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Submapping SLAM based on acoustic data from a 6-DOF AUV

IFAC Proceedings Volumes 2010年第20期43卷 16-21页

作者： Josep Aulinas Chee Sing Lee Joaquim Salvi Yvan R. Petillot Computer Vision and Robotics group (ViCoRob) University of Girona 17071 Girona Spain Oceans Systems Lab School of EPS Heriot-Watt University EH144AS Edinburgh United Kindgom

Autonomous Underwater Vehicles (AUVs) need positioning systems besides the Global Positioning System (GPS), since GPS does not work in underwater scenarios. Possible solutions are the Simultaneous Localization and Mapping (SLAM) algorithms. SLAM algorithms aim to build a map while simultaneously localizing the vehicle within this map. However, they offer limited performance when faced with large scale scenarios. For instance, they do not create consistent maps for large areas, mainly because uncertainties increase with the scale of the scenario. In addition, the computational cost increases with the map size. The use of local maps reduces computational cost and improves map consistency. Following this idea, in this paper we propose a new SLAM approach that uses independent local maps together with a global level stochastic map. The global level contains the relative transformations between local maps. These local maps are updated once a new loop is detected. Local maps that are sharing a high number of features are updated through fusion, maintaining the correlation between landmarks and vehicle. Experimental results on real data obtained from the REMUS-100 AUV show that our approach is able to obtain large map areas consistently.

关键词： Autnonomous vehicles robotics navigation

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SLAM based Selective Submap Joining for the Victoria Park Dataset

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IFAC Proceedings Volumes 2010年第16期43卷 557-562页

作者： Josep Aulinas Xavier Lladó Joaquim Salvi Yvan R. Petillot Computer Vision and Robotics group (ViCoRob) University of Girona Girona 17071 Spain Ocean Systems Lab Heriot Watt University Edinburgh EH14 4AS United Kingdom

One of the main drawbacks of current SLAM algorithms is that they do not result in consistent maps of large areas, mainly because the uncertainties increase with the scenario. In addition, as the map size grows the computational costs increase, making SLAM solutions unsuitable for on-line applications. The use of local maps has been demonstrated to be useful in these situations, reducing computational cost and improving map consistency. Following this idea, this paper proposes a technique based on using independent local maps together with a global stochastic map. The global level contains the relative transformations between local maps, which are updated once a new loop is detected. In addition, the information within the local maps is also corrected. Thus, maps sharing a high number of features are updated through fusion and the correlation between landmarks and vehicle is maintained. Results on synthetic data and on the Victoria Park Dataset show that our approach is able to consistently map large areas and the computational costs are lower.

关键词： Localization mapping Extended Kalman Filter data association mobile robots

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Robust Color Image Segmentation through Tensor Voting

Robust Color Image Segmentation through Tensor Voting

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International Conference on Pattern Recognition

作者： Rodrigo Moreno Miguel Angel Garcia Domenec Puig Intelligent Robotics and Computer Vision Group Department of Computer Science and Mathematics Rovira i Virgili University Tarragona Spain Department of Informatics Engineering Autonomous University of Madrid Madrid Spain

ISBN: (纸本)9781424475421

This paper presents a new method for robust color image segmentation based on tensor voting, a robust perceptual grouping technique used to extract salient information from noisy data. First, an adaptation of tensor voting to both image denoising and robust edge detection is applied. Second, pixels in the filtered image are classified into likely-homogeneous and likely-inhomogeneous by means of the edginess maps generated in the first step. Third, the likely-homosgeneous pixels are segmented through an efficient graph-based segmenter. Finally, a modified version of the same graph-based segmenter is applied to the likely-inhomogeneous pixels in order to obtain the final segmentation. Experiments show that the proposed algorithm has a better performance than the state-of-the-art.

关键词： Pixel Image segmentation Tensile stress Robustness Image color analysis Image edge detection Noise measurement

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On Adapting Pixel-based Classification to Unsupervised Texture Segmentation

On Adapting Pixel-based Classification to Unsupervised Textu...

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International Conference on Pattern Recognition

作者： Jaime Melendez Domenec Puig Miguel Angel Garcia Intelligent Robotics and Computer Vision Group Department of Computer Science and Mathematics Rovira i Virgili University Tarragona Spain Department of Informatics Engineering Autonomous University of Madrid Madrid Spain

ISBN: (纸本)9781424475421

An inherent problem of unsupervised texture segmentation is the absence of previous knowledge regarding the texture patterns present in the images to be segmented. A new efficient methodology for unsupervised image segmentation based on texture is proposed. It takes advantage of a supervised pixel-based texture classifier trained with feature vectors associated with a set of texture patterns initially extracted through a clustering algorithm. Therefore, the final segmentation is achieved by classifying each image pixel into one of the patterns obtained after the previous clustering process. Multi-sized evaluation windows following a top-down approach are applied during pixel classification in order to improve accuracy. The proposed technique has been experimentally validated on MeasTex, VisTex and Brodatz compositions, as well as on complex ground and aerial outdoor images. Comparisons with state-of the-art unsupervised texture segmenters are also provided.

关键词： Image segmentation Pixel Clustering algorithms Accuracy Feature extraction Classification algorithms Image edge detection

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Elastic modulus imaging using optical flow and image registration

Elastic modulus imaging using optical flow and image registr...

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IEEE International Conference on Image Processing

作者： Robert Martí Alison Noble Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Spain Biomedical Image Analysis Laboratory Institute of Biomedical Engineering University of Oxford UK

Elastography, the imaging technique for estimating the elastic tissue properties, or more specifically elastic modulus imaging, are becoming important diagnosis tools in computer aided diagnosis system, specially focusing on ultrasound and MRI images. This technique still presents unsolved challenges in the analysis of deformations in sequences of images. The aim of this paper is twofold: to evaluate the applicability of the deformation field obtained by state of the art optical flow and image registration algorithms for elastic modulus imaging and to quantitatively evaluate two different methods for estimation of the elastic modulus distribution. Results show that optical-flow methods provide a slightly better reconstruction and that the reconstruction has been shown to be more accurate using the method proposed by Sumi et al.

关键词： Image reconstruction Optical imaging Strain Young's modulus Image registration Lesions

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Augmented reality approach for paper map visualization

Augmented reality approach for paper map visualization

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International Conference on Communication and Computational Intelligence (INCOCCI)

作者： C Adithya K Kowsik D Namrata V S Nageli Sangeeta Shrivastava S Rakshit Department of Information Science B. M. Sreenivasaiah College of Engineering Bangalore India Computer Vision Group Center for Artificial Intelligence and Robotics Bangalore India

Paper map visualization is good value proposition, even in the `everything is digital' world, because of the huge information density and ease of use at any remote or mobile location, especially in the military context. Completely doing away with the paper map brings in a discomfort factor for the military user. In this paper, we present a paper map data visualization solution that augments the information from the digital world onto a spread of a paper map. Augmented Reality techniques are used to enhance paper maps digitally resulting in a 3D visualization space with some interactions. The dynamic information of the terrain, placing virtual objects and interaction are features of the digital world that are superimposed onto a paper map. We have used ARToolkit marker tracking based approach and a see through Head Mounted Device for implementation. The digital elevation data in VRML format is split into smaller bits before rendering. The rendering is done after culling the relevant part of the terrain data and the same is popped up in stereo for enhanced visualization. The user can place virtual objects using markers. The distance between markers (user and reference) is calculated and is used for interactive features. The interaction options are load/select, slice/split and latch/freeze. We have achieved better performance by loading only the region of interest and not the complete terrain. The paper also illustrates the basic hardware set-up required for implementation.

关键词： Augmented reality Data visualization Cameras Three dimensional displays Rendering (computer graphics) Solid modeling Training

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Feature based slam using side-scan salient objects

Feature based slam using side-scan salient objects

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OCEANS

作者： Josep Aulinas Xavier Lladó Joaquim Salvi Yvan R. Petillot Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Girona Spain Oceans Systems Laboratory School of Engineering and Physical Sciences Heriot-Watt University Edinburgh UK

Different underwater vehicles have been developed in order to explore underwater regions, specially those of difficult access for humans. Autonomous Underwater Vehicles (AUVs) are equipped with on-board sensors, which provide valuable information about the vehicle state and the environment. This information is used to build an approximate map of the area and estimate the position of the vehicle within this map. This is the so called Simultaneous Localization and Mapping (SLAM) problem. In this paper we propose a feature based submapping SLAM approach which uses side-scan salient objects as landmarks for the map building process. The detection of salient features in this environment is a complex task, since sonar images are noisy. We present in this paper an algorithm based on a set of image preprocessing steps and the use of a boosted cascade of Haar-like features to perform the automatic detection in side-scan images. Our experimental results show that the method produces consistent maps, while the vehicle is precisely localized.

关键词： Simultaneous localization and mapping Vehicles Feature extraction Sonar detection Object detection Sonar navigation

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Multimodal prostate registration using thin-plate splines from automatic correspondences

Multimodal prostate registration using thin-plate splines fr...

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International Conference on Digital Image Computing: Techniques and Applications, DICTA 2010

作者： Mitra, Jhimli Oliver, Arnau Martí, Robert Lladó, Xavier Vilanova, Joan C. Meriaudeau, Fabrice Computer Vision and Robotics Group University of Girona Campus Montilivi Av. Lluís Santaló s/n 17071 Girona Spain Clinica Girona Calle Joan Maragall 26 17002 Girona Spain Laboratoire Le2I - UMR CNRS 5158 Université de Bourgogne 12 Rue de la Fonderie 71200 Le Creusot France

ISBN: (纸本)9780769542713

Registration is an important step during prostate biopsy with interventional Ultrasound (US) to project the Magnetic Resonance (MR) information of the corresponding slice of a pre-acquired MR volume of the same patient. This paper presents a method of deformable registration between US and MR prostate modalities using Thin-Plate Splines (TPS). The use of radial-basis functions such as splines is a typical approach for deformable registration wherein, TPS are more computationally efficient than B-splines. However, registration with TPS employs strategic choice of correspondence points in the moving and reference images and therefore, has been rarely used by researchers for prostate registration. Aiming to deal with this issue, a novel method to automatically choose correspondence points (control points) based on the prostate geometry is presented in this paper. Shepard's interpolation is used with the TPS in order to deal with the interpolation artifacts produced by reverse TPS transform. To evaluate the accuracy of our correspondence generation method, two intuitive geometric methods for prostate contour sampling are also implemented. Our registration results are validated using 4 patient datasets obtaining an average DSC of 0.97 ± 0.01. © 2010 IEEE.

关键词： Magnetic resonance

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Prostate segmentation with texture enhanced active appearance model

Prostate segmentation with texture enhanced active appearanc...

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International Conference on Signal Image Technology and Internet Based Systems

作者： Ghose, Soumya Oliver, Arnau Martí, Robert Lladó, Xavier Freixenet, Jordi Vilanova, Joan C. Meriaudeau, Fabrice Laboratoire Le2I UMR CNRS 5158 Université de Bourgogne 12 Rue de la Fonderie 71200 Le Creusot France Computer Vision and Robotics Group University of Girona Campus Montilivi Av. Lluís Santaló s/n 17071 Girona Spain Clinica Girona Calle Joan Maragall 26 17002 Girona Spain

ISBN: (纸本)9780769543192

Prostate contour segmented from Trans Rectal Ultra Sound (TRUS) and Magnetic Resonance (MR) images could improve inter-modality registration accuracy and reduce computational complexity of the procedure. However, prostate segmentation in each of these modalities is a challenging task in presence of imaging artifacts, intensity heterogeneities, and large inter patient shape variabilities of the *** propose to use Haar wavelet approximation coefficients to extract texture features of the prostate region in both modalities to guide a deformable parametric model to segment the prostate in a multi-resolution framework. Principal Component Analysis (PCA) of the shape and texture information of the prostate region obtained from the training data aids contour propagation of the deformable parametric model. Prior knowledge of the optimization space is utilized for optimal segmentation of the prostate. Our method achieves a mean Dice Similarity Coefficient (DSC) value of 0.95±0.01, with mean segmentation time of 0.72±0.05 seconds in a leave-one-out validation framework with 25 TRUS images grabbed from a video sequence. DSC value of 0.88 ± 0.06 with a mean segmentation time of 0.81 ± 0.02 seconds was recorded for MR images when validated with 15 central slice images of 15 datasets from the MICCAI prostate segmentation challenge 2009. Our proposed method performs computationally efficient accurate multi-modal prostate segmentation in presence of intensity heterogeneities and imaging artifacts. © 2010 IEEE.

关键词： Magnetic resonance

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A Thin-Plate Spline based multimodal prostate registration with optimal correspondences

A Thin-Plate Spline based multimodal prostate registration w...

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International Conference on Signal Image Technology and Internet Based Systems

作者： Mitra, Jhimli Oliver, Arnau Martí, Robert Lladó, Xavier Vilanova, Joan C. Meriaudeau, Fabrice Laboratoire Le2I UMR CNRS 5158 Université de Bourgogne 12 Rue de la Fonderie 71200 Le Creusot France Computer Vision and Robotics Group University of Girona Campus Montilivi Av. Lluís Santaló s/n 17071 Girona Spain Clinica Girona Calle Joan Maragall 26 17002 Girona Spain

ISBN: (纸本)9780769543192

Accurate extraction of prostate biopsy samples during Transectal Ultra Sound (TRUS) guided prostate biopsy is facilitated with the registration of pre-acquired Magnetic Resonance (MR) images with the Ultrasound (US) images. This paper proposes a novel method of generating optimal correspondences to register the MR and US images using Thin-Plate Splines (TPS) transformation. The correspondence generation method exploits the prostate shape geometry in both the modalities and is fully automatic. Normalized Mutual Information (NMI) is employed for the quantitative determination of optimal number of correspondences in terms of maximization of registration similarity. Qualitative registration results, that conform to the NMI measures are also shown for different numbers of correspondences. Shepard's interpolation method is used with the TPS in order to deal with the interpolation error of backward TPS transformation. The accuracy of our method of correspondence generation is qualitatively evaluated in comparison with two intuitive geometric contour sampling methods. An average Dice Similarity Coefficient (DSC) value of 0.97 ± 0.01 for 4 patient datasets is obtained for the TPS registration using our novel method of correspondences. © 2010 IEEE.

关键词： Magnetic resonance

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