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Detection of periodic displacements of shell structures with edges using spline surfaces, meshes and point clouds / Grzegorz Lenda in Reports on geodesy and geoinformatics, vol 112 n° 1 (December 2021)  

Public [article]  inReports on geodesy and geoinformatics > vol 112 n° 1 (December 2021) . - pp 27 - 33 Titre : Detection of periodic displacements of shell structures with edges using spline surfaces, meshes and point clouds Type de document : Article/Communication Auteurs : Grzegorz Lenda, Auteur ; Katarzyna Abrachamowicz, Auteur Année de publication : 2021 Article en page(s) : pp 27 - 33 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] déformation d'édifice [Termes IGN] fonction spline [Termes IGN] maillage [Termes IGN] semis de points [Termes IGN] Triangulated Irregular Network Résumé : (auteur) This research paper tackles the problem of determining displacements of complex-shaped shell structures, measured periodically using laser scanning. Point clouds obtained during different measurement epochs can be compared with each other directly or they can be converted into continuous models in the form of a triangle mesh or smooth patches (spline functions). The accuracy of the direct comparison of point clouds depends on the scanning density, while the accuracy of comparing the point cloud to the model depends on approximation errors that are formed during its creation. Modelling using triangle meshes flattens the local structure of the object compared to the spline model. However, if the shell has edges in its structure, their exact representation by spline models is impossible due to the undulations of functions along them. Edges can also be distorted by the mesh model by their chamfering with transverse triangles. These types of surface modelling errors can lead to the generation of pseudo-deformation of the structure, which is difficult to distinguish from real deformation. In order to assess the possibility of correct determination of deformation using the above-mentioned methods, laser scanning of a complex shell structure in two epochs was performed. Then, modelling and comparison of the results of periodic measurements were carried out. As a result of the research, advantages and disadvantages of each method were identified. It was noticed that none of the methods made it possible to correctly represent all deformations while suppressing pseudo-deformation. However, the combination of their best qualities made it possible to determine the actual deformation of the structure. Numéro de notice : A2021-962 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.2478/rgg-2021-0005 Date de publication en ligne : 17/12/2021 En ligne : https://doi.org/10.2478/rgg-2021-0005 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=100114 [article]

Laser scanning in engineering surveying : methods of measurement and modeling of structures / Grzegorz Lenda in Reports on geodesy and geoinformatics, vol 100 (May 2016)  

Public [article]  inReports on geodesy and geoinformatics > vol 100 (May 2016) . - pp 109 - 130 Titre : Laser scanning in engineering surveying : methods of measurement and modeling of structures Type de document : Article/Communication Auteurs : Grzegorz Lenda, Auteur ; Andrzej Uznański, Auteur ; Michal Strach, Auteur ; Paulina Lewińska, Auteur Année de publication : 2016 Article en page(s) : pp 109 - 130 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes IGN] données lidar [Termes IGN] données localisées 3D [Termes IGN] semis de points [Termes IGN] télémétrie laser aéroporté [Termes IGN] télémétrie laser mobile [Termes IGN] télémétrie laser terrestre Résumé : (Auteur) The study is devoted to the uses of laser scanning in the field of engineering surveying. It is currently one of the main trends of research which is developed at the Department of Engineering Surveying and Civil Engineering at the Faculty of Mining Surveying and Environmental Engineering of AGH University of Science and Technology in Krakow. They mainly relate to the issues associated with tower and shell structures, infrastructure of rail routes, or development of digital elevation models for a wide range of applications. These issues often require the use of a variety of scanning techniques (stationary, mobile), but the differences also regard the planning of measurement stations and methods of merging point clouds. Significant differences appear during the analysis of point clouds, especially when modeling objects. Analysis of the selected parameters is already possible basing on ad hoc measurements carried out on a point cloud. However, only the construction of three-dimensional models provides complete information about the shape of structures, allows to perform the analysis in any place and reduces the amount of the stored data. Some structures can be modeled in the form of simple axes, sections, or solids, for others it becomes necessary to create sophisticated models of surfaces, depicting local deformations. The examples selected for the study allow to assess the scope of measurement and office work for a variety of uses related to the issue set forth in the title of this study. Additionally, the latest, forward-looking technology was presented - laser scanning performed from Unmanned Aerial Vehicles (drones). Currently, it is basically in the prototype phase, but it might be expected to make a significant progress in numerous applications in the field of engineering surveying. Numéro de notice : A2016-648 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1515/rgg-2016-0010 En ligne : http://dx.doi.org/10.1515/rgg-2016-0010 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81854 [article]