Sonar Data Simulation

International audienceTherefore, the proposed chapter will first present such diversity in order to clearly understand the crucial needs for simulation and the involved consequences. Moreover, our goal is to keep all these descriptions along with existing methods and possibilities, within a common frame. Thus, responding to the presented needs,we have developed a framework for simulators allowing both underwater scene design and computational simulation engine choices. More precisely, this generic framework provides the reader with a common and simple software system in which various sensors, environments and computational engines can be plugged in. Subsequent sections of the chapter will then describe this common representation with all the phenomena to be considered and the problems to be answered in order to produce realistic simulated sonar data. We will introduce ray and tube engines in order to collect exhaustively all the backscattered acoustic waves resulting from scene interactions with the transmitting acoustic wave. This allows mainly imaging sonars to be simulated (sidescan, front-looking sonars), as only energy is considered for these engines. Another engine will then be introduced to allow the simulation of a full signal (both intensity and phase). The new resulting local signal/scene interactions will be explained and results shown through the simulation of an interferometry system. Finally, the chapter objectives are twofold: presenting a generic framework for simulation while dealing with actual, specific sensors features and chosen acoustic models

Accueil des étudiants non-francophones pour une intégration linguistique, interculturelle et scientifique

National audienceAccueil des étudiants non-francophones pour une intégration linguistique, interculturelle et scientifique. Ouverture de cette formation à d'autres Grandes Ecoles et Universités. Actuellement on constate une forte augmentation de la proportion d'étudiants étrangers non francophones sur les bancs de nos universités et écoles. Si nos institutions veillent à la qualité de l'enseignement scientifique, il semble qu'elles aient du mal à prendre en compte ce nouveau facteur. De plus dans une logique de marché, l'enseignement devient une quantité, un savoir faire monnayable. De plus la tendance est à la globalisation des enseignements, c'est à dire à l'opposé de la prise en compte de cette nouvelle caractéristique de nos étudiants non francophones. Ils sont d'origines diverses et de langues diverses. L'anglais n'est pas une solution pour la communication entre individus car il est soit inconnu soit mal maitrisé. Tout ce contexte favorise le clivage et le renfermement sur les communautés. Pour éviter cela, améliorer la qualité de l'enseignement par le biais d'un semestre d'harmonisation et d'adaptation a été mis en place à travers la définition de trois outils pédagogiques que sont le MAI (module d'adaptation interculturel), le MAS (module d'adaptation scientifique) et le FLCS (français langue de communication scientifique) avec comme charnière centrale la langue française. Le MAI permet de valoriser la diversité d'origines de nos étudiants en présentant leurs pays coutumes, spécificités dans la langue française aux autres étudiants. Le MAS est un projet d'élèves organisé autour d'un jeu de rôle qui favorise le travail en groupe l'échange et l'autonomie sur un arrière plan de défi technique. Enfin le FLCS est une analyse de préparation des étudiants aux cours qu'ils vont suivre sous la tutelle des enseignants de langue ; le département de langue devenant ainsi à part entière un élément de la pédagogie scientifique. Cette initiative SAH devient un outil supplémentaire aux MOOC, Moodle de l'enseignement dans notre enseignement supérieur

Statistical modeling of interferometric signals in underwater applications

International audienceCurrent sonar and radar applications use interferometry to estimate the arrival angles of backscattered signals at time-sampling rate. This direction-finding method is based on a phase-difference measurement between two close receivers. To quantify the associated bathymetric measurement quality, it is necessary to model thestatistical properties of the interferometric-phase estimator. Thus, this paper investigates the received signal structure, decomposing it into three different terms: a part correlated on the two receivers, an uncorrelated part and an ambient noise term. This paper shows that the uncorrelated part and the noise term can be merged into a unique, random term damaging the measurement performance. Concerning the correlated part, its modulus can be modeled either as a random or a constant variable according to the type of underwater acoustic application. The existence of these two statistical behaviors is verified on real data collected from different underwater scenarios such as a horizontal emitter-receiver communication and a bathymetric seafloor survey. The physical understood of the resulting phase distributions makes it possible to model and simulate the interferometric-signal variance (associated with the measurement accuracy) according to the underwater applications through simple hypotheses

Reconstruction bathymétrique sonar en présence de trajets multiples et de bruit impulsif

National audienceCet article propose une méthode de poursuite de l'angle d'arrivée de l'écho principal rétrodiffusé par le fond marin pour la reconstruction bathymétrique. Cette méthode présente certains avantages par rapport aux techniques classiques d'estimation de l'angle d'arrivée et permet en particulier de régulariser la trajectoire de l'angle estimé et ainsi réduire le niveau d'interférence causé par les échos secondaires

Simulation on large scale of acoustic signals for array processing

International audienceDue to operational constraints for underwater data acquisition, simulating realistic sonar data, like images, swath bathymetry profiles or interferometric signals, is crucial for tuning detection and classification algorithms according to sensors settings, sea-bottom nature and topography. Moreover, the robustness of any performance estimation or prediction can be greatly enhanced, as soon as such a simulation tool provides a modular and flexible underwater world representation (multiple sensors, environments and acquisition conditions). For signal and array processing, it is essential not only to generate the signal energy backscattered by a resolution cell, but also to produce a phase information that conveys its theoretical statistical properties. To this end, this paper proposes a Brownian motion-based approach to generate complex Gaussian signals from the contribution of a set of extended single scatterers inside a resolution cell. The resulting process preserves the conservation of energy when integrating on surfaces, as well as the decorrelation between different areas of the sea bottom, and the right interference between two sensors for interferometric applications

Advanced interferometric techniques for high resolution bathymetry

International audienceCurrent high-resolution side scan and multibeam sonars produce very large data sets. However, conventional interferometry-based bathymetry algorithms underestimate the potential information of such soundings, generally because they use small baselines to avoid phase ambiguity. Moreover, these algorithms limit the triangulation capabilities of multibeam echosounders to the detection of one sample per beam, i.e., the zero-phase instant. In this paper we argue that the correlation between signals plays a very important role in the exploration of a remotely observed scene. In the case of multibeam sonars, capabilities can be improved by using the interferometric signal as a continuous quantity. This allows consideration of many more useful soundings per beam and enriches understanding of the environment. To this end, continuous interferometry detection is compared here, from a statistical perspective, first with conventional interferometry-based algorithms and then with high-resolution methods, such as the Multiple Signal Classification (MUSIC) algorithm. We demonstrate that a well-designed interferometry algorithm based on a coherence error model and an optimal array configuration permits a reduction in the number of beam formings (and therefore the computational cost) and an improvement in target detection (such as ship mooring cables or masts). A possible interferometry processing algorithm based on the complex correlation between received signals is tested on both sidescan sonars and multibeam echosounders and shows promising results for detection of small in-water targets

Super-resolution-based snake model—an unsupervised method for large-scale building extraction using airborne LiDAR Data and optical image

Automatic extraction of buildings in urban and residential scenes has become a subject of growing interest in the domain of photogrammetry and remote sensing, particularly since the mid-1990s. Active contour model, colloquially known as snake model, has been studied to extract buildings from aerial and satellite imagery. However, this task is still very challenging due to the complexity of building size, shape, and its surrounding environment. This complexity leads to a major obstacle for carrying out a reliable large-scale building extraction, since the involved prior information and assumptions on building such as shape, size, and color cannot be generalized over large areas. This paper presents an efficient snake model to overcome such a challenge, called Super-Resolution-based Snake Model (SRSM). The SRSM operates on high-resolution Light Detection and Ranging (LiDAR)-based elevation images—called z-images—generated by a super-resolution process applied to LiDAR data. The involved balloon force model is also improved to shrink or inflate adaptively, instead of inflating continuously. This method is applicable for a large scale such as city scale and even larger, while having a high level of automation and not requiring any prior knowledge nor training data from the urban scenes (hence unsupervised). It achieves high overall accuracy when tested on various datasets. For instance, the proposed SRSM yields an average area-based Quality of 86.57% and object-based Quality of 81.60% on the ISPRS Vaihingen benchmark datasets. Compared to other methods using this benchmark dataset, this level of accuracy is highly desirable even for a supervised method. Similarly desirable outcomes are obtained when carrying out the proposed SRSM on the whole City of Quebec (total area of 656 km2), yielding an area-based Quality of 62.37% and an object-based Quality of 63.21%

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

Side scan sonar and interferometric noise

International audienceThis paper concerns the description of different noise sources encountered as well as the impact of each of these sources through the sonar interferometric data acquisition. In fact, these noise sources can generally be classed into two categories: a. environmental noise category (variable celerity, parasite echoes, sonar motion, etc,), and b. interferometric process related noise (decorrelation baseline, decorrelation of wave train, propagation). In this study, each noise source (considered separately) is first modeled in terms of signal to noise ratio (SNR) as a function of range. This modeling is conducted analytically as well as using computer simulations. The obtained information is, then, converted in order to obtain an altitude error precision scheme. Obtained results clearly show that these different noise sources have not the same altitude error impact. In fact, the decorrelation of wave-train and the parasite echoes are shown to be the most significant. Finally, an error data fusion process is studied in order to evaluate the altitude precision degradation through the integration of several noise phenomena. The main conclusion of this paper concerns the theoretical interest of the conducted approach in terms of the obtained results as well as in order to reduce the impact of these noise sources through the physical and the analytical comprehension of the data acquisition process

Déconvolution bathymétrique d'images sonar latéral par des méthodes interférométriques et de traitement de l'image

Ces travaux de thse concernent l'tude d'un sonar latral interfromtrique. Le sonar latral dlivre des images haute dfinition des fonds marins, mais la reprsentation de la ralit est biaise en raison du systme d'acquisition. L'option interfromtrique permet de calculer l'altitude de chaque point de l'image, ce qui permet de reconstruire une image tri-dimensionnelle et conforme la zone explore. La mesure de cette altitude repose sur une mesure de retard entre deux antennes distinctes, du trajet retour de l'onde sonore. Ce retard est constitu de partie le retard fin ou phase interfromtrique et le retard grossier ou nombre de priodes entires de la porteuse Dans un premier temps une tude des caractristiques de la phase interfromtrique est effectue, afin de permettre de cerner les diffrents phnomnes polluant le signal et de permettre une prdiction de performances sonar. La troisime partie s'intresse au retard grossier qui est estim par la mthode du vernier. Une tude des configurations d'antennes permet d'optimiser la conception de l'interfromtre. Enfin, la dernire partie, en s'appuyant sur les lments scientifiques dvelopps dans les deux premires parties, propose une technique de rduction des erreurs des ambiguits de phase conjugue un filtrage du signal interfromtrique par ondelettesRENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF