When time difference of arrival (TDOA)-based bearing measurements are used in passive triangulation, the accuracy of localization depends on the geometric relationship between the emitter and the sensors. In particular, the localization accuracy varies with the geometric conditions in TDOA-based direction finding (DF) for bearing measurement and lines of bearing (LOBs) crossing for triangulation. To obtain an accurate estimate in passive triangulation using TDOA-based bearing measurements, we shall use these bearings selectively by considering geometric dilution of precision (GDOP) between the emitter and the sensors. To achieve this goal, we first define two GDOPs related to TDOA-based DF and LOBs crossing geometries, and then propose a new hybrid GDOP by combining these GDOPs for a better selection of bearings. Subsequently, two bearings with the lowest hybrid GDOP condition are chosen as the inputs to a triangulation localization algorithm. In simulations, the proposed method shows its enhancement to the localization accuracy.

Massive digital elevation models require a large number of geometric primitives that exceed the throughput of the existing graphics hardware. For the interactive visualization of these datasets, several adaptive reconstruction methods that reduce the number of primitives have been introduced over the decades. Quadtree triangulation, based on subdivision of the terrain into rectangular patches at different resolutions, is the most frequently used terrain reconstruction method. This usually accomplishes the triangulation using LOD (level-of-detail) selection and crack removal based on geometric errors. In this paper, we present bimodal vertex splitting, which performs LOD selection and crack removal concurrently on a GPU. The first mode splits each vertex for LOD selection and the second splits each vertex for crack removal. By performing these two operations concurrently on a GPU, we can efficiently accelerate the rendering speed by reducing the computation time and amount of transmission data in comparison with existing quadtree-based rendering methods.

In a rooted triangulated planar graph, an outer vertex and two outer edges incident to it are designated as its root, respectively. Two plane embeddings of rooted triangulated planar graphs are defined to be equivalent if they admit an isomorphism such that the designated roots correspond to each other. Given a positive integer n, we give an O(n)-space and O(1)-time delay algorithm that generates all biconnected rooted triangulated planar graphs with at most n vertices without delivering two reflectively symmetric copies.

With the increasing popularity of multicast and real-time streaming service applications, efficient channel assignment algorithms that handle both multicast and unicast traffic in wireless mesh networks are needed. One of the most effective approaches to enhance the capacity of wireless networks is to use systems with multiple channels and multiple radio interfaces. However, most of the past works focus on vertex coloring of a general contention graph, which is NP-Complete, and use the greedy algorithm to achieve a suboptimal result. In this paper, we combine unicast and multicast with a transmission set, and propose a framework named Chordal Graph Based Channel Assignment (CGCA) that performs channel assignment for multicast and unicast traffic in multi-channel multi-radio wireless mesh networks. The proposed framework based on chordal graph coloring minimizes the interference of the network and prevents unicast traffic from starvation. Simulation results show that our framework provides high throughput and low end-to-end delay for both multicast and unicast traffic. Furthermore, our framework significantly outperforms other well-known schemes that have a similar objective in various scenarios.

We present an alternative approach to what we call the "standard optimization", which minimizes a cost function by searching a parameter space. Instead, our approach "projects" in the joint observation space onto the manifold defined by the "consistency constraint", which demands that any minimal subset of observations produce the same result. This approach avoids many difficulties encountered in the standard optimization. As typical examples, we apply it to line fitting and multiview triangulation. The latter produces a new algorithm far more efficient than existing methods. We also discuss the optimality of our approach.

In recent years, digital maps have been used in a variety of scenarios, including car navigation systems and map information services over the Internet. These digital maps are formed by multiple layers of maps of different scales; the map data most suitable for the specific situation are used. Currently, the production of map data of different scales is done by hand due to constraints related to processing time and accuracy. We conducted research concerning technologies for automatic generation of simplified map data from detailed map data. In the present paper, the authors propose the following: (1) a method to transform data related to streets, rivers, etc. containing widths into line data, (2) a method to eliminate the component points of the data, and (3) a method to eliminate data that lie below a certain threshold. In addition, in order to evaluate the proposed method, a user survey was conducted; in this survey we compared maps generated using the proposed method with the commercially available maps. From the viewpoint of the amount of data reduction and processing time, and on the basis of the results of the survey, we confirmed the effectiveness of the automatic generation of simplified maps using the proposed methods.

A new mesh reconstruction technique, called dividing virtual belt algorithm (DVBA), is proposed for approximating the surface from a set of wire-frame contours. DVBA decomposes the branching region into a set of virtual belts and virtual canyons. A tiling technique based on the divide-and-conquer strategy is also introduced to approximate the surface from the virtual belt, and the virtual canyons are covered by a conventional polygon triangulation technique. The experimental result shows that our method works well even though there are many complicated branches in the object.

We consider the problem of triangulating an x-monotone polygon with a small number of different edge lengths using Steiner points. Given a parameter α, where 0<α<1, we shall present an algorithm for finding an almost uniform triangular mesh with 3π/8α2+o(1/α2) different edge lengths such that every edge length is between l and (2+α)l. Experiments demonstrate the effectiveness of this algorithm.

In this paper, we propose a new localization scheme for wireless sensor networks consisting of a huge number of sensor nodes equipped with simple wireless communication devices such as wireless LAN and Bluetooth. The proposed scheme is based on the Point-In-Triangle (PIT) test proposed by He et al. The scheme is actually implemented by using Bluetooth devices of Class 2 standard, and the performance of the scheme is evaluated in an actual environment. The result of experiments indicates that the proposed scheme could realize a localization with an error of less than 2 m.

In this paper, we propose a construction method of three-dimensional deformable models that represent tree-shaped human organs, such as bronchial tubes, based on results obtained by statistically analyzing the distributions of bifurcation points in the tree-shaped organs. The models are made to be used as standard templates of tree-shaped organs in medical image recognition, and are formed by control points that can be uniquely identified as structural elements of organs such as bifurcation tracheae in bronchial tubes. They can be transfigured based on the statistical validity of relationships between the control points. The optimal state of that transfiguration is determined within the framework of energy minimization. Experimental results from bronchial tubes are shown on actual CT images.

In reconstructing 3-D from images based on feature points, one usually defines a triangular mesh that has these feature points as vertices and displays the scene as a polyhedron. If the scene itself is a polyhedron, however, some of the displayed edges may be inconsistent with the true shape. This paper presents a new technique for automatically eliminating such inconsistencies by using a special template. We also present a technique for removing spurious occluding edges. All the procedures do not require any thresholds to be adjusted. Using real images, we demonstrate that our method has high capability to correct inconsistencies.

In the past decade, significant effort has been made toward increasing the accuracy and robustness of three-dimensional scanning methods. In this paper, we present a new prototype vision system named 3D Model Studio, which has been built to reconstruct a complete 3D model in as less as a few minutes. New schemes for a probe calibration and a 3D data merging (axis consolidation) are employed. We also propose a new semi-automatic contour registration method to generate accurate contour model from 3D data points, along with a contour triangulation based surface reconstruction. Experimental result shows that our system works well for reconstructing a complete 3D surface model of a human body.

A "rooted" plane triangulation is a plane triangulation with one designated vertex r and one designated edge incident to r on the outer face. In this paper we give a simple algorithm to generate all connected rooted plane triangulations with at most m edges. The algorithm uses O(m) space and generates such triangulations in O(1) time per triangulation without duplications. The algorithm does not output entire triangulations but the difference from the previous triangulation. By modifying the algorithm we can generate all connected (non-rooted) plane triangulations with at most m edges in O(m3) time per triangulation.

The reflection signal in the inverse synthetic aperture radar is measured in the polar coordinate defined by the object rotation angle and the frequency. The reconstruction of fixed scene images requires the coordinate transformation of the polar format data into the rectangular spatial frequency domain, which is then processed by the inverse Fourier transform. In this paper a fast and flexible method of coordinate transformation based on the nearest neighbor interpolation utilizing the Delauney triangulation is at first presented. Then, the induced errors in the transformed rectangular spatial frequency data and the resultant fixed scene images are investigated by simulation under the uniform plane wave transmit-receive mode over the swept frequency 120-160 GHz, and the results which demonstrate the validity of the current coordinate transformation are presented.

Appropriate meshes are crucial for accurate and efficient 3D process simulation. In this paper, we present a set of tools operating on surface and interface triangulations. These tools allow the improvement of the accuracy of interfaces, the reduction of the number of triangles, and the removal of obtuse not coplanarily compensated triangles. The first tool is used within integrated topography simulation environments based on different data structures, e.g. cell-based and segment-based. The latter two are particularly important for providing appropriate input to mesh generation for 3D process simulation.

Triangulations have been one of main research topics in computational geometry and have many applications in computer graphics, finite element methods, mesh generation, etc. This paper surveys properties of triangulations in the two- or higher-dimensional spaces. For triangulations of the planar point set, we have a good triangulation, called the Delaunay triangulation, which satisfies several optimality criteria. Based on Delaunay triangulations, many properties of planar triangulations can be shown, and a graph structure can be constructed for all planar triangulations. On the other hand, triangulations in higher dimensions are much more complicated than in planar cases. However, there does exist a subclass of triangulations, called regular triangulations, with nice structure, which is also touched upon.

After a brief discussion of the demands in meshing for semiconductor process and device simulation, we present a three-dimensional Delaunay refinement technique combined with a modified advancing front algorithm.