasion wear analysis in running shoes using a gridded methodology with CIE-L-a-b colour identification." Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology 233, no. 3 (February 14, 2018): 333–41. http://dx.doi.org/10.1177/1754337118755270.
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Wear identification and projection have eluded shoe manufacturers due to the myriad of factors that affect the abrasion wear of shoes. Using a gridded three-dimensional cloud comparison in CloudCompare software, abrasion wear thickness of shoes was identified using the CIE-L-a-b colour system that is interpolated with the physical formula representation of colours. After obtaining the thickness lost, other wear factors like the material properties of the shoe sole, the runners’ personal profile and the running schedule were combined for wear projection. The methodological process from a non-destructive wear detection to wear projection allows shoe manufacturers to reduce the iterations of wear testing while maximizing the entire analysis of shoe wear. Shoe samples were kindly sponsored by ASICS Institute of Sport Science.
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Tung, Wen Yan, Sharan Kumar Nagendran, and Mohd Ashraf Mohamad Ismail. "3D rock slope data acquisition by photogrammetry approach and extraction of geological planes using FACET plugin in CloudCompare." IOP Conference Series: Earth and Environmental Science 169 (July 31, 2018): 012051. http://dx.doi.org/10.1088/1755-1315/169/1/012051.
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Fuentes Porto, Alba, Elisa María Díaz-González, Manuel Drago Díaz-Alemán, and Esteban Manuel Amador-García. "Proceso de registro y seguimiento de daños morfológicos en metal arqueológico mediante documentación 3D." Ge-conservacion 19, no. 1 (June 16, 2021): 309–19. http://dx.doi.org/10.37558/gec.v19i1.1002.
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Gracias a la revolución tecnológica que vive el campo de la documentación del patrimonio vemos cómo los registros 3D se consolidan como recurso documental y se extienden con infinidad de propósitos, entre ellos los estudios morfométricos. Con la intención de contribuir en este campo, proponemos un método encaminado a la detección y cuantificación de cambios formales en bienes de naturaleza metálica, un tipo de material susceptible de sufrir daños físicos en un corto período de tiempo. La puesta en práctica de dicha metodología se ejemplifica a través del estudio efectuado sobre un casco de hierro del s. XVI, conservado en un avanzado estado de mineralización. Fue registrado antes y después de un préstamo temporal apoyándonos en dos sistemas de gran difusión en el campo de la digitalización 3D: el escaneado por luz estructurada y la fotogrametría. Finalmente, se compararon sus registros mediante la herramienta de análisis de datos 3D CloudCompare para detectar sus posibles diferencias.
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Nulty, Adam B. "A Comparison of Full Arch Trueness and Precision of Nine Intra-Oral Digital Scanners and Four Lab Digital Scanners." Dentistry Journal 9, no. 7 (June 23, 2021): 75. http://dx.doi.org/10.3390/dj9070075.
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(1) Background: The purpose of this study is to evaluate the full arch scan accuracy (precision and trueness) of nine digital intra-oral scanners and four lab scanners. Previous studies have compared the accuracy of some intra-oral scanners, but as this is a field of quickly developing technologies, a more up-to-date study was needed to assess the capabilities of currently available models. (2) Methods: The present in vitro study compared nine different intra-oral scanners (Omnicam 4.6; Omnicam 5.1; Primescan; CS 3600; Trios 3; Trios 4; Runyes; i500; and DL206) as well as four lab light scanners (Einscan SE; 300e; E2; and Ineos X5) to investigate the accuracy of each scanner by examining the overall trueness and precision. Ten aligned and cut scans from each of the intra-oral and lab scanners in the in vitro study were brought into CloudCompare. A comparison was made with the master STL using the CloudCompare 3D analysis best-fit algorithm. The results were recorded along with individual standard deviation and a colorimetric map of the deviation across the surface of the STL mesh; a comparison was made to the master STL, quantified at specific points. (3) Results: In the present study, the Primescan had the best overall trueness (17.3 ± 4.9), followed by (in order of increasing deviation) the Trios 4 (20.8 ± 6.2), i500 (25.2 ± 7.3), CS3600 (26.9 ± 15.9), Trios 3 (27.7 ± 6.8), Runyes (47.2 ± 5.4), Omnicam 5.1 (55.1 ± 9.5), Omnicam 4.6 (57.5 ± 3.2), and Launca DL206 (58.5 ± 22.0). Regarding the lab light scanners, the Ineos X5 had the best overall trueness with (0.0 ± 1.9), followed by (in order of increasing deviation) the 3Shape E2 (3.6 ± 2.2), Up3D 300E (12.8 ± 2.7), and Einscan SE (14.9 ± 9.5). (4) Conclusions: This study confirms that all current generations of intra-oral digital scanners can capture a reliable, reproducible full arch scan in dentate patients. Out of the intra-oral scanners tested, no scanner produced results significantly similar in trueness to the Ineos X5. However, the Primescan was the only one to be statistically of a similar level of trueness to the 3Shape E2 lab scanner. All scanners in the study had mean trueness of under 60-micron deviation. While this study can compare the scanning accuracy of this sample in a dentate arch, the scanning of a fully edentulous arch is more challenging. The accuracy of these scanners in edentulous cases should be examined in further studies.
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Cosso, T., I. Ferrando, and A. Orlando. "Surveying and mapping a cave using 3d laser scanner: the open challenge with free and open source software." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-5 (June 6, 2014): 181–86. http://dx.doi.org/10.5194/isprsarchives-xl-5-181-2014.
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The present work is part of a series of activities involving different skills, in order to explore and document in detail one of the most visited caves in Liguria Region. In this context, in addition to speleologists, geologists, videographers, the geomatic expertise has also been involved to carry out a laser scanner survey, in order to produce a three-dimensional model of the two more easily accessible rooms of the cave.<br><br> The survey was carried out using <i>Z+F IMAGER® 5010</i> instrument and the post processing operations related to registration of point clouds have been made with <i>Z+F LaserControl®</i>.<br><br> Subsequently, two different free and open source software were used: <i>MeshLab</i>, to merge the point clouds and to obtain the final mesh, and <i>CloudCompare</i>, to make filtering on the previous results and to extract sections.
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He, Xiaoying, Zeqing Yu, John M. Kemeny, Ann Youberg, and Yunkun Wang. "Change Detection and Feature Extraction of Debris-Flow Initiation by Rock-Slope Failure Using Point Cloud Processing." Advances in Civil Engineering 2021 (January 11, 2021): 1–11. http://dx.doi.org/10.1155/2021/6659996.
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Our understanding of debris-flow initiation by slope failure is restricted by the challenge of acquiring accurate geomorphic features of debris flows and the structural setting of the rock mass in the remote mountainous terrain. Point cloud data of debris flows in Sabino Canyon, Tucson, Arizona, July 2006, with initiation by joint-controlled rock slope were obtained using multitemporal LiDAR scanning. Topographic changes were detected by comparing historical LiDAR scanning data of this area since 2005 by adopting open-source CloudCompare software. The results showed persistent scour and erosion in the debris flows after 2006. Point cloud data of joint-controlled rock in the initiation zone were generated by the means of photogrammetry using Pix4D software. The joint planes, the dip direction and the dip value of the joint plane, the joint spacing, and the joint roughness were therefore acquired by point cloud processing. Our study contributes a foundation for analyzing the relationship between the rock features, the generation of slope failure, and the initiation of debris flows.
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Pesántez, P. C. "LANDSLIDE STUDY USING TERRESTRIAL LASER SCANNER (LiDAR) ANALYSIS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2020 (August 21, 2020): 1251–56. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2020-1251-2020.
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Abstract. In Reina del Cisne (Cuenca-Ecuador) a dynamic sliding process was created due to a cut that was applied at the beginning of the year 2018 to the hillside without technical considerations for the construction of an access road to a house in the sector. From May 2018 to January 2019, period analyzed in this work, the landslide has caused total structural damage (dwellings near the hillside) or partial (houses away from the hillside) and the total collapse of the path that caused the landslide. The field visits from the month of May 2018 and the comparison with CloudCompare of the clouds of points obtained with terrestrial laser scanner (LiDAR) between the months of May 2018 and January 2019 (house) and December 2018 and January 2019 (profiles) have highlighted the high activity of this gliding. It has been analyzed three-dimensionally several profiles along the landslide, in addition to an affected house, where they have experienced phenomena such as: sinking and tilting to slope down with values from 3 cm to 30 cm (profiles) in 30 days to 2.28 m (house) in 230 days.
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Teo, Tee-Ann, Peter Tian-Yuan Shih, Sz-Cheng Yu, and Fuan Tsai. "THE USE OF UAS FOR RAPID 3D MAPPING IN GEOMATICS EDUCATION." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B6 (June 17, 2016): 95–100. http://dx.doi.org/10.5194/isprsarchives-xli-b6-95-2016.
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With the development of technology, UAS is an advance technology to support rapid mapping for disaster response. The aim of this study is to develop educational modules for UAS data processing in rapid 3D mapping. The designed modules for this study are focused on UAV data processing from available freeware or trial software for education purpose. The key modules include orientation modelling, 3D point clouds generation, image georeferencing and visualization. The orientation modelling modules adopts VisualSFM to determine the projection matrix for each image station. Besides, the approximate ground control points are measured from OpenStreetMap for absolute orientation. The second module uses SURE and the orientation files from previous module for 3D point clouds generation. Then, the ground point selection and digital terrain model generation can be archived by LAStools. The third module stitches individual rectified images into a mosaic image using Microsoft ICE (Image Composite Editor). The last module visualizes and measures the generated dense point clouds in CloudCompare. These comprehensive UAS processing modules allow the students to gain the skills to process and deliver UAS photogrammetric products in rapid 3D mapping. Moreover, they can also apply the photogrammetric products for analysis in practice.
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Scaioni, M., J. Crippa, V. Yordanov, L. Longoni, V. I. Ivanov, and M. Papini. "SOME TOOLS TO SUPPORT TEACHING PHOTOGRAMMETRY FOR SLOPE STABILITY ASSESSMENT AND MONITORING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W4 (March 6, 2018): 453–60. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w4-453-2018.
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<p><strong>Abstract.</strong> This paper describes the use of some tool to help training of photogrammetry for applications in the field of landslide and slope stability assessment and monitoring. These tools have been used in classes of the MSc on Civil Eng. for Risk Mitigation at Politecnico di Milano university, Lecco (Italy). The first tools are hardware facilities. The first one consists of a ‘Landslide Simulator,’ where shallow landslides may be reproduced at small scale. Simulations are also used here for active-learning purpose. In particular, here the use of digital images to obtain multi-temporal information is presented. The second tool is a ‘Rock face 3D Modelling Simulator.’ This is used by students to learn how a photogrammetric block should be designed in order to reconstruct rock slopes using Structure-from-Motion photogrammetry. The last to tools are software packages (CloudCompare and LIME) devoted to point cloud analysis (including change detection/ deformation analysis) and advanced visualization, respectively. The combination of these tools together with datasets from either lab and the real field, has been successfully tested to provide efficient training to students in an active-learning fashion.</p>
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Teo, Tee-Ann, Peter Tian-Yuan Shih, Sz-Cheng Yu, and Fuan Tsai. "THE USE OF UAS FOR RAPID 3D MAPPING IN GEOMATICS EDUCATION." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B6 (June 17, 2016): 95–100. http://dx.doi.org/10.5194/isprs-archives-xli-b6-95-2016.
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With the development of technology, UAS is an advance technology to support rapid mapping for disaster response. The aim of this study is to develop educational modules for UAS data processing in rapid 3D mapping. The designed modules for this study are focused on UAV data processing from available freeware or trial software for education purpose. The key modules include orientation modelling, 3D point clouds generation, image georeferencing and visualization. The orientation modelling modules adopts VisualSFM to determine the projection matrix for each image station. Besides, the approximate ground control points are measured from OpenStreetMap for absolute orientation. The second module uses SURE and the orientation files from previous module for 3D point clouds generation. Then, the ground point selection and digital terrain model generation can be archived by LAStools. The third module stitches individual rectified images into a mosaic image using Microsoft ICE (Image Composite Editor). The last module visualizes and measures the generated dense point clouds in CloudCompare. These comprehensive UAS processing modules allow the students to gain the skills to process and deliver UAS photogrammetric products in rapid 3D mapping. Moreover, they can also apply the photogrammetric products for analysis in practice.
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Samra, Adriana Postiglione Buhrer, Marcos Pomini, Francielly Granville, Adrielly Zavolski, Fabio Brasil de Oliveira, and Ariangelo Hauer Dias. "Three-dimensional printed models versus conventional stone models." Brazilian Journal of Oral Sciences 19 (October 7, 2020): e209937. http://dx.doi.org/10.20396/bjos.v19i0.8659937.
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Aim: To compare the accuracy (trueness and precision)of cost-accessible three-dimensional (3D) printed models.Methods: A maxillary typodont (MM) was scanned andprinted 10 times in polylactic acid, resulting in 10 digitalmodels (DMs). Polyvinylsiloxane impressions were made toobtain 10 conventional stone models (SMs). All models werescanned and imported to CloudCompare software. The totalarea and three locations of interest were evaluated (zenith toincisal [Z-I], canine to canine [C-C], and first molar to canine[1M-C] distances). Total area evaluations were performed byaligning the MM and experimental models using the best-fitalgorithm and were compared using the Haussdorf distance.The distances between points of interest were measured usingthe point-picking tool at the same 3D coordinates. The meanvolumetric deviations were considered for trueness analysis.Precision was set as the standard deviation. Statisticaldifferences were evaluated using the Student’s t-test. Results:Total area volumetric comparisons showed that DMs showedsuperior trueness and precision (-0.02 ± 0.03) compared tothe SMs (0.37 ± 0.29) (P < 0.001). No differences between themodels were observed for Z-I (P = .155); however, SMs showedfewer deviations for C-C (P = .035) and 1M-C (P = .001) thanDMs. Conclusions: The DMs presented superior trueness andprecision for total area compared to the SMs; however, the SMswere more accurate when points of interest were evaluated.
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Cechelero, Eduarda Bianchini, Mariá Cortina Bellan, and Maurício André Bisi. "Análise comparativa de técnicas de escaneamento digital: estudo in vitro." ARCHIVES OF HEALTH INVESTIGATION 10, no. 2 (October 22, 2020): 248–54. http://dx.doi.org/10.21270/archi.v10i2.4868.
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Objetivos: O presente estudo tem como objetivo avaliar e comparar a técnica recomendada pelo fabricante e uma técnica de variação padrão de dois scanners intraorais em relação a um escaneamento com um scanner de mesa e analisar a possibilidade de alteração dimensional. Materiais e Métodos: Foram confeccionados 5 grupos (n=5), sendo o G=1 com AutoScan-DS-EX sendo fluxo de trabalho automático, G=2 com TRIOS 3 e técnica recomendada pelo fabricante, G=3 com TRIOS 3 e técnica modificada, G=4 com iTero e técnica recomendada pelo fabricante e G=5 com iTero e técnica modificada, e foram submetidos a uma análise qualitativa de cor pelo software CloudCompare. Resultados: Foi presente bastante alteração dimensional entre os Grupos 2 e 3, 4 e 5, pouca alteração dimensional entre os Grupos 1 e 3, 1 e 5, e nenhuma alteração dimensional entre os Grupos 1 e 2, e 1 e 4. Conclusão: Conclui-se que a modificação da técnica recomendada pelo fabricante altera o padrão final do modelo digitalizado principalmente entre os scanners intraorais, sendo que houve pouca alteração quando as técnicas foram comparadas com um scanner de bancada. A qualidade dos escaneamentos se baseia na quantidade de pontos coletados apresentando-se maior nos escaneamentos com scanner de mesa.
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Rahaman, Hafizur, and Erik Champion. "To 3D or Not 3D: Choosing a Photogrammetry Workflow for Cultural Heritage Groups." Heritage 2, no. 3 (July 3, 2019): 1835–51. http://dx.doi.org/10.3390/heritage2030112.
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The 3D reconstruction of real-world heritage objects using either a laser scanner or 3D modelling software is typically expensive and requires a high level of expertise. Image-based 3D modelling software, on the other hand, offers a cheaper alternative, which can handle this task with relative ease. There also exists free and open source (FOSS) software, with the potential to deliver quality data for heritage documentation purposes. However, contemporary academic discourse seldom presents survey-based feature lists or a critical inspection of potential production pipelines, nor typically provides direction and guidance for non-experts who are interested in learning, developing and sharing 3D content on a restricted budget. To address the above issues, a set of FOSS were studied based on their offered features, workflow, 3D processing time and accuracy. Two datasets have been used to compare and evaluate the FOSS applications based on the point clouds they produced. The average deviation to ground truth data produced by a commercial software application (Metashape, formerly called PhotoScan) was used and measured with CloudCompare software. 3D reconstructions generated from FOSS produce promising results, with significant accuracy, and are easy to use. We believe this investigation will help non-expert users to understand the photogrammetry and select the most suitable software for producing image-based 3D models at low cost for visualisation and presentation purposes.
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Gabara, Grzegorz, and Piotr Sawicki. "Multi-Variant Accuracy Evaluation of UAV Imaging Surveys: A Case Study on Investment Area." Sensors 19, no. 23 (November 28, 2019): 5229. http://dx.doi.org/10.3390/s19235229.
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The main focus of the presented study is a multi-variant accuracy assessment of a photogrammetric 2D and 3D data collection, whose accuracy meets the appropriate technical requirements, based on the block of 858 digital images (4.6 cm ground sample distance) acquired by Trimble® UX5 unmanned aircraft system equipped with Sony NEX-5T compact system camera. All 1418 well-defined ground control and check points were a posteriori measured applying Global Navigation Satellite Systems (GNSS) using the real-time network method. High accuracy of photogrammetric products was obtained by the computations performed according to the proposed methodology, which assumes multi-variant images processing and extended error analysis. The detection of blurred images was preprocessed applying Laplacian operator and Fourier transform implemented in Python using the Open Source Computer Vision library. The data collection was performed in Pix4Dmapper suite supported by additional software: in the bundle block adjustment (results verified using RealityCapure and PhotoScan applications), on the digital surface model (CloudCompare), and georeferenced orthomosaic in GeoTIFF format (AutoCAD Civil 3D). The study proved the high accuracy and significant statistical reliability of unmanned aerial vehicle (UAV) imaging 2D and 3D surveys. The accuracy fulfills Polish and US technical requirements of planimetric and vertical accuracy (root mean square error less than or equal to 0.10 m and 0.05 m).
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Rădulescu, V. M., G. M. T. Rădulescu, Sanda Naș, A. T. Rădulescu, M. Bondrea, and Corina M. Rădulescu. "Geoinformatics Technologies for Preservation of Cultural Heritage, Case Study, Rákóczi-Bánffy Castle, Urmeniș, Bistriţa Năsăud County, Romania." Journal of Applied Engineering Sciences 11, no. 1 (May 1, 2021): 41–48. http://dx.doi.org/10.2478/jaes-2021-0006.
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Abstract The paper presents an application of the methodology used in the paper “Synthetic analysis of geoinformatics technologies for cultural heritage conservation, methodological approach”. The creation of the 3D model of the Rákóczi-Bánffy Castle in Urmeniș, Bistrița Năsăud County, was done by applying and integrating Terrestrial Laser Scanning (TLS) technologies and aerial photogrammetry performed with an Unmanned Aerial Vehicle (UAV). Agisoft Photoscan was used to compare the results and then they were compared with the images scanned using CloudCompare software. Thus, following the performance, with the help of the mentioned software, of a series of processing of the point cloud obtained, through the two imaging technologies, the error between the points belonging to the point cloud taken with UAV and the one taken with Laser Scanner was between 1 and 15 mm, the margin of error being acceptable for monuments without complex architectural details, so that the point cloud resulting from UAVs can be used successfully in this activity. The aim of the paper is to elaborate a geomatic methodology with an optimized cost-quality ratio, later replicable in the analysis of the current state of other constructions of the same type, knowing that over 600 castles in Transylvania alone are in a similar state, and such cases can be found in other Central European states as well.
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Son, Keunbada, Wan-Sun Lee, and Kyu-Bok Lee. "Effect of Different Software Programs on the Accuracy of Dental Scanner Using Three-Dimensional Analysis." International Journal of Environmental Research and Public Health 18, no. 16 (August 10, 2021): 8449. http://dx.doi.org/10.3390/ijerph18168449.
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This in vitro study aimed to evaluate the 3D analysis for complete arch, half arch, and tooth preparation region by using four analysis software programs. The CAD reference model (CRM; N = 1 per region) and CAD test models (CTMs; N = 20 per software) of complete arch, half arch, and tooth preparation were obtained by using scanners. For both CRM and CTMs, mesh data other than the same area were deleted. For 3D analysis, four analysis software programs (Geomagic control X, GOM Inspect, Cloudcompare, and Materialise 3-matic) were used in the alignment of CRM and CTMs as well as in the 3D comparison. Root mean square (RMS) was regarded as the result of the 3D comparison. One-way analysis of variance and Tukey honestly significant difference tests were performed for statistical comparison of four analysis software programs (α = 0.05). In half-arch and tooth preparation region, the four analysis software programs showed a significant difference in RMS values (p < 0.001), but in complete-arch region, no significant difference was found among the four software programs (p = 0.139). As the area of the virtual cast for 3D analysis becomes smaller, variable results are obtained depending on the software program used, and the difference in results among software programs are not considered in the 3D analysis for complete-arch region.
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Alessandri, L., V. Baiocchi, S. Del Pizzo, F. Di Ciaccio, M. Onori, M. F. Rolfo, and S. Troisi. "THE FUSION OF EXTERNAL AND INTERNAL 3D PHOTOGRAMMETRIC MODELS AS A TOOL TO INVESTIGATE THE ANCIENT HUMAN/CAVE INTERACTION: THE LA SASSA CASE STUDY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 14, 2020): 1443–50. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-1443-2020.
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Abstract. Caves have been used by humans and animals for several thousand years until present but, at these time scales, their structures can rapidly change due to erosion and concretion processes. For this reason, the availability of precise 3D models improves the data quality and quantity allowing the reconstruction of their ancient appearance, structure and origin. However, caves are usually characterised by lack of light, high percentage of relative humidity, narrow spaces and complex morphology. Thus, quite often the traditional topographic instruments cannot be employed. In the La Sassa cave (Sonnino, Italy) a huge deposit ranging from Pleistocene to the Second World War has been found and stratigraphic evidence suggested that the shape of the cave and its entrance might have been different. In this paper, the fusion of the internal and external 3D photogrammetric models of the La Sassa, made to support the archaeological excavations, is presented, A Nikon camera with a fisheye lens and a smartphone camera have been used to survey the internal part of the cave, while an aerial drone has been employed for the external area. The two models have been georeferenced and scaled using GCPs acquired by a double frequency GNSS (GPS and GLONASS) receiver. A low-resolution DTM derived from a previous aerial laser scanning survey and the 3D models have been elaborated in CloudCompare environment to highlight the complete morphology of the cave and its surroundings.
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Thiele, Samuel T., Lachlan Grose, Anindita Samsu, Steven Micklethwaite, Stefan A. Vollgger, and Alexander R. Cruden. "Rapid, semi-automatic fracture and contact mapping for point clouds, images and geophysical data." Solid Earth 8, no. 6 (December 21, 2017): 1241–53. http://dx.doi.org/10.5194/se-8-1241-2017.
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Abstract. The advent of large digital datasets from unmanned aerial vehicle (UAV) and satellite platforms now challenges our ability to extract information across multiple scales in a timely manner, often meaning that the full value of the data is not realised. Here we adapt a least-cost-path solver and specially tailored cost functions to rapidly interpolate structural features between manually defined control points in point cloud and raster datasets. We implement the method in the geographic information system QGIS and the point cloud and mesh processing software CloudCompare. Using these implementations, the method can be applied to a variety of three-dimensional (3-D) and two-dimensional (2-D) datasets, including high-resolution aerial imagery, digital outcrop models, digital elevation models (DEMs) and geophysical grids. We demonstrate the algorithm with four diverse applications in which we extract (1) joint and contact patterns in high-resolution orthophotographs, (2) fracture patterns in a dense 3-D point cloud, (3) earthquake surface ruptures of the Greendale Fault associated with the Mw7.1 Darfield earthquake (New Zealand) from high-resolution light detection and ranging (lidar) data, and (4) oceanic fracture zones from bathymetric data of the North Atlantic. The approach improves the consistency of the interpretation process while retaining expert guidance and achieves significant improvements (35–65 %) in digitisation time compared to traditional methods. Furthermore, it opens up new possibilities for data synthesis and can quantify the agreement between datasets and an interpretation.
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Castillo, C., M. R. James, M. D. Redel-Macías, R. Pérez, and J. A. Gómez. "SF3M software: 3-D photo-reconstruction for non-expert users and its application to a gully network." SOIL 1, no. 2 (August 27, 2015): 583–94. http://dx.doi.org/10.5194/soil-1-583-2015.
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Abstract. Three-dimensional photo-reconstruction (PR) techniques have been successfully used to produce high-resolution surface models for different applications and over different spatial scales. However, innovative approaches are required to overcome some limitations that this technique may present for field image acquisition in challenging scene geometries. Here, we evaluate SF3M, a new graphical user interface for implementing a complete PR workflow based on freely available software (including external calls to VisualSFM and CloudCompare), in combination with a low-cost survey design for the reconstruction of a several-hundred-metres-long gully network. SF3M provided a semi-automated workflow for 3-D reconstruction requiring ~ 49 h (of which only 17 % required operator assistance) for obtaining a final gully network model of > 17 million points over a gully plan area of 4230 m2. We show that a walking itinerary along the gully perimeter using two lightweight automatic cameras (1 s time-lapse mode) and a 6 m long pole is an efficient method for 3-D monitoring of gullies, at a low cost (~ EUR 1000 budget for the field equipment) and the time requirements (~ 90 min for image collection). A mean error of 6.9 cm at the ground control points was found, mainly due to model deformations derived from the linear geometry of the gully and residual errors in camera calibration. The straightforward image collection and processing approach can be of great benefit for non-expert users working on gully erosion assessment.
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Castillo, C., M. R. James, M. D. Redel-Macías, R. Pérez, and J. A. Gómez. "The SF3M approach to 3-D photo-reconstruction for non-expert users: application to a gully network." SOIL Discussions 2, no. 1 (April 29, 2015): 371–99. http://dx.doi.org/10.5194/soild-2-371-2015.
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Abstract. 3-D photo-reconstruction (PR) techniques have been successfully used to produce high resolution elevation models for different applications and over different spatial scales. However, innovative approaches are required to overcome some limitations that this technique may present in challenging scenarios. Here, we evaluate SF3M, a new graphical user interface for implementing a complete PR workflow based on freely available software (including external calls to VisualSFM and CloudCompare), in combination with a low-cost survey design for the reconstruction of a several-hundred-meters-long gully network. SF3M provided a semi-automated workflow for 3-D reconstruction requiring ~ 49 h (of which only 17% required operator assistance) for obtaining a final gully network model of > 17 million points over a gully plan area of 4230 m2. We show that a walking itinerary along the gully perimeter using two light-weight automatic cameras (1 s time-lapse mode) and a 6 m-long pole is an efficient method for 3-D monitoring of gullies, at a low cost (about EUR 1000 budget for the field equipment) and time requirements (~ 90 min for image collection). A mean error of 6.9 cm at the ground control points was found, mainly due to model deformations derived from the linear geometry of the gully and residual errors in camera calibration. The straightforward image collection and processing approach can be of great benefit for non-expert users working on gully erosion assessment.
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Pinto, L., F. Bianchini, V. Nova, and D. Passoni. "LOW-COST UAS PHOTOGRAMMETRY FOR ROAD INFRASTRUCTURES’ INSPECTION." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 14, 2020): 1145–50. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-1145-2020.
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Abstract. All over the world, road infrastructures are getting closer to their life cycle and need to be constantly inspected: a consistent number of bridges are structurally deficient, and the risk of collapse can no longer be excluded. In contrast with the past, the interest in structure durability has recently grown rapidly. In order to make bridges durable, it is necessary to carry out ordinary maintenance, preceded by inspection activities, which can be traditionally divided in two categories: destructive and non-destructive (NDT). All the NDT inspections (visual, IR thermography, GPR) can be conducted by using UAS (Unmanned Aerial Systems), a technology that makes bridges inspections quicker, cheaper, objective and repeatable. This study presents the visual inspection and survey of two bridges by using a UAS DJI Mavic 2 Pro, equipped with a 20Mpixel Hasselblad camera that records 60fps 4K video and a 10bit radiometric resolution. Starting from the acquired data, a 3D model of each structure was built by using Structure from Motion (SfM) principles and software. To validate the two models, each of them characterized by a centimetric accuracy, the UAS camera generated cloud of points and was co-registered with the point cloud of a terrestrial laser-scanner using Ground Control Points (GCPs). To make this, CloudCompare comparison software was used; the plugin M3C2 automatically calculates the distance between the points of two compared clouds. Finally, some general rules concerning the UAS main characteristics for inspection of bridges and software for data processing are proposed.
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Oth, Olivier, César Dauchot, Maria Orellana, and Régine Glineur. "How to Sterilize 3D Printed Objects for Surgical Use? An Evaluation of the Volumetric Deformation of 3D-Printed Genioplasty Guide in PLA and PETG after Sterilization by Low-Temperature Hydrogen Peroxide Gas Plasma." Open Dentistry Journal 13, no. 1 (November 5, 2019): 410–17. http://dx.doi.org/10.2174/1874210601913010410.
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Introduction: In the present time, there is rapid development in the application of 3D printing technology in surgery. One of the challenges encountered by the surgeon is the sterilization of these 3D-printed objects for use in the operating room. Materials and Methods: Forty-two identical cutting guides used for genioplasty were 3D-printed: twenty-one in Polylactic acid (PLA) and twenty-one in Polyethylene terephthalate glycol (PETG). The guides were CT scanned after printing. They were then sterilized with the low-temperature hydrogen peroxide gas plasma technique (Sterrad®). A CT scan of the guides was also performed at T1 (after printing) and T2 (after sterilization). A software (Cloudcompare ®) was then used to accurately compare the volume of each guide at T0 (the initial computer-aided designed guide) vs T1 and T1 vs T2. Statistical analysis was then performed. Results: Although there are differences that are statistically significant for each series between T0 and T2 and T1 and T2 for both PLA and PETG, this had no impact on the clinical use of sterilized objects using hydrogen peroxide sterilization technique because these morphological differences were minimal at less than 0.2mm. Conclusion: Morphological deformations induced by the hydrogen peroxide sterilization are sub-millimeter and acceptable for surgical use. The hydrogen peroxide sterilization is, therefore, an alternative to avoid the deformation of 3D-printed objects made from PLA and PETG during conventional steam sterilization (autoclave). To the best of our knowledge, this is the first study regarding the morphologic deformation of 3D-printed objects in PLA and PETG after sterilization for medical use.
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Niederheiser, Robert, Martin Mokroš, Julia Lange, Helene Petschko, Günther Prasicek, and Sander Oude Elberink. "DERIVING 3D POINT CLOUDS FROM TERRESTRIAL PHOTOGRAPHS - COMPARISON OF DIFFERENT SENSORS AND SOFTWARE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 16, 2016): 685–92. http://dx.doi.org/10.5194/isprs-archives-xli-b5-685-2016.
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Terrestrial photogrammetry nowadays offers a reasonably cheap, intuitive and effective approach to 3D-modelling. However, the important choice, which sensor and which software to use is not straight forward and needs consideration as the choice will have effects on the resulting 3D point cloud and its derivatives. <br><br> We compare five different sensors as well as four different state-of-the-art software packages for a single application, the modelling of a vegetated rock face. The five sensors represent different resolutions, sensor sizes and price segments of the cameras. The software packages used are: (1) Agisoft PhotoScan Pro (1.16), (2) Pix4D (2.0.89), (3) a combination of Visual SFM (V0.5.22) and SURE (1.2.0.286), and (4) MicMac (1.0). We took photos of a vegetated rock face from identical positions with all sensors. Then we compared the results of the different software packages regarding the ease of the workflow, visual appeal, similarity and quality of the point cloud. <br><br> While PhotoScan and Pix4D offer the user-friendliest workflows, they are also “black-box” programmes giving only little insight into their processing. Unsatisfying results may only be changed by modifying settings within a module. The combined workflow of Visual SFM, SURE and CloudCompare is just as simple but requires more user interaction. MicMac turned out to be the most challenging software as it is less user-friendly. However, MicMac offers the most possibilities to influence the processing workflow. The resulting point-clouds of PhotoScan and MicMac are the most appealing.
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Diez Castillo, Agustín, Alfredo Cortell Nicolau, Oreto García Puchol, and Pilar Escribá Ruiz. "Entorno 3D para el análisis y la recreación virtual de las actuaciones arqueológicas en Cueva de la Cocina (Dos Aguas, Valencia, España)." Virtual Archaeology Review 8, no. 17 (July 26, 2017): 75. http://dx.doi.org/10.4995/var.2017.7028.
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In this paper we present our procedure for digitising fieldwork information on the fly (data management), and its combination with the virtual reconstruction of the stratigraphy (virtualisation), of the Cueva de la Cocina site in Dos Aguas (Valencia, Spain). The main tool for the Geographic Information System (GIS) implementation has been OpenJUMP, whilst for the three-dimensional (3D) recreation of the cave virtual environment MeshLab, ParaView, CloudCompare and R open software have been used. According to the data recovered during the two last field seasons at the cave -2015 and 2016-, we present the current state of the stratigraphy virtualisation in the excavated sectors. We also provide not only a general view of the cave, but also different points of view to incorporate distinct geomatics tools into archaeological research. The computer treatment of the data collected in the field provides a better understanding of their spatial relations; which in turn facilitates its analysis and interpretation as well as the realisation of virtual profiles. In the same way, the differences in the frequency of materials belonging to adjacent and/or superimposed stratigraphical units, as well as the total quantities, volumetry and density of the artefacts, with respect to their own stratigraphical unit, or even the whole excavated area, can also be analysed. The combination of both approaches -data management and virtualisation- allows us to integrate geographic information technologies in the daily life of the Mesolithic and Neolithic communities, of which the virtual reconstruction of the different test pits carried out in Cueva de la Cocina constitutes a perfect example.
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Niederheiser, Robert, Martin Mokroš, Julia Lange, Helene Petschko, Günther Prasicek, and Sander Oude Elberink. "DERIVING 3D POINT CLOUDS FROM TERRESTRIAL PHOTOGRAPHS - COMPARISON OF DIFFERENT SENSORS AND SOFTWARE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B5 (June 16, 2016): 685–92. http://dx.doi.org/10.5194/isprsarchives-xli-b5-685-2016.
Full textAbstract:
Terrestrial photogrammetry nowadays offers a reasonably cheap, intuitive and effective approach to 3D-modelling. However, the important choice, which sensor and which software to use is not straight forward and needs consideration as the choice will have effects on the resulting 3D point cloud and its derivatives. <br><br> We compare five different sensors as well as four different state-of-the-art software packages for a single application, the modelling of a vegetated rock face. The five sensors represent different resolutions, sensor sizes and price segments of the cameras. The software packages used are: (1) Agisoft PhotoScan Pro (1.16), (2) Pix4D (2.0.89), (3) a combination of Visual SFM (V0.5.22) and SURE (1.2.0.286), and (4) MicMac (1.0). We took photos of a vegetated rock face from identical positions with all sensors. Then we compared the results of the different software packages regarding the ease of the workflow, visual appeal, similarity and quality of the point cloud. <br><br> While PhotoScan and Pix4D offer the user-friendliest workflows, they are also “black-box” programmes giving only little insight into their processing. Unsatisfying results may only be changed by modifying settings within a module. The combined workflow of Visual SFM, SURE and CloudCompare is just as simple but requires more user interaction. MicMac turned out to be the most challenging software as it is less user-friendly. However, MicMac offers the most possibilities to influence the processing workflow. The resulting point-clouds of PhotoScan and MicMac are the most appealing.
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Yan, Zhaojin, Rufei Liu, Liang Cheng, Xiao Zhou, Xiaoguang Ruan, and Yijia Xiao. "A Concave Hull Methodology for Calculating the Crown Volume of Individual Trees Based on Vehicle-Borne LiDAR Data." Remote Sensing 11, no. 6 (March 14, 2019): 623. http://dx.doi.org/10.3390/rs11060623.
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Crown volume is an important tree factor used in forest surveys as a prerequisite for estimating biomass and carbon stocks. This study developed a method for accurately calculating the crown volume of individual trees from vehicle-borne laser scanning (VLS) data using a concave hull by slices method. CloudCompare, an open-source three-dimensional (3D) point cloud and mesh processing software package, was used with VLS data to segment individual trees from which single tree crowns were extracted by identifying the first branch point of the tree. The slice thickness and number to be fitted to the canopy point cloud were adaptively determined based on the change rate in area with height, with the area of each slice calculated using the concave hull algorithm with portions of the crown regarded as truncated cones. The overall volume was then calculated as the sum of all sub-volumes. The proposed method was experimentally validated on 30 urban trees by comparing the crown volumes calculated using the proposed method with those calculated using five existing methods (manual measurement, 3D convex hull, 3D alpha shape, convex hull by slices, and voxel-based). The proposed method produced the smallest average crown volume. Gaps and holes in the point cloud were regarded as part of the crown by the manual measurement, 3D convex hull, and convex hull by slices method, resulting in the calculated volume being higher than the true value; the proposed method reduced this effect. These results indicate that the concave hull by slices method can more effectively calculate the crown volume of a single tree from VLS data.
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Shotton, Elizabeth Anne. "Living in the clouds: conceptual reconstructions of harbour structures." Journal of Cultural Heritage Management and Sustainable Development 8, no. 4 (November 19, 2018): 405–19. http://dx.doi.org/10.1108/jchmsd-08-2017-0052.
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Purpose The harbours of Ireland, under threat from deterioration and rising sea levels, are being documented using terrestrial LiDAR augmented by archival research to develop comprehensive histories and timeline models for public dissemination. While methods to extract legible three-dimensional models from scan data have been developed and such operational formats for heritage management are imperative, the need for this format in interpretive visualisations should be reconsidered. The paper aims to discuss these issues. Design/methodology/approach Interpretive visualisations are forms of history making, where factual evidence is drawn together with conjecture to illustrate a plausible account of events, and differentiation between fact and conjecture is the key to their intellectual transparency. A procedure for superimposing conjectural reconstructions, generated using Rhinoceros and CloudCompare, on original scan data in Cyclone and visualised on a web-based viewer is discussed. Findings Embellishing scan data with conjectural elements to visualise the evolution of harbours is advantageous for both research and public dissemination. The accuracy and density of the scans enables the interrogation of the harbour form and the irregular details, the latter in danger of generalisation if translated into parametric or mesh format. Equally, the ethereal quality of the point cloud conveys a sense of tentativeness, consistent with a provisional hypothesis. Finally, coding conjectural elements allows users to intuit the difference between fact and historical narrative. Originality/value While various web-based point clouds viewers are used to disseminate research, the novelty here is the potential to develop didactic representations using point clouds that successfully capture a provisional thesis regarding each harbour’s evolution in an intellectually transparent manner to enable further inquiry.
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Kermarrec, Paffenholz, and Alkhatib. "How Significant Are Differences Obtained by Neglecting Correlations When Testing for Deformation: A Real Case Study Using Bootstrapping with Terrestrial Laser Scanner Observations Approximated by B-Spline Surfaces." Sensors 19, no. 17 (August 21, 2019): 3640. http://dx.doi.org/10.3390/s19173640.
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B-spline surfaces possess attractive properties such as a high degree of continuity or the local support of their basis functions. One of the major applications of B-spline surfaces in engineering geodesy is the least-square (LS) fitting of surfaces from, e.g., 3D point clouds obtained from terrestrial laser scanners (TLS). Such mathematical approximations allow one to test rigorously with a given significance level the deformation magnitude between point clouds taken at different epochs. Indeed, statistical tests cannot be applied when point clouds are processed in commonly used software such as CloudCompare, which restrict the analysis of deformation to simple deformation maps based on distance computation. For a trustworthy test decision and a resulting risk management, the stochastic model of the underlying observations needs, however, to be optimally specified. Since B-spline surface approximations necessitate Cartesian coordinates of the TLS observations, the diagonal variance covariance matrix (VCM) of the raw TLS measurements has to be transformed by means of the error propagation law. Unfortunately, this procedure induces mathematical correlations, which can strongly affect the chosen test statistics to analyse deformation, if neglected. This may lead potentially to rejecting wrongly the null hypothesis of no-deformation, with risky and expensive consequences. In this contribution, we propose to investigate the impact of mathematical correlations on test statistics, using real TLS observations from a bridge under load. As besides TLS, a highly precise laser tracker (LT) was used, the significance of the difference of the test statistics when the stochastic model is misspecified can be assessed. However, the underlying test distribution is hardly tractable so that only an adapted bootstrapping allows the computation of trustworthy p-values. Consecutively, the extent to which heteroscedasticity and mathematical correlations can be neglected or simplified without impacting the test decision is shown in a rigorous way, paving the way for a simplification based on the intensity model.
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Di Rita, M., D. Fugazza, V. Belloni, G. Diolaiuti, M. Scaioni, and M. Crespi. "GLACIER VOLUME CHANGE MONITORING FROM UAV OBSERVATIONS: ISSUES AND POTENTIALS OF STATE-OF-THE-ART TECHNIQUES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2020 (August 12, 2020): 1041–48. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2020-1041-2020.
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Abstract. Alpine glaciers play a key role in our society through the production of freshwater for domestic, industrial and agricultural use. As they are severely affected by climate change, it is of crucial importance to understand their behaviour and monitor their morphological evolution, with the primary aims to estimate ice volume and mass changes. However, the accurate retrieval of glacier morphology changes over time is not an easy task. In this context, the use of Unmanned Aerial Vehicles (UAVs) is of interest to the glaciological community because of their flexibility, fine spatial detail and ease of processing with state-of-the-art software packages, which makes them an ideal candidate to investigate glacier changes. The goal of this work is to assess the accuracy that can be obtained with UAVs observations when comparing volume changes computed from multi-temporal acquisitions on an Alpine glacier, on the basis of a photogrammetric pipeline implemented in Leica Infinity software. The study area is Forni Glacier in Raethian Alps, Italy. Two photogrammetric blocks were acquired in 2014 and 2016 using different UAVs: a fixed-wing drone in 2014 and an in-house multicopter in 2016. Ground Control Points (GCPs) were established only during the 2016 survey which was used to establish the reference datum. Different techniques to co-register the 2014 dataset to the 2016 dataset were applied and compared: 1) using points extracted from the 2016 Dense Point Cloud (DPC) as GCPs for the 2014 DPC generation; 2) shifting and rotating the raw 2014 DPC, using manually digitised common points from the 2014 and 2016 DPCs in Leica Infinity; 3) first manually shifting, then automatically roto-translating with the Iterative Closest Point (ICP) algorithm the raw 2014 DPC in CloudCompare. The investigation shows a good agreement of the three co-registration methods in terms of height and ice volume changes and the potential of UAV data processing with Leica Infinity for glacier monitoring even when the acquisition conditions are problematic (lack of ground control points, sub-optimal image quality).
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Thoeni, K., A. Giacomini, R. Murtagh, and E. Kniest. "A comparison of multi-view 3D reconstruction of a rock wall using several cameras and a laser scanner." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-5 (June 6, 2014): 573–80. http://dx.doi.org/10.5194/isprsarchives-xl-5-573-2014.
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This work presents a comparative study between multi-view 3D reconstruction using various digital cameras and a terrestrial laser scanner (TLS). Five different digital cameras were used in order to estimate the limits related to the camera type and to establish the minimum camera requirements to obtain comparable results to the ones of the TLS. The cameras used for this study range from commercial grade to professional grade and included a GoPro Hero 1080 (5 Mp), iPhone 4S (8 Mp), Panasonic Lumix LX5 (9.5 Mp), Panasonic Lumix ZS20 (14.1 Mp) and Canon EOS 7D (18 Mp). The TLS used for this work was a FARO Focus 3D laser scanner with a range accuracy of ±2 mm. The study area is a small rock wall of about 6 m height and 20 m length. The wall is partly smooth with some evident geological features, such as non-persistent joints and sharp edges. Eight control points were placed on the wall and their coordinates were measured by using a total station. These coordinates were then used to georeference all models. A similar number of images was acquired from a distance of between approximately 5 to 10 m, depending on field of view of each camera. The commercial software package PhotoScan was used to process the images, georeference and scale the models, and to generate the dense point clouds. Finally, the open-source package CloudCompare was used to assess the accuracy of the multi-view results. Each point cloud obtained from a specific camera was compared to the point cloud obtained with the TLS. The latter is taken as ground truth. The result is a coloured point cloud for each camera showing the deviation in relation to the TLS data. The main goal of this study is to quantify the quality of the multi-view 3D reconstruction results obtained with various cameras as objectively as possible and to evaluate its applicability to geotechnical problems.
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Magtalas, M. S. L. Y., J. C. L. Aves, and A. C. Blanco. "GEOREFERENCING UAS DERIVATIVES THROUGH POINT CLOUD REGISTRATION WITH ARCHIVED LIDAR DATASETS." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W1 (October 5, 2016): 195–99. http://dx.doi.org/10.5194/isprs-annals-iv-2-w1-195-2016.
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Georeferencing gathered images is a common step before performing spatial analysis and other processes on acquired datasets using unmanned aerial systems (UAS). Methods of applying spatial information to aerial images or their derivatives is through onboard GPS (Global Positioning Systems) geotagging, or through tying of models through GCPs (Ground Control Points) acquired in the field. Currently, UAS (Unmanned Aerial System) derivatives are limited to meter-levels of accuracy when their generation is unaided with points of known position on the ground. The use of ground control points established using survey-grade GPS or GNSS receivers can greatly reduce model errors to centimeter levels. However, this comes with additional costs not only with instrument acquisition and survey operations, but also in actual time spent in the field. This study uses a workflow for cloud-based post-processing of UAS data in combination with already existing LiDAR data. The georeferencing of the UAV point cloud is executed using the Iterative Closest Point algorithm (ICP). It is applied through the open-source CloudCompare software (Girardeau-Montaut, 2006) on a ‘skeleton point cloud’. This skeleton point cloud consists of manually extracted features consistent on both LiDAR and UAV data. For this cloud, roads and buildings with minimal deviations given their differing dates of acquisition are considered consistent. Transformation parameters are computed for the skeleton cloud which could then be applied to the whole UAS dataset. In addition, a separate cloud consisting of non-vegetation features automatically derived using CANUPO classification algorithm (Brodu and Lague, 2012) was used to generate a separate set of parameters. Ground survey is done to validate the transformed cloud. An RMSE value of around 16 centimeters was found when comparing validation data to the models georeferenced using the CANUPO cloud and the manual skeleton cloud. Cloud-to-cloud distance computations of CANUPO and manual skeleton clouds were obtained with values for both equal to around 0.67 meters at 1.73 standard deviation.
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Sayab, Mohammad, Domingo Aerden, Markku Paananen, and Petri Saarela. "Virtual Structural Analysis of Jokisivu Open Pit Using ‘Structure-from-Motion’ Unmanned Aerial Vehicles (UAV) Photogrammetry: Implications for Structurally-Controlled Gold Deposits in Southwest Finland." Remote Sensing 10, no. 8 (August 16, 2018): 1296. http://dx.doi.org/10.3390/rs10081296.
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Unmanned aerial vehicles (UAVs) are rapidly growing remote sensing platforms for capturing high-resolution images of exposed rock surfaces. We used a DJI Phantom 3 Professional (P3P) quadcopter to capture aerial images that were used to generate a high-resolution three-dimensional (3-D) model of the Jokisivu open-pit gold deposit that is located in southwestern Finland. 158 overlapping oblique and nadir images were taken and processed with Agisoft Photoscan Pro to generate textured 3-D surface models. In addition, 69 overlapping images were taken from the steep faces of the open pit. We assessed the precision of the 3-D model by deploying ground control points (GCPs) and the average errors were found minimal along X (2.0 cm), Y (1.2 cm), and Z (5.0 cm) axes. The steep faces of the open pit were used for virtual structural measurements and kinematic analyses in CloudCompare and ArcGIS to distinguish the orientation of different fracture sets and statistical categorization, respectively. Three distinct fracture sets were observed. The NW-SE and NE-SW striking fractures form a conjugate geometry, whereas the NNW-SSE striking fractures cut the conjugate fracture set. The orientation of conjugate fractures match well with the resource model of the deposit and NW- and NE-trending segments of regional-scale anastomosing shear zones. Based on the conjugate geometry of fracture sets I and II, and the regional pattern of anastomosing shear system lead us to interpret an origin of gold mineralization in two stages. An early N-S or NNW-SSE crustal shortening, corresponding to the regional D4 (ca. 1.83–1.81 Ga) or pre-D4 (ca. 1.87–1.86 Ga) Svecofennian tectonic event(s) that produced anastomosing shear zones. Subsequent E-W directed D5 contraction (ca. 1.79–1.77 Ga) partly reactivated the anastomosing shear zones with the formation of conjugate system, which controlled the migration of fluids and gold mineralization in SW Finland.
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Pavelka, Karel, Jaroslav Šedina, and Karel Pavelka. "Knud Rasmussen Glacier Status Analysis Based on Historical Data and Moving Detection Using RPAS." Applied Sciences 11, no. 2 (January 14, 2021): 754. http://dx.doi.org/10.3390/app11020754.
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This article discusses partial results of an international scientific expedition to Greenland that researched the geography, geodesy, botany, and glaciology of the area. The results here focus on the photogrammetrical results obtained with the eBee drone in the eastern part of Greenland at the front of the Knud Rasmussen Glacier and the use of archive image data for monitoring the condition of this glacier. In these short-term visits to the site, the possibility of using a drone is discussed and the results show not only the flow speed of the glacier but also the shape and structure from a height of up to 200 m. From two overflights near the glacier front at different times, it was possible to obtain the speed of the glacier flow and the distribution of velocities in the glacier stream. The technology uses a comparison of two point clouds derived from a set of aerial photos taken with the eBee drone, and calculating the M3C2 (Multiscale Model-to-Model Cloud Comparison) distances with CloudCompare software. The results correlate with other measurement methods like accurate and long-term measurement with Global Navigation Satellite System (GNSS), satellite radar, or ground geodetical technology. The resulting speed from the drone data reached in the middle part of the glacier, was approximately 12–15m per day. The second part of the paper focuses on the analysis of modern satellite images of the Knud Rasmussen Glacier from Google Earth (Landsat series 1984–2016) and Sentinel 2a, and a comparison with historical aerial images from 1932 to 1933. Historical images were processed photogrammetrically into a three-dimensional (3D) model. Finally, orthogonalized image data from three systems (drone photos, historical aerial photos, and satellite data) were compared in the ArcGIS software. This allows us to analyze glacier changes over time in the time span from 1932 to 2020, with the caveat that from 1933 to 1983 we did not have data at our disposal. The result shows that more significant changes in the area of this glacier occurred after 2011. The main aim of this article is to research the use of photogrammetric methods for monitoring the condition and parameters of glaciers based on non-traditional technology, such as drones or new processing of historical photos.
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Mat Zam, P. M., N. A. Fuad, A. R. Yusoff, and Z. Majid. "EVALUATING THE PERFORMANCE OF TERRESTRIAL LASER SCANNING FOR LANDSLIDE MONITORING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W9 (October 26, 2018): 35–55. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w9-35-2018.
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<p><strong>Abstract.</strong> Nowadays, Terrestrial Laser Scanning (TLS) technology is gaining popularity in monitoring and predicting the movement of landslide due to the capability of high-speed data capture without requiring a direct contact with the monitored surface. It offers very high density of point cloud data in high resolution and also can be an effective tool in detecting the surface movement of the landslide area. The aim of this research is to determine the optimal level of scanning resolution for landslide monitoring using TLS. The Topcon Geodetic Laser Scanner (GLS) 2000 was used in this research to obtain the three dimensional (3D) point cloud data of the landslide area. Four types of resolution were used during scanning operation which were consist of very high, high, medium and low resolutions. After done with the data collection, the point clouds datasets were undergone the process of registration and filtering using ScanMaster software. After that, the registered point clouds datasets were analyzed using CloudCompare software. Based on the results obtained, the accuracy of TLS point cloud data between picking point manually and computed automatically by ScanMaster software shows the maximum Root Mean Square (RMS) value of coordinate differences were 0.013<span class="thinspace"></span>m in very high resolution, 0.017<span class="thinspace"></span>m in high resolution, 0.031<span class="thinspace"></span>m in medium resolution and 0.052<span class="thinspace"></span>m in low resolution respectively. Meanwhile, the accuracy of TLS point cloud data between picking point manually and total station data using intersection method shows the maximum RMS values of coordinate differences were 0.013<span class="thinspace"></span>m in very high resolution, 0.018<span class="thinspace"></span>m in high resolution, 0.033<span class="thinspace"></span>m in medium resolution and 0.054<span class="thinspace"></span>m in low resolution respectively. Hence, it can be concluded that the high or very high resolution is needed for landslide monitoring using Topcon GLS-2000 which can provide more accurate data in slope result, while the low and medium resolutions is not suitable for landslide monitoring due to the accuracy of TLS point cloud data that will decreased when the resolution value is increased.</p>
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Yeshwanth Kumar, A., M. A. Noufia, K. A. Shahira, and A. M. Ramiya. "BUILDING INFORMATION MODELLING OF A MULTI STOREY BUILDING USING TERRESTRIAL LASER SCANNER AND VISUALISATION USING POTREE: AN OPEN SOURCE POINT CLOUD RENDERER." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W17 (November 29, 2019): 421–26. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w17-421-2019.
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Abstract. With the rapid development in infrastructure, the need to document man-made structures is in increasing demand and inevitable. Such a process of digital documentation of buildings is called Building Information Modelling (BIM). Conventional techniques of BIM involve manual drafting & modelling using computer aided design, drafting & modelling software. Although these techniques are more accurate, given the increase in the size and complexity of modern structures, it would be tedious and time consuming for such manual work. It is in this context LiDAR shows great potential to simplify this task. Laser scanning enables rapid mapping of a building with a high degree of spatial accuracy. Since the spatial point sampling distance of any LiDAR scanner is usually in the order of centimetres or millimetres, this has potential not only to generate high density scans of the building but also to identify even the smallest defects in a structure. This facilitates using LiDAR to study the serviceability of a building. In this project, the feasibility of using a terrestrial laser scanner (TLS) to scan a multi-storey building was investigated. Additionally, the reliability of Potree for visualising point cloud data was tested. Potree is an open-source WebGL based point cloud renderer. Potree enables us to render point clouds and visualise in a portable web application. This application is also capable of making measurements of high accuracy on the 3D model of the library. This could serve to be of great utility in surveying applications. The object of study was chosen as a six-storey building, each floor having differing layouts. Two of these storeys were below ground surface level which also proved to be a test for the reliability of TLS in challenging terrain. The building has a towering height and large footprint which made it a perfect candidate for this project. A total of 54 scans (44 interior scans and 10 exterior scans of the library) were acquired with each subsequent scan station not more than 10m apart from the previous one. This data was brought to the lab for further processing. The processing was carried out using open-source software packages (LAStools, CloudCompare, etc). After processing, the complete point cloud data had 483,292,994 points. In order to make the data easier to handle, spatial sub-sampling of the data was done after which the final point cloud had 87,789,548 points. Finally, this sub-sampled point cloud was published using the open source Potree Converter into an interactive web application.
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Fuentes-Porto, Alba, Carlos García-Ávila, and Efraín Marrero-Salas. "Casa del Samarín, una estación de grabados rupestres en deterioro. Documentación, análisis y diagnóstico en Los Llanos de Ifara, Granadilla, Tenerife." Virtual Archaeology Review 12, no. 24 (January 19, 2021): 99. http://dx.doi.org/10.4995/var.2021.13810.
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<p class="VARAbstract"><strong>Extended Abstract:</strong></p><p class="VARAbstract">In the archaeology of the Canary Islands (Spain), there are many studies based on the usage of new technologies to contribute to the identification and description of rock art engravings through high-resolution digital models (<a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Mart%C3%ADn_2005">Martín, 2005</a>; <a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Mart%C3%ADn_2007">Martín, Velasco, González & Ramírez, 2007;</a> <a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Senen_2016">Senén & Cuenca, 2016</a>; <a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Navarro_2019">Navarro & Cancel, 2019</a>). This paper is supported by these documentation techniques and digital analysis in order to deepen into the characterization of the damaged rock art station Casa del Samarín (House of Samarín), or Tagoro del Rey, in Los Llanos de Ifara, south of the island of Tenerife (Figs. 1). Twenty-one panels conserved in situ were documented (Fig. 6). Geometric-linear, geometric with an oval and rectangular trend and figurative ones can be distinguished. The blocks <a title="" href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#_ftn1">[1]</a> that compose the engravings station belong to a rocky basalt outcrop, to which other free-standing blocks are attached, forming a circle. The shape that describes this set of blocks is defined as a "cabin" or circular-shaped structure.</p><p class="VARAbstract">This set of engravings, made on a basalt rocky outcrop with a planar factory, show a tendency to suffer from exfoliation and are affected by internal stresses. The intrinsic characteristics of this stone support, together with their exposure to anthropic actions and strong insolation, condition its fragility, with the risk of losing part of the representations that it houses. Given the threat posed by its gradual deterioration, we seek to ensure its digital preservation through precision three-dimensional (3D) records, the engravings inventory, the record of their conservation state and the understanding of the degradation processes that are affecting the outcrop. What has been explained will be addressed quarterly, to observe the evolution of any material changes every three months.</p><p class="VARAbstract">The registration work consisted of taking four photogrammetric surveys in eight months; the surveys were georeferenced by means of a centimetric Global Navigation Satellite System (GNSS) and a total station. Structure from Motion (SfM) technology enabled the researchers to generate high-precision 3D models in an affordable way, not only in terms of cost but also ease of use. Digital copies with Geographic Information System GIS technology were extracted from them, being exportable in shapefile format (Fig. 7).</p><p class="VARAbstract">As regards the documentation of existing pathologies, assuming standardized lexicon and classification criteria (<a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#IPCE_2013">IPCE, 2013</a>), together with a rigorous information systematization, was key for achieving agile handling of the data collected and for facilitating monitoring tasks (Fig. 8). Damage maps were created for collecting the location and scope of the alterations. The complex volumetry of the outcrop and the varied orientation of the panels marked the need to resort to 3D editing so that all their faces could be properly registered (Fig. 10). This project was performed with a 3D design program, Blender®. </p><p class="VARAbstract">Thanks to an imaging analysis process, internal textures of 3D models also provided relevant graphic support for the pictographic content and the conservation state (Figs. 11 & 14). DStretch® (<a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Harman_2008">Harman, 2008</a>), a plugin implemented in the scientific image processing software ImageJTM, was used for this purpose. To conclude, researchers relied on CloudCompare (<a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Girardeau_2015">Girardeau-Montaut, 2015</a>), an advanced 3D data processing software, to tackle a morphometric analysis that allowed us to detect the appearance of formal changes along with the recorded sequences (Figs. 12 & 15). In this process, the distances between two records, taken after six months, were computed with the Cloud to Mesh (C2M) tool, based on the Chamfer distance algorithm (<a href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#Ruiz_2016">Ruiz et al., 2016: 120</a>).</p><p>Registration file cards and damage maps clearly highlighted the main conditions: material losses (shown in orange) and breaks (in green) have affected the outcrop in a generalized way. Furthermore, sedimentary deposits (blue) are concentrated in interstices; while lichen colonies (idem) do so in the least sun-exposed areas. The use of DStretch® highlighted modern excoriations of anthropogenic origin and contributed to distinguishing recent material losses from the older ones, already affected by an incipient patina. Finally, thanks to morphological analysis, a new detachment (Fig. 15b) and a generalized displacement of exempt elements (Figs. 12 & 15) were detected. These displacements indicate outstanding manipulation, which could lead to decontextualizations or new fragmentations.</p><p>Regarding the archaeological interpretation, macroscopic observation of exempt blocks located in the vicinity of the station and the zenith representation of the immediate environment from photogrammetry, have shown that they are forming a set of attached structures (Fig. 13). The site redefinition and the diagnosis of its very weakened defensive system show the need to intensify the archaeological study of this area, so emblematic for the archaeology of the south of Tenerife, in addition to establishing preventive conservation measures that can contribute to its stabilization.</p><p class="VARAbstract"> </p><div><hr align="left" size="1" width="33%" /><div><p><a title="" href="file:///L:/PC%20Port%C3%A1til%20Poli/Mis%20documentos/VAR/En%20Curso/Revisi%C3%B3n/13810/13810-60985-2-CE_jll.docx#_ftnref1">[1]</a> Geological unit of size greater than 300 mm, term standardized by the USCS (Unified Soil Classification System).</p></div></div>
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Chen, Na, Chang-jie Du, and Xiang Ding. "Intelligent Interpretation of the Geometric Properties of Rock Mass Discontinuities Based on an Unmanned Aerial Vehicle." Frontiers in Earth Science 9 (August 5, 2021). http://dx.doi.org/10.3389/feart.2021.711866.
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The geometric properties of rock mass discontinuities are essential for the evaluation of the safety of rock masses. Numerous studies have recently been performed on the extraction of discontinuity information. However, most methods are characterized by poor data collection and processing efficiency. This paper presents a UAV-based methodology for the accurate and complete acquisition of rock surface data, as well as the automatic extraction of discontinuity information. Moreover, a program called Random Sample Consensus (RANSAC) Discontinuity Detection (RDD) is developed to extract discontinuity information based on the proposed method. The conclusions of this research are as follows. 1) RANSAC Discontinuity Detection (RDD) can identify the feature point set of discontinuities from a raw point cloud, and can calculate the discontinuity orientation. 2) The boundary of a discontinuity can be precisely depicted using the improved Graham scan algorithm. 3) The orientations of marked discontinuities extracted by RDD are compared with those extracted by the three-point method in CloudCompare. The differences in the orientations extracted by the two methods are found to be less than 3° for flat discontinuities and only about 4.87° for rough discontinuities, which are within a reasonable error range in practical engineering applications. Therefore, the feasibility of the proposed method is verified.
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Kaňuk, Ján, Jozef Šupinský, Ján Šašak, Jaroslav Hofierka, Yongbo Wang, Qiuzhao Zhang, Vladimír Sedlák, Katarína Onačillová, and Michal Gallay. "Semi-automatic LiDAR point cloud denoising using a connected-component labelling method." Geographia Cassoviensis 13, no. 2 (2019). http://dx.doi.org/10.33542/gc2019-2-08.
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The Smart City concept requires new, fast methods for collection of 3-D data representing features of urban landscape. Laser scanning technology (LiDAR - Light Detection and Ranging) enables such approach producing dense 3-D point clouds of millions of points, which, however, contain noise. Therefore, we developed a new approach allowing for a semi-automatic elimination of data noise resulting from motion of objects within the scanned scene such as persons. We used a connected-component labelling method to filter out the noise points from terrestrial laser scanning point clouds. Our approach was based on a step-by-step object classification with a proper parameterisation. In the first step, all points located close to the predicted terrain were selected. In the second step, the points representing the terrain and floor were classified using the surface filter tool implemented in the RiScan Pro software by RIEGL. The rest of points were classified using point cloud clustering via the connected-component labelling method implemented in the CloudCompare software. In the final step, the operator manually decides whether the point cluster represents the noise. The method was applied to the Cathedral of Saint Elizabeth, a sacral object located in the historical centre of the city of Košice in Slovakia during normal operating hours. We managed to capture approximately 80% of the data noise in total. The method provides a better flexibility in surveying overcrowded city locations using the laser scanning technology.
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Shirshin, Aleksandr V., Igor S. Zheleznyak, Sergei V. Kushnarev, Vladimir N. Malakhovsky, and Natalia S. Gorina. "Evaluation of geometric deviations in rapid prototyped phantoms created from medical imaging data (on the example of computed tomography)." Digital Diagnostics, August 16, 2021. http://dx.doi.org/10.17816/dd63680.
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Aim of study. To evaluate the geometric deviations associated with creation of physical objects from computed tomography data using computer-aided design and additive manufacturing.
Materials and methods. The source object was created using the FreeCAD application; Blender and Meshmixer software was used for polygon meshes correction and transformation. 3D printing was carried out on an Ender-3 printer with copper-impregnated polylactide plastic BFCopper. Scanning was performed using a 128-slice tomograph Philips Ingenuity CT. A series of tomographic images were processed in 3DSlicer software, used to create virtual models by semiautomatic segmentation with threshold values of 500 HU, 0 HU, -500 HU, -750 HU and manual segmentation. Reproduced and reference polygon meshes were compared using Iterative Closest Point algorithm in CloudCompare software.
Results. Reproduced models volume exceeded the volume of respective reference models by 1-27%. The average point cloud linear deviation values of reproduced models from the reference ones were 0.03-0.41 mm. A significant correlation between integral sums of linear deviations and changes in the volume of reproduced models was shown using Spearman's rank correlation coefficient ( = 0.83; temp = 5.27, significance level p = 0.05).
Conclusion. The geometry of the reproduced object changes inevitably, while the linear deviations depend more on the chosen segmentation method rather than on the overall size of the model or its structures. Manual segmentation method can lead to greater linear deviations, though it allows to save all the necessary structures.