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Author Carme Julia; Angel Sappa; Felipe Lumbreras; Joan Serrat; Antonio Lopez edit   pdf
url  openurl
  Title An iterative multiresolution scheme for SFM with missing data Type Journal Article
  Year (down) 2009 Publication Journal of Mathematical Imaging and Vision Abbreviated Journal JMIV  
  Volume 34 Issue 3 Pages 240–258  
  Keywords  
  Abstract Several techniques have been proposed for tackling the Structure from Motion problem through factorization in the case of missing data. However, when the percentage of unknown data is high, most of them may not perform as well as expected. Focussing on this problem, an iterative multiresolution scheme, which aims at recovering missing entries in the originally given input matrix, is proposed. Information recovered following a coarse-to-fine strategy is used for filling in the missing entries. The objective is to recover, as much as possible, missing data in the given matrix.
Thus, when a factorization technique is applied to the partially or totally filled in matrix, instead of to the originally given input one, better results will be obtained. An evaluation study about the robustness to missing and noisy data is reported.
Experimental results obtained with synthetic and real video sequences are presented to show the viability of the proposed approach.
 
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ JSL2009a Serial 1163  
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Author Daniel Ponsa; Antonio Lopez edit   pdf
doi  openurl
  Title Variance reduction techniques in particle-based visual contour Tracking Type Journal Article
  Year (down) 2009 Publication Pattern Recognition Abbreviated Journal PR  
  Volume 42 Issue 11 Pages 2372–2391  
  Keywords Contour tracking; Active shape models; Kalman filter; Particle filter; Importance sampling; Unscented particle filter; Rao-Blackwellization; Partitioned sampling  
  Abstract This paper presents a comparative study of three different strategies to improve the performance of particle filters, in the context of visual contour tracking: the unscented particle filter, the Rao-Blackwellized particle filter, and the partitioned sampling technique. The tracking problem analyzed is the joint estimation of the global and local transformation of the outline of a given target, represented following the active shape model approach. The main contributions of the paper are the novel adaptations of the considered techniques on this generic problem, and the quantitative assessment of their performance in extensive experimental work done.  
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  Area Expedition Conference  
  Notes ADAS Approved no  
  Call Number ADAS @ adas @ PoL2009a Serial 1168  
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Author Carme Julia; Angel Sappa; Felipe Lumbreras; Joan Serrat; Antonio Lopez edit   pdf
doi  openurl
  Title Predicting Missing Ratings in Recommender Systems: Adapted Factorization Approach Type Journal Article
  Year (down) 2009 Publication International Journal of Electronic Commerce Abbreviated Journal  
  Volume 14 Issue 1 Pages 89-108  
  Keywords  
  Abstract The paper presents a factorization-based approach to make predictions in recommender systems. These systems are widely used in electronic commerce to help customers find products according to their preferences. Taking into account the customer's ratings of some products available in the system, the recommender system tries to predict the ratings the customer would give to other products in the system. The proposed factorization-based approach uses all the information provided to compute the predicted ratings, in the same way as approaches based on Singular Value Decomposition (SVD). The main advantage of this technique versus SVD-based approaches is that it can deal with missing data. It also has a smaller computational cost. Experimental results with public data sets are provided to show that the proposed adapted factorization approach gives better predicted ratings than a widely used SVD-based approach.  
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  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1086-4415 ISBN Medium  
  Area Expedition Conference  
  Notes ADAS Approved no  
  Call Number ADAS @ adas @ JSL2009b Serial 1237  
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Author Arnau Ramisa; Adriana Tapus; David Aldavert; Ricardo Toledo; Ramon Lopez de Mantaras edit  doi
openurl 
  Title Robust Vision-Based Localization using Combinations of Local Feature Regions Detectors Type Journal Article
  Year (down) 2009 Publication Autonomous Robots Abbreviated Journal AR  
  Volume 27 Issue 4 Pages 373-385  
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  Abstract This paper presents a vision-based approach for mobile robot localization. The model of the environment is topological. The new approach characterizes a place using a signature. This signature consists of a constellation of descriptors computed over different types of local affine covariant regions extracted from an omnidirectional image acquired rotating a standard camera with a pan-tilt unit. This type of representation permits a reliable and distinctive environment modelling. Our objectives were to validate the proposed method in indoor environments and, also, to find out if the combination of complementary local feature region detectors improves the localization versus using a single region detector. Our experimental results show that if false matches are effectively rejected, the combination of different covariant affine region detectors increases notably the performance of the approach by combining the different strengths of the individual detectors. In order to reduce the localization time, two strategies are evaluated: re-ranking the map nodes using a global similarity measure and using standard perspective view field of 45°.
In order to systematically test topological localization methods, another contribution proposed in this work is a novel method to see the degradation in localization performance as the robot moves away from the point where the original signature was acquired. This allows to know the robustness of the proposed signature. In order for this to be effective, it must be done in several, variated, environments that test all the possible situations in which the robot may have to perform localization.
 
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  Series Volume Series Issue Edition  
  ISSN 0929-5593 ISBN Medium  
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  Notes ADAS Approved no  
  Call Number Admin @ si @ RTA2009 Serial 1245  
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Author Carme Julia; Angel Sappa; Felipe Lumbreras; Joan Serrat; Antonio Lopez edit   pdf
doi  openurl
  Title Rank Estimation in 3D Multibody Motion Segmentation Type Journal Article
  Year (down) 2008 Publication Electronic Letters Abbreviated Journal  
  Volume 44 Issue 4 Pages 279-280  
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  Abstract A novel technique for rank estimation in 3D multibody motion segmentation is proposed. It is based on the study of the frequency spectra of moving rigid objects and does not use or assume a prior knowledge of the objects contained in the scene (i.e. number of objects and motion). The significance of rank estimation on multibody motion segmentation results is shown by using two motion segmentation algorithms over both synthetic and real data.  
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ JSL2008a Serial 939  
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Author Joan Serrat; Ferran Diego; Felipe Lumbreras; Jose Manuel Alvarez; Antonio Lopez; C. Elvira edit   pdf
doi  openurl
  Title Dynamic Comparison of Headlights Type Journal Article
  Year (down) 2008 Publication Journal of Automobile Engineering Abbreviated Journal  
  Volume 222 Issue 5 Pages 643–656  
  Keywords video alignment  
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ SDL2008a Serial 958  
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Author Yu Jie; Jaume Amores; N. Sebe; Petia Radeva; Tian Qi edit  openurl
  Title Distance Learning for Similarity Estimation Type Journal
  Year (down) 2008 Publication IEEE Trans. on Pattern Analysis and Machine Intelligence, vol.30(3):451–462 Abbreviated Journal  
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  Notes ADAS;MILAB Approved no  
  Call Number ADAS @ adas @ JAS2008 Serial 961  
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Author Angel Sappa; Fadi Dornaika; Daniel Ponsa; David Geronimo; Antonio Lopez edit   pdf
url  openurl
  Title An Efficient Approach to Onboard Stereo Vision System Pose Estimation Type Journal Article
  Year (down) 2008 Publication IEEE Transactions on Intelligent Transportation Systems Abbreviated Journal TITS  
  Volume 9 Issue 3 Pages 476–490  
  Keywords Camera extrinsic parameter estimation, ground plane estimation, onboard stereo vision system  
  Abstract This paper presents an efficient technique for estimating the pose of an onboard stereo vision system relative to the environment’s dominant surface area, which is supposed to be the road surface. Unlike previous approaches, it can be used either for urban or highway scenarios since it is not based on a specific visual traffic feature extraction but on 3-D raw data points. The whole process is performed in the Euclidean space and consists of two stages. Initially, a compact 2-D representation of the original 3-D data points is computed. Then, a RANdom SAmple Consensus (RANSAC) based least-squares approach is used to fit a plane to the road. Fast RANSAC fitting is obtained by selecting points according to a probability function that takes into account the density of points at a given depth. Finally, stereo camera height and pitch angle are computed related to the fitted road plane. The proposed technique is intended to be used in driverassistance systems for applications such as vehicle or pedestrian detection. Experimental results on urban environments, which are the most challenging scenarios (i.e., flat/uphill/downhill driving, speed bumps, and car’s accelerations), are presented. These results are validated with manually annotated ground truth. Additionally, comparisons with previous works are presented to show the improvements in the central processing unit processing time, as well as in the accuracy of the obtained results.  
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  Publisher IEEE Place of Publication Editor  
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ SDP2008 Serial 1000  
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Author Fadi Dornaika; Angel Sappa edit  openurl
  Title Evaluation of an Appearance-based 3D Face Tracker using Dense 3D Data Type Journal
  Year (down) 2008 Publication Machine Vision and Applications Abbreviated Journal  
  Volume 19 Issue 5-6 Pages 427–441  
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ DoS2008b Serial 1018  
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Author Hugo Berti; Angel Sappa; Osvaldo Agamennoni edit  openurl
  Title Improved Dynamic Window Approach by Using Lyapunov Stability Criteria Type Journal
  Year (down) 2008 Publication Latin American Applied Research Abbreviated Journal  
  Volume 38 Issue 4 Pages 289–298  
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  Notes ADAS Approved no  
  Call Number ADAS @ adas @ BSA2008 Serial 1056  
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