Unsupervised calibrated sonar imaging for seabed observation using hidden Markov random fields

International audienceThis paper deals with seabed imaging issued from sonar systems. Such imaging systems produce images of backscattering (BS) strength relative to physical seabed characteristics. However, these Bs measurements are not only seabed-related but also dependent on the incident angle. Therefore, to enhance the quality of such seabed imaging systems, we develop an unsupervised approach to compensate for these seabed-related angular dependencies. Our approach combines robust estimation and hidden Markov random fields. Results on real data demonstrate the relevance of our approach to improve seabed observation

A goal-driven unsupervised image segmentation method combining graph-based processing and Markov random fields

Image segmentation is the process of partitioning a digital image into a set of homogeneous regions (according to some homogeneity criterion) to facilitate a subsequent higher-level analysis. In this context, the present paper proposes an unsupervised and graph-based method of image segmentation, which is driven by an application goal, namely, the generation of image segments associated with a user-defined and application-specific goal. A graph, together with a random grid of source elements, is defined on top of the input image. From each source satisfying a goal-driven predicate, called seed, a propagation algorithm assigns a cost to each pixel on the basis of similarity and topological connectivity, measuring the degree of association with the reference seed. Then, the set of most significant regions is automatically extracted and used to estimate a statistical model for each region. Finally, the segmentation problem is expressed in a Bayesian framework in terms of probabilistic Markov random field (MRF) graphical modeling. An ad hoc energy function is defined based on parametric models, a seed-specific spatial feature, a background-specific potential, and local-contextual information. This energy function is minimized through graph cuts and, more specifically, the alpha-beta swap algorithm, yielding the final goal-driven segmentation based on the maximum a posteriori (MAP) decision rule. The proposed method does not require deep a priori knowledge (e.g., labelled datasets), as it only requires the choice of a goal-driven predicate and a suited parametric model for the data. In the experimental validation with both magnetic resonance (MR) and synthetic aperture radar (SAR) images, the method demonstrates robustness, versatility, and applicability to different domains, thus allowing for further analyses guided by the generated product

A Q-Ising model application for linear-time image segmentation

A computational method is presented which efficiently segments digital grayscale images by directly applying the Q-state Ising (or Potts) model. Since the Potts model was first proposed in 1952, physicists have studied lattice models to gain deep insights into magnetism and other disordered systems. For some time, researchers have realized that digital images may be modeled in much the same way as these physical systems (i.e., as a square lattice of numerical values). A major drawback in using Potts model methods for image segmentation is that, with conventional methods, it processes in exponential time. Advances have been made via certain approximations to reduce the segmentation process to power-law time. However, in many applications (such as for sonar imagery), real-time processing requires much greater efficiency. This article contains a description of an energy minimization technique that applies four Potts (Q-Ising) models directly to the image and processes in linear time. The result is analogous to partitioning the system into regions of four classes of magnetism. This direct Potts segmentation technique is demonstrated on photographic, medical, and acoustic images.Comment: 7 pages, 8 figures, revtex, uses subfigure.sty. Central European Journal of Physics, in press (2010

Multilayer Markov Random Field Models for Change Detection in Optical Remote Sensing Images

In this paper, we give a comparative study on three Multilayer Markov Random Field (MRF) based solutions proposed for change detection in optical remote sensing images, called Multicue MRF, Conditional Mixed Markov model, and Fusion MRF. Our purposes are twofold. On one hand, we highlight the significance of the focused model family and we set them against various state-of-the-art approaches through a thematic analysis and quantitative tests. We discuss the advantages and drawbacks of class comparison vs. direct approaches, usage of training data, various targeted application fields and different ways of ground truth generation, meantime informing the Reader in which roles the Multilayer MRFs can be efficiently applied. On the other hand we also emphasize the differences between the three focused models at various levels, considering the model structures, feature extraction, layer interpretation, change concept definition, parameter tuning and performance. We provide qualitative and quantitative comparison results using principally a publicly available change detection database which contains aerial image pairs and Ground Truth change masks. We conclude that the discussed models are competitive against alternative state-of-the-art solutions, if one uses them as pre-processing filters in multitemporal optical image analysis. In addition, they cover together a large range of applications, considering the different usage options of the three approaches

From Statistical Detection to Decision Fusion: Detection of Underwater Mines in High Resolution SAS Images

ISBN 978-3-902613-48-6Many approaches have been proposed in underwater mine detection and classification using sonar images. The goal is to evaluate a confidence that a pixel belongs to a sought object or to the seabed. In the following, considering the object characteristics (size, reflectivity), we will always assume that the detected objects are actual mines. We propose a detection method structured as a data fusion system. This type of architecture is a smart and adaptive structure: the addition or removal of parameters is easily taken into account, without any modification of the global structure. The inputs of the proposed system are the parameters extracted from an SAS image (statistical in our case). The outputs of the system are the areas detected as potentially including an object

Markov models in image processing

The aim of this paper is to present some aspects of Markov model based statistical image processing. After a brief review of statistical processing in image segmentation, classical Markov models (fields, chains, and trees) used in image processing are developed. Bayesian methods of segmentation are then described and different general parameter estimation methods are presented. More recent models and processing techniques, such as Pairwise and Triplet Markov models, Dempster-Shafer fusion in a Markov context, and generalized mixture estimation, are then discussed. We conclude with a nonexhaustive desciption of candidate extensions to multidimensional, multisensor, and multiresolution imagery. Connections with general graphical models are also highlighted.L'objet de l'article est de présenter divers aspects des traitements statistiques des images utilisant des modèles de Markov. En choisissant pour cadre la segmentation statistique nous rappelons brièvement la nature et l'intérêt des traitements probabilistes et présentons les modèles de Markov cachés classiques : champs, chaînes, et arbres. Les méthodes bayésiennes de segmentation sont décrites, ainsi que les grandes familles des méthodes d'apprentissage. Quelques modèles ou méthodes de traitements plus récents comme les modèles de Markov Couple et Triplet, la fusion de Dempster-Shafer dans le contexte markovien, ou l'estimation des mélanges généralisés sont également présentés. Nous terminons par une liste non exhaustive des divers prolongements des méthodes et modèles vers l'imagerie multidimensionnelle, multisenseurs, multirésolution. Des liens avec les modèles graphiques généraux sont également brièvement décrits