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Theses

Construction de modèles 3D à partir de données vidéo fisheye : application à la localisation en milieu urbain

Abstract : This research deals with 3D modelling from an embedded fisheye vision system, used for a GNSS application as part of CAPLOC project. Satellite signal propagation in urban area implies reflections on structures, impairing localisation’s accuracy and availability. The project purpose is (1) to define an omnidirectional vision system able to provide information on urban 3D structure and (2) to demonstrate that it allows to improve localisation.This thesis addresses problems of (1) self-calibration, (2) matching between images, (3) 3D reconstruction ; each algorithm is assessed on computer-generated and real images. Moreover, it describes a way to correct GNSS signals reflections from a 3D point cloud to improve positioning. We propose and evaluate two systems based on state-of-the-art methods. First one is a stereoscopic system made of two sky facing fisheye cameras. Second one is the adaptation of the former to a single camera.Calibration is handled by a two-steps process: the 9-point algorithm fitted to “equisolid” model coupled with a RANSAC, followed by a Levenberg-Marquardt optimisation refinement. We focused on the way to apply the method for optimal and repeatable performances. It is a crucial point for a system composed of only one camera because the pose must be estimated for every new image.Stereo matches are obtained for every pixel by dynamic programming using a 3D graph. Matching is done along conjugated epipolar curves projected in a suitable manner on each image. A distinctive feature is that distortions are not rectified in order to neither degrade visual content nor to decrease accuracy. In the binocular case it is possible to estimate full-scale coordinates.In the monocular case, we do it by adding odometer information. Local clouds can be wedged in SfM to form a global cloud.The end application is the usage of the 3D cloud to improve GNSS localisation. It is possible to estimate and consider a signal pseudodistance error after multiple reflections in order to increase positioning accuracy. Reflecting surfaces are modelled thanks to plane and buildings trace fitting. The method is evaluated on fixed image pairs, georeferenced by a low-cost receiver and a GPS RTK receiver (ground truth). Study results show the localisation improvement ability in urban environment.
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https://tel.archives-ouvertes.fr/tel-01417996
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Submitted on : Friday, December 16, 2016 - 11:36:06 AM
Last modification on : Friday, July 17, 2020 - 5:09:00 PM
Long-term archiving on: : Tuesday, March 21, 2017 - 6:02:12 AM

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  • HAL Id : tel-01417996, version 1

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Julien Moreau. Construction de modèles 3D à partir de données vidéo fisheye : application à la localisation en milieu urbain. Vision par ordinateur et reconnaissance de formes [cs.CV]. Université de Technologie de Belfort-Montbeliard, 2016. Français. ⟨NNT : 2016BELF0290⟩. ⟨tel-01417996⟩

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