Browsing by Subject "Tracking (position)"
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Item Open Access Camera-based virtual environment interaction on mobile devices(Springer, 2006-11) Çapin, Tolga; Haro, A.; Setlur, V.; Wilkinson, S.Mobile virtual environments, with real-time 3D and 2D graphics, are now possible on smart phone and other camera-enabled devices. Using computer vision, the camera sensor can be treated as an input modality in applications by analyzing the incoming live video. We present our tracking algorithm and several mobile virtual environment and gaming prototypes including: a 3D first person shooter, a 2D puzzle game and a simple action game. Camera-based interaction provides a user experience that is not possible through traditional means, and maximizes the use of the limited display size. © Springer-Verlag Berlin Heidelberg 2006.Item Open Access Cepstrum based method for moving shadow detection in video(Springer, 2010-09) Cogun, Fuat; Çetin, A. EnisMoving shadows constitute problems in various applications such as image segmentation and object tracking. Main cause of these problems is the misclassification of the shadow pixels as target pixels. Therefore, the use of an accurate and reliable shadow detection method is essential to realize intelligent video processing applications. In this paper, the cepstrum based method for moving shadow detection is presented. The proposed method is tested on outdoor and indoor video sequences using well-known benchmark test sets. To show the improvements over previous approaches, quantitative metrics are introduced and comparisons based on these metrics are made. © 2011 Springer Science+Business Media B.V.Item Open Access A discussion on homography between stationary multi-camera systems and the soccer field model(IEEE, 2012) Baysal, Sermetcan; Duygulu, Pınar; Kayalar, CerenComputer vision based athlete tracking systems use different methods to segment players from the background and then track them automatically throughout the video. It is insufficient to know a player's position on the image plane if we want to extract performance analysis of the player. Furthermore, image plane coordinates need to be transformed to real world coordinates representing the position of the player on the field. Knowing that the soccer field is planar, the mapping between the world coordinate system and the image coordinate system can be described by a planar homography. In this paper, we provide a discussion on homography calculations between a three-camera player tracking system and the real world soccer field model. © 2012 IEEE.Item Open Access A face tracking algorithm for user interaction in mobile devices(IEEE, 2009-09) Bülbül, Abdullah; Çipiloğlu, Zeynep; Çapin, TolgaA new face tracking algorithm, and a human-computer interaction technique based on this algorithm, are proposed for use on mobile devices. The face tracking algorithm considers the limitations of mobile use case - constrained computational resources and varying environmental conditions. The solution is based on color comparisons and works on images gathered from the front camera of a device. The face tracking system generates 2D face position as an output that can be used for controlling different applications. Two of such applications are also presented in this work; the first example uses face position to determine the viewpoint, and the second example enables an intuitive way of browsing large images. © 2009 IEEE.Item Open Access Ground-nesting insects could use visual tracking for monitoring nest position during learning flights(Springer Verlag, 2014-07) Samet, Nermin; Zeil, J.; Mair, E.; Boeddeker, N.; Stürzl, W.Ants, bees and wasps are central place foragers. They leave their nests to forage and routinely return to their home-base. Most are guided by memories of the visual panorama and the visual appearance of the local nest environment when pinpointing their nest. These memories are acquired during highly structured learning walks or flights that are performed when leaving the nest for the first time or whenever the insects had difficulties finding the nest during their previous return. Ground-nesting bees and wasps perform such learning flights daily when they depart for the first time. During these flights, the insects turn back to face the nest entrance and subsequently back away from the nest while flying along ever increasing arcs that are centred on the nest. Flying along these arcs, the insects counter-turn in such a way that the nest entrance is always seen in the frontal visual field at slightly lateral positions. Here we asked how the insects may achieve keeping track of the nest entrance location given that it is a small, inconspicuous hole in the ground, surrounded by complex natural structures that undergo unpredictable perspective transformations as the insect pivots around the area and gains distance from it. We reconstructed the natural visual scene experienced by wasps and bees during their learning flights and applied a number of template-based tracking methods to these image sequences. We find that tracking with a fixed template fails very quickly in the course of a learning flight, but that continuously updating the template allowed us to reliably estimate nest direction in reconstructed image sequences. This is true even for later sections of learning flights when the insects are so far away from the nest that they cannot resolve the nest entrance as a visual feature. We discuss why visual goal-anchoring is likely to be important during the acquisition of visual-spatial memories and describe experiments to test whether insects indeed update nest-related templates during their learning flights. © 2014 Springer International Publishing Switzerland.Item Open Access A hybrid method for 6-DOF tracking of MRI-compatible robotic interventional devices(2006-05) Krieger, A.; Metzger, G.; Fichtinger, G.; Atalar, Ergin; Whitcomb L. L.This paper reports a novel hybrid method of tracking the position and orientation of robotic medical instruments within the imaging volume of a magnetic resonance imaging (MRI) system. The method utilizes two complementary measurement techniques: passive MRI fiducial markers and MRI-compatible joint encoding. This paper reports an experimental evaluation of the tracking accuracy of this system. The accuracy of this system compares favorably to that of a previously reported active tracking system. Moreover, the hybrid system is quickly and easily deployed on different MRI scanner systems. © 2006 IEEE.Item Open Access Mean-shift tracking of moving objects using multi-dimensional histograms(Society of Photo-Optical Instrumentation Engineers (SPIE), 2004-04) Cüce, Halil I.; Çetin, A. EnisIn this paper, a moving object tracking algorithm for infrared image sequences is presented. The tracking algorithm is based on the mean-shift tracking method which is based on comparing the histograms of moving objects in consecutive image frames. In video obtained after visible light, the color histogram of the object is used for tracking. In forward looking infrared image sequences, the histogram is constructed not only from the pixel values but also from a highpass filtered version of the original image. The reason behind the use of highpass filter outputs in histogram construction is to capture structural nature of the moving object. Simulation examples are presented.Item Open Access Mechanical design and position control of a modular mechatronic device (MechaCell)(IEEE, 2015) Ristevski, Stefan; Çakmakçı, MelihManufacturing techniques have advanced exponentially in recent years, providing means for production of smaller and more powerful electronics, which makes it compelling to design small and more powerful robots. Our work focuses on a mechanical design and position control of a modular mechatronic device called MechaCell. Mechacells are designed as modular semi-autonomous devices which can be used alone or part of a pack. In this paper our main focus is on the mechanical design of the Mechacell, especially the locomotion system which uses forces produced by a rotating unbalance that moves in a spherical domain for steering of the Mechacell. As part of the supervisory algorithm an overhead HD camera is used for position tracking of the Mechacell; the data is then sent to the Mechacells through a wireless connection. A proportional integral derivative controller is used as a base controller; then a friction compensation algorithm is added, based on the mathematical model of the Mechacell's locomotion system. Steering and locomotion controller of the Mechacell is validated using a complex motion profile in the developed testbed.Item Open Access Moving object detection in video by detecting non-Gaussian regions in subbands and active contours(IEEE, 2003-09) Gök, M. Y.; Çetin, A. EnisA multi-stage moving object detection algorithm in video is described in this paper. First, the camera motion is eliminated by motion compensation. An adaptive subband decomposition structure is then used to analyze the difference image. In the high-band subimages, moving objects which produce outliers are detected using a statistical test determining non-Gaussian regions. It turns out that the distribution of the subimage pixels is almost Gaussian in general. But, at the object boundaries the distribution of the pixels in the subimages deviates from Gaussianity due to the existence of outliers. Regions containing moving objects in the original image frame are detected by detecting regions containing outliers in subimages. Finally, active contours are initiated in these regions in the wavelet domain and object boundaries are accurately estimated.Item Open Access Object tracking under illumination variations using 2D-cepstrum characteristics of the target(IEEE, 2010) Cogun, Fuat; Çetin, A. EnisMost video processing applications require object tracking as it is the base operation for real-time implementations such as surveillance, monitoring and video compression. Therefore, accurate tracking of an object under varying scene conditions is crucial for robustness. It is well known that illumination variations on the observed scene and target are an obstacle against robust object tracking causing the tracker lose the target. In this paper, a 2D-cepstrum based approach is proposed to overcome this problem. Cepstral domain features extracted from the target region are introduced into the covariance tracking algorithm and it is experimentally observed that 2D-cepstrum analysis of the target object provides robustness to varying illumination conditions. Another contribution of the paper is the development of the co-difference matrix based object tracking instead of the recently introduced covariance matrix based method. ©2010 IEEE.Item Open Access Ordinal covering using block designs(IEEE, 2010) Atmaca, Abdullah; Oruc, A.Y.A frequently encountered problem in peer review systems is to facilitate pairwise comparisons of a given set of documents by as few experts as possible. In [7], it was shown that, if each expert is assigned to review k documents then ⌈n(n-1)/k(k-1)⌉ experts are necessary and ⌈n(2n-k)/k 2⌉ experts are sufficient to cover all n(n-1)/2 pairs of n documents. In this paper, we show that, if √n ≤ k ≤ n/2 then the upper bound can be improved using a new assignnment method based on a particular family of balanced incomplete block designs. Specifically, the new method uses ⌈n(n+k)/k2⌉ experts where n/k is a prime power, n divides k2, and √n ≤ k ≤ n/2. When k = √n , this new method uses the minimum number of experts possible and for all other values of k, where √n < k ≤ n/2, the new upper bound is tighter than the general upper bound given in [7]. ©2010 IEEE.Item Open Access Ordinal evaluation and assignment problems(IEEE, 2010) Atmaca, Abdullah; Oruç, A. YavuzIn many assignment problems, a set of documents such as research proposals, promotion dossiers, resumes of job applicants is assigned to a set of experts for ordinal evaluation, ranking, and classification. A desirable condition for such assignments is that every pair of documents is compared and ordered by one or more experts. This condition was modeled as an optimization problem and the number of pairs of documents was maximized for a given incidence relation between a set of documents and a set of experts using a set covering integer programming method in the literature[5]. In this paper, we use a combinatorial approach to derive lower bounds on the number of experts needed to compare all pairs of documents and describe assignments that asymptotically match these bounds. These results are not only theoretically interesting but also have practical implications in obtaining optimal assignments without using complex optimization techniques. ©2010 IEEE.Item Open Access Range estimation using simple infrared sensors without prior knowledge of surface parameters(IEEE, 2004) Yüzbaşıoğlu, Çağrı; Barshan, BillurThis paper describes a new method for range estimation using low-cost infrared sensors. The intensity data obtained with infrared sensors depends highly on the surface properties and the configuration of the sensors and the surface. Therefore, in many of the related studies, either the properties of the surface are determined first or certain assumptions about the surface are made in order to calculate the distance and the orientation of the surface relative to the sensors. In this paper, we propose a novel method for position estimation of surfaces with infrared sensors without the need to determine the surface properties first. The method is verified experimentally with planar surfaces covered with white paper, wooden block, bubbled packing material, white styrofoam, blue and brown cardboard. The overall absolute mean error in the range estimates has been calculated as 0.21 cm in the range from 12.5 to 45 cm. The results obtained demonstrate that infrared sensors can be easily used for localization to an unexpectedly high accuracy without prior knowledge of the surface parameters.Item Open Access Regional model-based computerized ionospheric tomography using GPS measurements: IONOLAB-CIT(Wiley-Blackwell Publishing, Inc., 2015) Tuna, H.; Arıkan, Orhan; Arikan, F.Three-dimensional imaging of the electron density distribution in the ionosphere is a crucial task for investigating the ionospheric effects. Dual-frequency Global Positioning System (GPS) satellite signals can be used to estimate the slant total electron content (STEC) along the propagation path between a GPS satellite and ground-based receiver station. However, the estimated GPS-STEC is very sparse and highly nonuniformly distributed for obtaining reliable 3-D electron density distributions derived from the measurements alone. Standard tomographic reconstruction techniques are not accurate or reliable enough to represent the full complexity of variable ionosphere. On the other hand, model-based electron density distributions are produced according to the general trends of ionosphere, and these distributions do not agree with measurements, especially for geomagnetically active hours. In this study, a regional 3-D electron density distribution reconstruction method, namely, IONOLAB-CIT, is proposed to assimilate GPS-STEC into physical ionospheric models. The proposed method is based on an iterative optimization framework that tracks the deviations from the ionospheric model in terms of F2 layer critical frequency and maximum ionization height resulting from the comparison of International Reference Ionosphere extended to Plasmasphere (IRI-Plas) model-generated STEC and GPS-STEC. The suggested tomography algorithm is applied successfully for the reconstruction of electron density profiles over Turkey, during quiet and disturbed hours of ionosphere using Turkish National Permanent GPS Network.Item Open Access Sentioscope: a soccer player tracking system using model field particles(Institute of Electrical and Electronics Engineers, 2016) Baysal, S.; Duygulu, P.Tracking multiple players is crucial to analyze soccer videos in real time. Yet, rapid illumination changes and occlusions among players who look similar from a distance make tracking in soccer very difficult. Particle-filter-based approaches have been utilized for their ability in tracking under occlusion and rapid motions. Unlike the common practice of choosing particles on targets, we introduce the notion of shared particles densely sampled at fixed positions on the model field. We globally evaluate targets' likelihood of being on the model field particles using our combined appearance and motion model. This allows us to encapsulate the interactions among the targets in the state-space model and track players through challenging occlusions. The proposed tracking algorithm is embedded into a real-life soccer player tracking system called Sentioscope. We describe the complete steps of the system and evaluate our approach on large-scale video data gathered from professional soccer league matches. The experimental results show that the proposed algorithm is more successful, compared with the previous methods, in multiple-object tracking with similar appearances and unpredictable motion patterns such as in team sports. © 1991-2012 IEEE.Item Open Access Vision-based continuous Graffiti™-like text entry system(SPIE, 2004) Erdem, İ. A.; Erdem, M. E.; Atalay, V.; Çetin, A. EnisIt is now possible to design real-time, low-cost computer version systems even in personal computers due to the recent advances in electronics and the computer industry. Due to this reason, it is feasible to develop computer-vision-based human-computer interaction systems. A vision-based continuous Graffiti™-like text entry system is presented. The user sketches characters in a Griffiti™-like alphabet in a continuous manner on a flat surface using a laser pointer. The beam of the laser pointer is tracked on the image sequences captured by a camera, and the corresponding written word is recognized from the extracted trace of the laser beam. © 2004 Society of Photo-Optical Instrumentation Engineers.