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Integrated georeferencing for precise depth map generation exploiting multi-camera image sequences from mobile mapping / Stefan Cavegn (2020)
Titre : Integrated georeferencing for precise depth map generation exploiting multi-camera image sequences from mobile mapping Type de document : Thèse/HDR Auteurs : Stefan Cavegn, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2020 Collection : DGK - C, ISSN 0065-5325 num. 863 Note générale : bibliographie
Dissertation zur Erlangung des Grades Doktor-Ingenieur (Dr.-Ing.)
Diese Arbeit ist gleichzeitig veröffentlicht in: Wissenschaftliche Arbeiten der Fachrichtung Geodäsie der Universität StuttgartLangues : Anglais (eng) Résumé : (auteur) Image-based mobile mapping systems featuring multi-camera configurations allow for efficient geospatial data acquisition in both outdoor and indoor environments. We aim at accurate geospatial 3D image spaces consisting of collections of georeferenced multi-view RGB-D imagery, which may serve as basis for 3D street view services. In order to obtain high-quality depth maps, dense image matching exploiting multi-view image sequences captured with high redundancy needs to be performed. Since this process is entirely dependent on accurate image orientations, we mainly focus on pose estimation of multi-camera systems within this thesis. Nonetheless, we also present methods and investigations to obtain accurate, reliable and complete 3D scene representations based on multi-stereo mobile mapping sequences. Conventional image orientation approaches such as direct georeferencing enable absolute accuracies at the centimeter level in open areas with good GNSS coverage. However, GNSS conditions of street-based mobile mapping in urban canyons are often deteriorated by multipath effects and by shading of the signals caused by vegetation and large multi-story buildings. Moreover, indoor spaces do not even allow for any GNSS signals. Hence, we propose a powerful and versatile image orientation procedure that is able to cope with these issues encountered in challenging urban environments. Our integrated georeferencing approach extends the powerful structure-from-motion pipeline COLMAP with georeferencing capabilities. It assumes initial camera poses with sub-meter accuracy, which allow for direct triangulation of the complete scene. Such a global approach is much more efficient than an incremental structure-from-motion procedure. Furthermore, an initial image orientation solution already facilitates to georeference in a geodetic reference frame. Nevertheless, accuracies at the centimeter level can only be achieved by incorporation of ground control points. In order to obtain sub-pixel accurate relative orientations, strong tie point connections for the highly redundant multi-view image sequences are required. However, hardly overlapping fields of view, strongly varying views and weakly textured surfaces aggravate image feature matching. Hence, constraining relative orientation parameters among cameras is crucial for accurate, robust and efficient image orientation. Apart from supporting fixed multi-camera rigs, our integrated georeferencing approach that uses bundle adjustment allows for self-calibration of all relative orientation parameters or just single components. We extensively evaluated our integrated georeferencing procedure using six challenging real-world datasets in order to demonstrate its accuracy, robustness, efficiency and versatility. Four datasets were captured outdoors, one by a rail-based and three by different street-based multi-stereo camera systems. A portable mobile mapping system featuring a multi-head panorama camera collected two datasets in an indoor environment. Employing relative orientation constraints and ground control points within these indoor spaces resulted in absolute 3D accuracies of ca. 2 cm, and precisions at the millimeter level for relative 3D measurements. Depending on the use case, absolute 3D accuracy values for outdoor environments are slightly larger and amount to a few centimeters. However, determining 3D reference coordinates is a costly task. Not relying on any ground control points led to horizontal accuracies of ca. 5 cm for a scenario featuring some loops, while dropping down to a few decimeters for an extended junction area. Since the height component is even more dependent on prior camera poses from direct georeferencing, these 2D accuracies significantly decreased for the 3D case. However, incorporating just one ground control point facilitates the elimination of systematic effects, which results in 3D accuracies within the sub-decimeter range. Nevertheless, at least one additional check point is recommended in order to ensure a reliable solution. Once consistent and sub-pixel accurate relative poses of spatially adjacent images are available, in-sequence dense image matching can be performed. Aiming at precise and dense depth map generation, we evaluated several image matching configurations. Standard single stereo matching led to high accuracies, which could not significantly be improved by in-sequence matching. However, the image redundancy provided by additional epochs resulted in more complete and reliable depth maps. Note de contenu : 1- Introduction
2- From imagery to 3D geometry
3- Developped methods for integrated georeferencing
4- Evaluation of integrated georeferencing
5- Evaluation of In-sequence dense image matching
6- Conclusion and outlookNuméro de notice : 17679 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Note de thèse : PhD thesis : Ingénierie aérospatiale et géodésie : Stuttgart : 2020 En ligne : https://dx.doi.org/10.18419/opus-11210 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98019 On a novel 360° panoramic stereo mobile mapping system / Stefan Blaser in Photogrammetric Engineering & Remote Sensing, PERS, vol 84 n° 6 (juin 2018)
[article]
Titre : On a novel 360° panoramic stereo mobile mapping system Type de document : Article/Communication Auteurs : Stefan Blaser, Auteur ; Stephan Nebiker, Auteur ; Stefan Cavegn, Auteur Année de publication : 2018 Article en page(s) : pp 347 - 356 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Acquisition d'image(s) et de donnée(s)
[Termes IGN] chambre panoramique
[Termes IGN] image panoramique
[Termes IGN] modèle 3D de l'espace urbain
[Termes IGN] reconstruction 3D du bâti
[Termes IGN] système de numérisation mobileRésumé : (auteur) Image-based mobile mapping systems enable the efficient acquisition of georeferenced image sequences, which can later be exploited in cloud-based 3D geoinformation services. In order to provide a 360° coverage with accurate 3D measuring capabilities, we present a novel 360° panoramic stereo camera configuration. By using two 360° panorama cameras tilted forward and backward in combination with conventional forward and backward looking stereo camera sytems, we achieve a full 360° multi-stereo coverage. We furthermore developed a new mobile mapping system based on our proposed approach, which is operational and fulfills our high accuracy requirements. We successfully implemented a rigorous sensor and system calibration procedure, which allows calibrating all stereo systems with a superior accuracy compared to that of previous work. Our study delivered absolute 3D point accuracies in the range of 2 to 8 cm and relative accuracies of 3D distances in the range of 1 to 5 cm. We achieved these results in a challenging urban area. Furthermore, we automatically reconstructed a 3D city model of our study area by employing all captured and georeferenced mobile mapping imagery. The result is a highly detailed and almost complete 3D city model of the street-level environment. Numéro de notice : A2018-228 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.84.6.347 Date de publication en ligne : 01/06/2018 En ligne : https://doi.org/10.14358/PERS.84.6.347 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=90164
in Photogrammetric Engineering & Remote Sensing, PERS > vol 84 n° 6 (juin 2018) . - pp 347 - 356[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 105-2018061 RAB Revue Centre de documentation En réserve L003 Disponible Image-based mobile mapping for 3D Urban data capture / Stefan Cavegn in Photogrammetric Engineering & Remote Sensing, PERS, vol 82 n° 12 (December 2016)
[article]
Titre : Image-based mobile mapping for 3D Urban data capture Type de document : Article/Communication Auteurs : Stefan Cavegn, Auteur ; Norbert Haala, Auteur Année de publication : 2016 Article en page(s) : pp 925 - 933 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie terrestre
[Termes IGN] acquisition de données
[Termes IGN] appariement d'images
[Termes IGN] géoréférencement direct
[Termes IGN] image multicapteur
[Termes IGN] image terrestre
[Termes IGN] lever mobile
[Termes IGN] milieu urbain
[Termes IGN] reconstruction 3D
[Termes IGN] semis de points
[Termes IGN] système de numérisation mobile
[Termes IGN] télémétrie laser terrestre
[Termes IGN] traitement d'imageRésumé : (auteur) Ongoing innovations in dense multi-view stereo image matching meanwhile allow for 3D data collection using image sequences captured from mobile mapping platforms even in complex and densely built-up areas. However, the extraction of dense and precise 3D point clouds from such street-level imagery presumes high quality georeferencing as a first processing step. While standard direct georeferencing solves this task in open areas, poor GNSS coverage in densely built-up areas and urban canyons frequently prevents sufficient accuracy and reliability. Thus, we use bundle block adjustment, which additionally integrates tie and control point information for precise georeferencing of our multi-camera mobile mapping system. Subsequently, this allows the adaption of a state-of-the-art dense image matching pipeline to provide a suitable 3D representation of the captured urban structures. In addition to the presentation of different processing steps, this paper also provides an evaluation of the achieved image-based 3D capture in a dense urban environment. Numéro de notice : A2016-981 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.82.12.925 En ligne : https://doi.org/10.14358/PERS.82.12.925 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83693
in Photogrammetric Engineering & Remote Sensing, PERS > vol 82 n° 12 (December 2016) . - pp 925 - 933[article]