Search results for "RECONSTRUCTION"
showing 10 items of 784 documents
Evolutionary-based 3D reconstruction using an uncalibrated stereovision system: application of building a panoramic object view
2010
In this paper, we propose an original evolutionary-based method for 3D panoramic reconstruction from an uncalibrated stereovision system (USS). The USS is composed of five cameras located on an arc of a circle around the object to be analyzed. The main originality of this work concerns the process of the calculation of the 3D information. Actually, with our method, 3D coordinates are directly obtained without any prior estimation of the fundamental matrix. The method operates in two steps. Firstly, points of interest are detected in pairs of images acquired by two consecutive cameras of the USS are matched. And secondly, using evolutionary algorithms, we jointly compute the transformed matr…
A Study on Patch-Based Progressive Coding Schemes of Semi-Regular 3D Meshes for Local Wavelet Compression and View-Dependent Transmission
2010
International audience; This paper firstly introduces a wavelet-based segmentation for three-dimensional (3D) Semi-Regular (SR) meshes, as a pre-processing step, in a region-independent progressive coding algorithm. The proposed segmentation process aims at producing homogeneous regions with respect to their frequency amplitudes on the mesh surface, in other words: patches with different degrees of roughness. We have then studied the behavior of the wavelets, obtained during the independent coding of each region, especially close to the patch boundaries. The main contribution of this paper consists in considering three different possible wavelet decompositions, close to the region borders, …
Semantics knowledge management for the 3D architectural reconstruction of building objects
2010
International audience; This paper presents the framework of an ongoing semantics knowledge management practice. The practice combines geometrical analysis of point cloud and semantic rules to detect 3D building objects for the purpose of achieving computational correctness and efficiency. We assume that improvement in the form of well organized classification (CLA) and order (ORD) is a solution. Statically related knowledge is classified as definition, partial knowledge and ambiguous knowledge and formally revealed with transitions between CWA (closed world assumption) and OWA (open world assumption). To achieve the correctness, formalization is proposed for the validation of the rules thr…
Reconstruction et analyse sémantique de chronologies cybercriminelles
2014
International audience; La reconstruction de scénarios est l’une des étapes les plus importantes d’une investigation numérique. Elle permet aux enquêteurs d’avoir une vue des évènements survenus durant un incident. La reconstruction de scénarios est une tâche complexe requérant l’étude d’un très grand nombre d’évènements en raison de l’omniprésence des nouvelles technologies dans notre quotidien. De plus, les conclusions produites se doivent de respecter les critères fixés par la justice. Afin de répondre à ces challenges, nous proposons une nouvelle méthodologie, basée sur une ontologie intégrant les connaissances d’experts des domaines de la criminalistique et de l’ingénierie logicielle, …
De la scène de crime aux connaissances : représentation d'évènements et peuplement d'ontologie appliqués au domaine de la criminalistique informatique
2015
International audience; Avec la démocratisation des technologies, les enquêtes de criminalistique informatique impliquent des volumes de données toujours plus grands et hétérogènes. Pour faciliter le travail des enquêteurs, nos travaux ont pour objectif de reconstruire automatiquement les évènements liés à un incident numérique, tout en respectant les exigences légales. Pour cela, il est nécessaire d'introduire un modèle de représentation de connaissances permettant de structurer les informations recueillies sur une scène de crime dans le but de faciliter l'utilisation de processus d'analyse automatisés. Ce papier propose un état de l'art des modèles de représentations d'évènements pour le …
Reconstruction 3D de scènes dynamiques par segmentation au sens du mouvement
2016
National audience; L'objectif de ce travail est de reconstruire les parties sta-tiques et dynamiques d'une scène 3D à l'aide d'un robot mobile équipé d'un capteur 3D. Cette reconstruction né-cessite la classification des points 3D acquis au cours du temps en point fixe et point mobile indépendamment du dé-placement du robot. Notre méthode de segmentation utilise directement les données 3D et étudie les mouvements des objets dans la scène sans hypothèse préalable. Nous déve-loppons un algorithme complet reconstruisant les parties fixes de la scène à chaque acquisition à l'aide d'un RAN-SAC qui ne requiert que 3 points pour recaler les nuages de points. La méthode a été expérimentée sur de la…
The rapid atmospheric monitoring system of the Pierre Auger Observatory
2012
The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 1017 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shor…
Measurement of the Depth of Maximum of Extensive Air Showers above 10(18) eV
2010
We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10¹⁸ eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106⁺³⁵₋₂₁) g/cm²/decade below 1018.24 ± 0.05 eV and (24 ± 3) g/cm²/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm². The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
2009
Atmospheric parameters, such as pressure (P), temperature (T) and density (ρ ∝ P/T), affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a ∼ 10% seasonal modulation and ∼ 2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of P and ρ. The former affects the longitudinal development of air showers while the latter influences the Molière radius and hence the lateral distribution of the shower particles. The model is val…
Systèmes imageurs 3D pour des applications agricoles : caractérisation de cultures et phénotypage de racines
2016
The development of the concepts of precision agriculture and viticulture since the last three decades has shown the need to use first 2D image acquisition techniques and dedicated image processing. More and more needs concern now 3D images and information. The main ideas of this chapter is thus to present some innovations of the 3D tools and methods in the agronomic domain. This chapter will particularly focus on two main subjects such as the 3D characterization of crop using Shape from Focus or Structure from Motion techniques and the 3D use for root phenotyping using rhizotron system. Results presented show that 3D information allows to better characterize crucial crop morphometric parame…