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In order to improve the quality of steel pipes, one of the main requisites is to build pipes that are as close as possible to the designed one. To accomplish this task, an optical distance sensor of reduced size and very low power consumption was developed inside a measurement system allowing reconstruction of steel pipe dimensions. The results obtained led to the construction of a working prototype configured as an active triangulation rangefinder with a gamut of 10 cm starting at 5 cm. The characterization of the novel rangefinder has confirmed the feasibility of this new system with a resolution of \sim 10~\mu \textm on a range of measurement of 10 cm, providing up to 10 000 measurements per second. [ABSTRACT FROM PUBLISHER]

Object triangulation, 3-D object tracking, feature correspondence, and camera calibration are key problems for estimation from camera networks. This paper addresses these problems within a unified Bayesian framework for joint multi-object tracking and camera calibration, based on the finite set statistics methodology. In contrast to the mainstream approaches, an alternative parametrization is investigated for triangulation, called disparity space. The approach for feature correspondence is based on the probability hypothesis density (phd) filter, and hence inherits the ability to handle the initialization of new tracks as well as the discrimination between targets and clutter within a Bayesian paradigm. The phd filtering approach then forms the basis of a camera calibration method from static or moving objects. Results are shown on simulated and real data. [ABSTRACT FROM AUTHOR]

Solder ball height and substrate coplanarity inspection is essential to the detection of potential connectivity issues in semi-conductor units. Current ball height and substrate coplanarity inspection tools such as laser profiling, fringe projection, and confocal microscopy are expensive, require complicated setup and are slow, which makes them difficult to use in a real-time manufacturing setting. Therefore, a reliable, in-line ball height and substrate coplanarity measurement method is needed for inspecting units undergoing assembly. [ABSTRACT FROM AUTHOR]

This paper proposes a method for designing base station (BS) clusters and cluster patterns for pair-wise BS coordination. The key idea is that each BS cluster is formed by using the second-order Voronoi region, and the BS clusters are assigned to a specific cluster pattern by using edge-coloring for a graph drawn by Delaunay triangulation. The main advantage of the proposed method is that the BS selection conflict problem is prevented, while users are guaranteed to communicate with their two closest BSs in any irregular BS topology. With the proposed coordination method, analytical expressions for the rate distribution and the ergodic spectral efficiency are derived as a function of relevant system parameters in a fixed irregular network model. In a random network model with a homogeneous Poisson point process, a lower bound on the ergodic spectral efficiency is characterized. Through system level simulations, the performance of the proposed method is compared with that of conventional coordination methods: dynamic clustering and static clustering. Our major finding is that, when users are dense enough in a network, the proposed method provides the same level of coordination benefit with dynamic clustering to edge users. [ABSTRACT FROM AUTHOR]

This research focuses on distributed and localized algorithms for precise boundary detection in 3-D wireless networks. Our objectives are twofold. First, we aim to identify the nodes on the boundaries of a 3-D network, which serve as a key attribute that characterizes the network, especially in such geographic exploration tasks as terrain and underwater reconnaissance. Second, we construct locally planarized 2-manifold surfaces for inner and outer boundaries in order to enable available graph theory tools to be applied on 3-D surfaces, such as embedding, localization, partition, and greedy routing among many others. To achieve the first objective, we propose a Unit Ball Fitting (UBF) algorithm that discovers a majority of boundary nodes, followed by a refinement algorithm, named Isolated Fragment Filtering (IFF), to remove isolated nodes that are misinterpreted as boundary nodes. Based on the identified boundary nodes, we develop an algorithm that constructs a locally planarized triangular mesh surface for each 3-D boundary. Our proposed scheme is localized, requiring information within 1-hop neighborhood only. We further extend the schemes for online boundary detection in mobile sensor networks aiming to achieve low overhead. Our simulation and experimental results demonstrate that the proposed algorithms can effectively identify boundary nodes and surfaces, even under high measurement errors. [ABSTRACT FROM PUBLISHER]

We developed a new method for extracting 3D flight trajectories of droplets using high-speed stereo capture. We noticed that traditional multi-camera tracking techniques fare poorly on our problem, in part due to the fact that all droplets have very similar shapes, sizes and appearances. Our method uses local motion models to track individual droplets in each frame. 2D tracks are used to learn a global, non-linear motion model, which in turn can be used to estimate the 3D locations of individual droplets even when these are not visible in any camera. We have evaluated the proposed method on both synthetic and real data and our method is able to reconstruct 3D flight trajectories of hundreds of droplets. The proposed technique solves for both the 3D trajectory of a droplet and its motion model concomitantly, and we have found it to be superior to 3D reconstruction via triangulation. Furthermore, the learned global motion model allows us to relax the simultaneity assumptions of stereo camera systems. Our results suggest that, even when full stereo information is available, our unsynchronized reconstruction using the global motion model can significantly improve the 3D estimation accuracy. [ABSTRACT FROM PUBLISHER]

Positioning is a fundamental issue in mobile robot applications, and it can be achieved in multiple ways. Among these methods, triangulation based on angle measurements is widely used, robust, accurate, and flexible. This paper presents BeAMS, which is a new active beacon-based angle measurement system used for mobile robot positioning. BeAMS introduces several major innovations. One innovation is the use of a unique unsynchronized channel with on–off keying modulated infrared signals to measure angles and to identify the beacons. We also introduce a new mechanism to measure angles: Our system detects a beacon when it enters and leaves an angular window. We show that the estimator resulting from the center of this angular window provides an unbiased estimate of the beacon angle. A theoretical framework for a thorough performance analysis of BeAMS is provided. We establish the upper bound of the variance and validate this bound through experiments and simulations; the overall error measure of BeAMS is lower than \0.24^\circ for an acquisition rate of 10\,\Hz. In conclusion, BeAMS is a low-power, flexible, and robust solution for angle measurement and a reliable component for robot positioning. [ABSTRACT FROM PUBLISHER]

Positioning is a fundamental issue in mobile robot applications. It can be achieved in many ways. Among them, triangulation based on angles measured with the help of beacons is a proven technique. Most of the many triangulation algorithms proposed so far have major limitations. For example, some of them need a particular beacon ordering, have blind spots, or only work within the triangle defined by the three beacons. More reliable methods exist; however, they have an increasing complexity, or they require to handle certain spatial arrangements separately. In this paper, we present a simple and new three object triangulation algorithm, known as ToTal, that natively works in the whole plane and for any beacon ordering. We also provide a comprehensive comparison between many algorithms and show that our algorithm is faster and simpler than comparable algorithms. In addition to its inherent efficiency, our algorithm provides a very useful and unique reliability measure that is assessable anywhere in the plane, which can be used to identify pathological cases, or as a validation gate in Kalman filters. [ABSTRACT FROM PUBLISHER]

Node self-localization is a key research topic for wireless sensor networks (WSNs). There are two main algorithms, the triangulation method and the maximum likelihood (ML) estimator, for angle of arrival (AOA) based self-localization. The ML estimator requires a good initialization close to the true location to avoid divergence, while the triangulation method cannot obtain the closed-form solution with high efficiency. In this paper, we develop a set of efficient closed-form AOA based self-localization algorithms using auxiliary variables based methods. First, we formulate the self-localization problem as a linear least squares problem using auxiliary variables. Based on its closed-form solution, a new auxiliary variables based pseudo-linear estimator (AVPLE) is developed. By analyzing its estimation error, we present a bias compensated AVPLE (BCAVPLE) to reduce the estimation error. Then we develop a novel BCAVPLE based weighted instrumental variable (BCAVPLE-WIV) estimator to achieve asymptotically unbiased estimation of locations and orientations of unknown nodes based on prior knowledge of the AOA noise variance. In the case that the AOA noise variance is unknown, a new AVPLE based WIV (AVPLE-WIV) estimator is developed to localize the unknown nodes. Also, we develop an autonomous coordinate rotation (ACR) method to overcome the tangent instability of the proposed algorithms when the orientation of the unknown node is near \pi/2. We also derive the Cramér-Rao lower bound (CRLB) of the ML estimator. Extensive simulations demonstrate that the new algorithms achieve much higher localization accuracy than the triangulation method and avoid local minima and divergence in iterative ML estimators. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel interactive projection system (IPS), which enables bare-finger touch interaction on regular planar surfaces (e.g., walls, tables), with only one standard camera and one projector. The challenge of bare-finger touch detection is recovering the touching information just from the 2-D image captured by the camera. In our method, the graphical user interface (GUI) button is projected on the surface and is distorted by the finger when clicking it, and there is a significant positive correlation between the button's distortion and the finger's height to the surface. Therefore, we propose a novel, fast, and robust algorithm, which takes advantage of the button's distortion to detect the touch action. The proposed touch detection algorithm is performed in three stages: 1) region of interest extraction through a homography mapping, by which the computational complexity of the following processing is reduced; 2) the button's distortion detection using a special edge detection algorithm, which greatly reduces the errors due to the influence of the finger's shadows and edges; and 3) touch action judgment by the button's distortion. Several applications (e.g., virtual keyboard, power point viewing), which use the proposed touch detection method based on the buttons, are shown in this paper. An evaluation is performed on the virtual keyboard and the results demonstrate that the proposed approach can detect bare-finger touch in real time with the missed detection rate of 1.00%, false detection rate of 2.08%, and touch detection rate of 96.92% at the typical projected distance. [ABSTRACT FROM AUTHOR]

In this paper, a deterministic sensor deployment method based on wavelet transform (WT) is proposed. It aims to maximize the quality of coverage of a wireless sensor network while deploying a minimum number of sensors on a 3-D surface. For this purpose, a probabilistic sensing model and Bresenham's line of sight algorithm are utilized. The WT is realized by an adaptive thresholding approach for the generation of the initial population. Another novel aspect of the paper is that the method followed utilizes a Cat Swarm Optimization (CSO) algorithm, which mimics the behavior of cats. We have modified the CSO algorithm so that it can be used for sensor deployment problems on 3-D terrains. The performance of the proposed algorithm is compared with the Delaunay Triangulation and Genetic Algorithm based methods. The results reveal that CSO based sensor deployment which utilizes the wavelet transform method is a powerful and successful method for sensor deployment on 3-D terrains. [ABSTRACT FROM PUBLISHER]

We propose the first graphics processing unit (GPU) solution to compute the 2D constrained Delaunay triangulation (CDT) of a planar straight line graph (PSLG) consisting of points and edges. There are many existing CPU algorithms to solve the CDT problem in computational geometry, yet there has been no prior approach to solve this problem efficiently using the parallel computing power of the GPU. For the special case of the CDT problem where the PSLG consists of just points, which is simply the normal Delaunay triangulation (DT) problem, a hybrid approach using the GPU together with the CPU to partially speed up the computation has already been presented in the literature. Our work, on the other hand, accelerates the entire computation on the GPU. Our implementation using the CUDA programming model on NVIDIA GPUs is numerically robust, and runs up to an order of magnitude faster than the best sequential implementations on the CPU. This result is reflected in our experiment with both randomly generated PSLGs and real-world GIS data having millions of points and edges. [ABSTRACT FROM PUBLISHER]

A sub-wavelength source tracking system utilizing highly miniaturized antennas in the HF range for applications in GPS-denied environments including indoor and urban scenarios is proposed. A technique that combines a high resolution direction finding and radio triangulation utilizing a compact transmit (Tx) and receive (Rx) antenna system is pursued. Numerical models are used to investigate wave propagation and scattering in complex indoor scenarios as a function of frequency. We choose HF band to minimize attenuation through walls and multipath in indoor environments. In order to achieve a compact system, a low-profile and highly miniaturized antenna (\lambda /300 height and \lambda /100 lateral dimensions at 20 MHz) having omnidirectional, vertically polarized field is designed. At such low frequencies, accurate measurement of the phase difference between the signals at the Rx antennas having very small baseline is challenging. To address this issue, a biomimetic circuit that mimics the hearing mechanism of a fly (Ormia Ochracea) is utilized. With this circuit, very small phase differences are amplified to measurable values. The numerical simulations are used to analyze direction of arrival retrieval and source localization in highly cluttered environments. A compact system prototype is also realized and source tracking in complex indoor scenarios is successfully demonstrated. [ABSTRACT FROM AUTHOR]

Almost all geographic routing protocols have been designed for 2-D. We present a novel geographic routing protocol, named Multihop Delaunay Triangulation (MDT), for 2-D, 3-D, and higher dimensions with these properties: 1) guaranteed delivery for any connected graph of nodes and physical links, and 2) low routing stretch from efficient forwarding of packets out of local minima. The guaranteed delivery property holds for node locations specified by accurate, inaccurate, or arbitrary coordinates. The MDT protocol suite includes a packet forwarding protocol together with protocols for nodes to construct and maintain a distributed MDT for routing. We present the performance of MDT protocols in 3-D and 4-D as well as performance comparisons of MDT routing versus representative geographic routing protocols for nodes in 2-D and 3-D. Experimental results show that MDT provides the lowest routing stretch in the comparisons. Furthermore, MDT protocols are specially designed to handle churn, i.e., dynamic topology changes due to addition and deletion of nodes and links. Experimental results show that MDT's routing success rate is close to 100% during churn, and node states converge quickly to a correct MDT after churn. [ABSTRACT FROM PUBLISHER]

This paper addresses the problem of computing the geodesic distance map from a given set of source vertices to all other vertices on a surface mesh using an anisotropic distance metric. Formulating this problem as an equivalent control theoretic problem with Hamilton-Jacobi-Bellman partial differential equations, we present a framework for computing an anisotropic geodesic map using a curvature-based speed function. An ordered upwind method (OUM)-based solver for these equations is available for unstructured planar meshes. We adopt this OUM-based solver for surface meshes and present a triangulation-invariant method for the solver. Our basic idea is to explore proximity among the vertices on a surface while locally following the characteristic direction at each vertex. We also propose two speed functions based on classical curvature tensors and show that the resulting anisotropic geodesic maps reflect surface geometry well through several experiments, including isocontour generation, offset curve computation, medial axis extraction, and ridge/valley curve extraction. Our approach facilitates surface analysis and processing by defining speed functions in an application-dependent manner. [ABSTRACT FROM AUTHOR]

The localization method of a magnetic dipole based on the magnetic gradient tensor invariants is the Scalar Triangulation And Ranging method (STAR), which is used to solve the multiple solutions problem for the real-time localization of magnetic dipole by the spatial geometric relationship of the tensor rotation invariants. The method is not involved in the measurement of the magnetic field vector greatly affected by the geomagnetic field. Simultaneously, it is very suitable for underground and underwater exploration such as the exploration of unexploded ordnance. But, it has asphericity errors, which can make the azimuth errors of up to 5^\circ. In addition, it is tightly coupled with the magnetic properties of the target. Thus, we proposed an iterative method to correct the asphericity errors. In this method, beginning with the results of the STAR method, the defective parameters obtained by the sensor structure were used to rapidly correct the localization errors and enhance the properties of real-time localization. The relative errors of the components of bearing vector were reduced by a factor of 7, and they were not influenced by the magnetic properties of the target. [ABSTRACT FROM AUTHOR]

A new exact algorithm is proposed to compute the 3D geometric moments of a homogeneous shape defined by an unstructured triangulation of its surface. This algorithm relies on the analytical integration of the moments on tetrahedra defined by the surface triangles and a central point and on a set of recurrent relationships between the corresponding integrals, and achieves linear running time complexities with respect to the number of triangles in the surface mesh and with respect to the number of moments that are computed. This effectively reduces the complexity for computing moments up to order N from N^6 to N^3 with respect to the fastest previously proposed exact algorithm. [ABSTRACT FROM AUTHOR]

Quality evaluation of rolling processes in the metal industry involves an inspection of the shape of the outgoing products in real time during manufacturing. Shape measurement systems are usually based on 3-D reconstructions of the surface of rolled products. As surface properties are crucial, these systems favor contactless techniques. Using 3-D measurements of the surface of rolled products, several geometric properties can be analyzed. In this paper, we analyze how uncertainty is propagated in a contactless shape measurement system designed and developed by the authors and presented in previous published works. This measurement system is based on active triangulation, and it is able to provide inline width and flatness measurements of long, flat-rolled products in harsh industrial environments. The camera model used to calibrate the vision system is described, and it is used to estimate the uncertainty of the reprojected 3-D points on the scene. The system uses the reprojected 3-D points, and the speed of the product movement in the production line to reconstruct its surface. Thus, the uncertainty of the speed is also estimated. Finally, the propagation of both the uncertainty of the 3-D reprojection, and the uncertainty of the speed into the final width and flatness measurements is analyzed. This paper comprises a detailed uncertainty propagation analysis in 3-D shape measurements computed indirectly through functional relationships. [ABSTRACT FROM AUTHOR]

Escape routing for packages and printed circuit boards (PCBs) has been studied extensively in the past. Network flow is pervasively used to model this problem. However, none of the previous works correctly models the diagonal capacity, which is essential for 45 \circ routing in most packages and PCBs. As a result, existing algorithms may either produce routing solutions that violate the diagonal capacity or fail to output a legal routing even though there exists one. In this paper, we propose a new network flow model that guarantees the correctness when diagonal capacity is taken into consideration. This model leads to the first optimal algorithm for escape routing. We also extend our model to handle missing pins. 45 [ABSTRACT FROM AUTHOR]

We present a simple approach to jointly exploit stripmap and ScanSAR acquisitions to generate differential synthetic aperture radar interferometry (DInSAR) time series. In particular, we extend the capability of the Small BAseline Subset (SBAS) approach to compute deformation time series from a set of stripmap images by filling possible temporal gaps in the available SAR data sequence with ScanSAR acquisitions. The starting point of our approach is the raw data focusing step, which is properly carried out to align the characteristics of the ScanSAR images to those of the stripmap ones. To achieve this task, we exploit stripmap processing codes to focus both SAR data types, the ScanSAR ones being processed on a burst-by-burst basis, accounting also for possible differences of the pulse repetition frequency with respect to that of the stripmap data. The coherent combination of the focused bursts generates phase-preserved ScanSAR images with the same output geometry and pixel spacing as the stripmap ones. This allows a straightforward implementation of the next steps of the SBAS processing chain, including the interferogram generation operation. In this case, we concentrate on a selection of small baseline (SB) stripmap-stripmap multilook interferograms identified through a Delaunay triangulation, which are complemented with a set of hybrid SB stripmap-ScanSAR interferograms. This interferogram selection permits us to develop an effective phase unwrapping algorithm based on a two-step processing strategy. Finally, the whole data set of unwrapped interferograms is inverted through the SBAS technique to retrieve the final deformation time series, including both stripmap and ScanSAR data. The proposed stripmap-ScanSAR SBAS process ing approach is particularly attractive because it is very easy to implement since it requires only limited modifications with respect to the conventional stripmap-based SBAS algorithm. Our approach has been applied to descending and ascending hybrid stripmap-ScanSAR data sets of Envisat/ASAR C-band acquisitions from the Big Island of Hawaii. In spite of not including any common-band azimuthal filtering, which would account for the ScanSAR burst spectral properties at the expense of the algorithm simplicity, the presented results show that we may retrieve DInSAR time series with an accuracy ranging between 5 and 10 mm, consistent with previous C-band data analyses using only stripmap data. [ABSTRACT FROM PUBLISHER]

The miniaturization of an autonomous robot requires the integration of components that not only need to satisfy strict spatial constraints, but also need to demonstrate useful functionalities and performance, while demanding low power. For miniaturized autonomous robots that aim at exploring unknown environments, sensors for navigation and for the understanding of basic geometrical features of the environment are of utmost importance for a robot’s survival and mission. This paper presents a miniaturized triangulation laser scanner that was developed and characterized for use on a 10 \times 10 \times 10 cm^3 robot. The optimal configurations of the laser sensor on two sides of the robot are discussed, and measurement formulas as well as theoretical resolution are deduced. For indoor applications, the measurement range of the system runs from approximately 80 mm, with1 mm resolution, up to 600 mm, with 12 mm resolution. The aim of the work is to demonstrate the possibility of extracting basic information from the robot surroundings by means of small, simple, low-power, and low-cost demanding devices, which, in addition, can be scaled down in order to equip even smaller robots. [ABSTRACT FROM PUBLISHER]

As 3-D displays become more common, the demand for 3-D-related products is rapidly increased. Three-dimensional image sensors based on the time-of-flight (TOF) technique are one of these products and are applied to many applications. In this paper, a new pixel based on the continuous-wave modulation method was proposed to measure the TOF and was embedded in a test complementary metal–oxide–semiconductor (CMOS) image sensor. Compared with other range imagers, no complex control signals, high operating voltage, or multilevel control voltages are needed in this pixel. The chip, with 92 \times 30 pixels, was fabricated using the Taiwan Semiconductor Manufacturing Company's 0.18-\mu\m CMOS standard process, and a time-switched color measurement was applied to this rangefinder system. A pulse train of red, green, and blue lights is emitted sequentially from a light-emitting diode array. The distance is easily calculated from the phase differences, and the color information is estimated using the difference in reflection coefficients under a different light. The measured distance and color are compared with the actual distance and color-corrected images. A color range image with a distance error of 3.56 cm and an L^\ast a^\ast b color difference of 40.23 can be observed. This rangefinder system provides a new perspective to capturing a colored range image. [ABSTRACT FROM PUBLISHER]

To carry out face transformation, this paper presents new numerical algorithms, which consist of two parts, namely, the harmonic models for changes of face characteristics and the splitting techniques for grayness transition. The main method in this paper is a combination of the finite-volume method (FVM) with Delaunay triangulation to solve the Laplace equations in the harmonic transformation of face images. The advantages of the FVM with Delaunay triangulation are given as follows: 1) easy to formulate the linear algebraic equations; 2) good in retaining the pertinent geometric and physical need; and 3) less central processing unit time needed. Numerical and graphical experiments have been conducted for the face transformation from a female (woman) to a male (man), and vice versa. The computed sequential errors are O(N^-(3/2)), where N^2 is the division number of a pixel into subpixels. These computed errors coincide with the analysis on the splitting–shooting method (SSM) with piecewise constant interpolation in the previous paper of Li and Bai. In computation, the average absolute errors of restored pixel grayness can be smaller than 2 out of 256 grayness levels. The FVM is as simple as the finite-difference method (FDM) and as flexible as the finite-element method (FEM). Hence, the FVM is particularly useful when dealing with large face images with a huge number of pixels in shape distortion. The numerical transformation of face images in this paper can be used not only in pattern recognition but also in resampling, image morphing, and computer animation. [ABSTRACT FROM AUTHOR]

Given the hyperspectral-oriented waveband configuration of multiangular CHRIS/Proba imagery, the scope of its application could widen if the present 18-m resolution would be improved. The multiangular images of CHRIS could be used as input for superresolution (SR) image reconstruction. A critical procedure in SR is an accurate registration of the low-resolution images. Conventional methods based on affine transformation may not be effective given the local geometric distortion in high off-nadir angular images. This paper examines the use of a nonrigid transform to improve the result of a nonuniform interpolation and deconvolution SR method. A scale-invariant feature transform is used to collect control points (CPs). To ensure the quality of CPs, a rigorous screening procedure is designed: 1) an ambiguity test; 2) the m-estimator sample consensus method; and 3) an iterative method using statistical characteristics of the distribution of random errors. A thin-plate spline (TPS) nonrigid transform is then used for the registration. The proposed registration method is examined with a Delaunay triangulation-based nonuniform interpolation and reconstruction SR method. Our results show that the TPS nonrigid transform allows accurate registration of angular images. SR results obtained from simulated LR images are evaluated using three quantitative measures, namely, relative mean-square error, structural similarity, and edge stability. Compared to the SR methods that use an affine transform, our proposed method performs better with all three evaluation measures. With a higher level of spatial detail, SR-enhanced CHRIS images might be more effective than the original data in various applications. [ABSTRACT FROM AUTHOR]

In this correspondence, preamble-based least squares (LS) channel estimation in orthogonal frequency division multiplexing (OFDM) systems of the QAM and offset QAM (OQAM) types is considered. The construction of optimal (in the mean squared error (MSE) sense) preambles is investigated, for sparse (a subset of pilot tones, surrounded by nulls) preambles. The two OFDM systems are compared for the same transmit power, which, for cyclic prefix (CP) based OFDM/QAM, also includes the power spent for CP transmission. OFDM/OQAM, with a sparse preamble consisting of equipowered and equispaced pilots embedded in zeros, turns out to perform at least as well as CP-OFDM. Simulations results are presented that verify the analysis. [ABSTRACT FROM AUTHOR]

A new technique to compute the physical optics (PO) integral is presented. The technique consists of a blind code that computes the different contributions (stationary phase points, end points, etc.) numerically. This technique is based on a decomposition of the surface into small triangles and a fast evaluation of each triangle by means of a deformation of the integration path in the complex plane. This algorithm permits a fast and accurate evaluation of the PO integral for smooth large surfaces. The CPU time is almost independent of frequency. [ABSTRACT FROM AUTHOR]

In this paper, we propose a segment-based triangulation method for building parallel-perspective stereo mosaics using ray interpolation. The currently available fast parallel ray interpolation for stereo mosaicing uses a uniform or regular triangulation technique that does not take advantage of the spatial information. This works well when the interframe displacement in the video is small. However, for large interframe displacements, hence large motion parallax, we observe visual artifacts in the mosaics when the source triangles in the video frames are warped into destination triangles in the mosaics using affine transformations. Our method uses the edge information present in the scene to ensure that triangles do not cross over from one planar facet to the other. The video frames are segmented, and the edges are obtained from the inner boundaries of different segments. A mesh is designed in each segment or region, over which motion between consecutive video frames is constant. Hence, this method avoids unwanted warping of objects with large motion parallax in the scene and reduces the visual artifacts. The performance of our proposed technique is demonstrated on a series of simple-to-complex video imagery collected by utilizing cameras and airborne sensors. [ABSTRACT FROM AUTHOR]

We present an algorithm for distributed sensor localization with noisy distance measurements (DILAND) that extends and makes the DLRE more robust. DLRE is a distributed sensor localization algorithm in ℝm (m ⩾1) introduced in our previouswork (IEEE Trans. Signal Process., vol. 57, no. 5, pp. 2000-2016, May 2009). DILAND operates when: 1) the communication among the sensors is noisy; 2) the communication links in the network may fail with a nonzero probability; and 3) the measurements performed to compute distances among the sensors are corrupted with noise. The sensors (which do not know their locations) lie in the convex hull of at least m+1 anchors (nodes that know their own locations). Under minimal assumptions on the connectivity and triangulation of each sensor in the network, we show that, under the broad random phenomena described above, DILAND converges almost surely (a.s.) to the exact sensor locations. [ABSTRACT FROM AUTHOR]

Peer-to-peer (P2P) streaming has been widely deployed over the Internet. A streaming system usually has multiple channels, and peers may form multiple groups for content distribution. In this paper, we propose a distributed overlay framework (called SMesh) for dynamic groups where users may frequently hop from one group to another while the total pool of users remain stable. SMesh first builds a relatively stable mesh consisting of all hosts for control messaging. The mesh supports dynamic host joining and leaving, and will guide the construction of delivery trees. Using the Delaunay Triangulation (DT) protocol as an example, we show how to construct an efficient mesh with low maintenance cost. We further study various tree construction mechanisms based on the mesh, including embedded, bypass, and intermediate trees. Through simulations on Internet-like topologies, we show that SMesh achieves low delay and low link stress. [ABSTRACT FROM AUTHOR]

We present a fast algorithm to approximate the swept volume (SV) boundary of arbitrary polygon soup models. Despite the extensive research on calculating the volume swept by an object along a trajectory, the efficient algorithms described have imposed constraints on both the trajectories and geometric models. By proposing a general algorithm that handles flat surfaces as well as volumes and disconnected objects, we allow SV calculation without resorting to preprocessing mesh repair nor deforming offsets. This is of particular interest in the domain of product lifecycle management (PLM), which deals with industrial computer aided design (CAD) models that are malformed more often than not. We incorporate the bounded distance operator used in path planning to efficiently sample the trajectory while controlling the total error. We develop a triangulation scheme that draws on the unique data set created by an advancing front level-set method to tessellate the SV boundary in linear time. We analyze its performance, and demonstrate its effectiveness both theoretically and on real cases taken from PLM. Note to Practitioners-Swept volumes are useful for collision detection, ergonomics, mechanical assembly, and many other fields. We successfully tested our method on actual industrial models, including a digital actor. Therefore, no additional work is required in order to put our technique into practice for polygon soup models. Additionally, the graphics card is only used in a way that is easily accessible without special GPU programming. [ABSTRACT FROM AUTHOR]