Visual seabed classification using k-means clustering, CIELAB colors and Gabor-filters

In this article, we discuss visual classification using unsupervised learning combined with methods that originate from human vision to divide the Baltic seabed to the soft and hard areas. Seabed classification plays an important role in an understanding the undersea environment. Seabed can be characterized to be as muddy, rocky or sandy. Mine countermeasures (MCM) missions normally are clearance and/or route finding types and in both of these cases successful detection and classification is strongly connected of seabed type. As our unsupervised learning method, we used k-means clustering. When we filtered our gray-scale seabed picture using Gabor filters, we noticed significant improvement after we segmented filtered image with k-means. We will also show results that we achieved using k-means alone and with Lab colors that are designed to approximate human vision

Influence de l'estimation des paramètres de texture pour la classification de données complexes

National audienceThis paper shows a classification of data based on the theory of belief functions. The complexity of this problem can be seen as two ways. Firstly, data can be imprecise and/or uncertain. Then, it is difficult to choose the right model to represent data. Gaussian model is often used but is limited when data are complex. This model is a particular case of α-stable distributions. Classification is divided into two steps. Learning step allows to modelize data by a mixture of α-stable distributions and Gaussian distributions. Test step allows to classify data with the theory of belief functions and compare the two models. The classification is realized firstly on generated data and then on real data type sonar images

Fast Model-based Automatic Target Recognition Method for Synthetic Aperture Sonar Image

针对基于合成孔径声呐(SAS)图像目标识别的先验模板获取困难、运算复杂度高的问题,该文提出一种基于模型的改进型相关快速识别方法。首先,基于构造凸壳估计目标姿态角,实现目标成像几何关系的估计;其次,提出改进的基于隐藏点移除的目标图像快速生成方法,可实时得到各备选目标对应成像几何关系的仿真图像;进而基于图像相关实现目标图像识别;最后,仿真实验证明了算法的有效性。仿真实验结果表明,相比于常规的直接模板识别方法,该方法识别率高,计算速度快。A modified model-based method is proposed to obtain sufficient prior templates and reduce the computational complexity on Synthetic Aperture Sonar(SAS) automatic target recognition.First, a quick method based on build convex hull is proposed to estimate the target pose quickly as well as the SAS imaging geometry for the specified target.Second, an improved method based on Hidden Point Removal(HPR) algorithm is proposed to obtain the target SAS simulation image effectively.Accordingly, the target recognition is realized by the correlation between the test image and the simulated image.Finally, the effectiveness of the proposed method is verified by the simulation experiment.It is shown that the proposed method can achieve higher computational efficiency than the conventional direct templet-based method, but remain the same high recognition rate.国家自然科学基金(61271391;41176032;41376040)资助课

Automatic Food Intake Assessment Using Camera Phones

Obesity is becoming an epidemic phenomenon in most developed countries. The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended. It is essential to monitor everyday food intake for obesity prevention and management. Existing dietary assessment methods usually require manually recording and recall of food types and portions. Accuracy of the results largely relies on many uncertain factors such as user\u27s memory, food knowledge, and portion estimations. As a result, the accuracy is often compromised. Accurate and convenient dietary assessment methods are still blank and needed in both population and research societies. In this thesis, an automatic food intake assessment method using cameras, inertial measurement units (IMUs) on smart phones was developed to help people foster a healthy life style. With this method, users use their smart phones before and after a meal to capture images or videos around the meal. The smart phone will recognize food items and calculate the volume of the food consumed and provide the results to users. The technical objective is to explore the feasibility of image based food recognition and image based volume estimation. This thesis comprises five publications that address four specific goals of this work: (1) to develop a prototype system with existing methods to review the literature methods, find their drawbacks and explore the feasibility to develop novel methods; (2) based on the prototype system, to investigate new food classification methods to improve the recognition accuracy to a field application level; (3) to design indexing methods for large-scale image database to facilitate the development of new food image recognition and retrieval algorithms; (4) to develop novel convenient and accurate food volume estimation methods using only smart phones with cameras and IMUs. A prototype system was implemented to review existing methods. Image feature detector and descriptor were developed and a nearest neighbor classifier were implemented to classify food items. A reedit card marker method was introduced for metric scale 3D reconstruction and volume calculation. To increase recognition accuracy, novel multi-view food recognition algorithms were developed to recognize regular shape food items. To further increase the accuracy and make the algorithm applicable to arbitrary food items, new food features, new classifiers were designed. The efficiency of the algorithm was increased by means of developing novel image indexing method in large-scale image database. Finally, the volume calculation was enhanced through reducing the marker and introducing IMUs. Sensor fusion technique to combine measurements from cameras and IMUs were explored to infer the metric scale of the 3D model as well as reduce noises from these sensors

Distributions alpha-stable pour la caractérisation de phénomènes aléatoires observés par des capteurs placés dans un environnement maritime

Le travail réalisé dans le cadre de cette thèse a pour but de caractériser des signaux aléatoires, rencontrés dans le domaine aérien et sous-marin, en s appuyant sur une approche statistique. En traitement du signal, l'analyse statistique a longtemps été fondée sous l'hypothèse de Gaussianité des données. Cependant, ce modèle n'est plus valide dès lors que la densité de probabilité des données se caractérise par des phénomènes de queues lourdes et d'asymétrie. Une famille de lois est particulièrement adaptée pour représenter de tels phénomènes : les distributions a-stables. Dans un premier temps, les distributions a-stables ont été présentées et utilisées pour estimer des données synthétiques et réelles, issues d'un sondeur monofaisceau, dans une stratégie de classification de fonds marins. La classification est réalisée à partir de la théorie des fonctions de croyance, permettant ainsi de prendre en compte l'imprécision et l'incertitude liées aux données et à l'estimation de celles-ci. Les résultats obtenus ont été comparés à un classifieur Bayésien. Dans un second temps, dans le contexte de la surveillance maritime, une approche statistique à partir des distributions a-stables a été réalisée afin de caractériser les échos indésirables réfléchis par la surface maritime, appelés aussi fouillis de mer, où la surface est observée en configuration bistatique. La surface maritime a d'abord été générée à partir du spectre d'Elfouhaily puis la Surface Équivalente Radar (SER) de celle-ci a été déterminée à partir de l'Optique Physique (OP). Les distributions de Weibull et ont été utilisées et comparées au modèle a-stable. La validité de chaque modèle a été étudiée à partir d'un test de Kolmogorov-Smirnov.The purpose of this thesis is to characterize random signals, observed in air and underwater context, by using a statistical approach. In signal processing, the hypothesis of Gaussian model is often used for a statistical study. However, the Gaussian model is not valid when the probability density function of data are characterized by heavy-tailed and skewness phenomena. A family of laws can fit these phenomena: the a-stable distributions. Firstly, the a-stable distribution have been used to estimate generated and real data, extracted from a mono-beam echo-sounder, for seabed sediments classification. The classification is made by using the theory of belief functions, which can take into account the imprecision and uncertainty of data and theirs estimations. The results have been compared to a Bayesian approach. Secondly, in a context a marine surveillance, a statistical study from the a-stable distribution has been made to characterize undesirable echo reflected by a sea surface, called sea clutter, where the sea surface is considered in a bistatic configuration. The sea surface has been firstly generated by the Elfouhaily sea spectrum and the Radar Cross Section (RCS) of the sea surface has been computed by the Physical Optics (PO). The Weibull and distributions have been used and the results compared to the a-stable model. The validity of each model has been evaluated by a Kolmogorov-Smirnov test.BREST-SCD-Bib. electronique (290199901) / SudocSudocFranceF