8 research outputs found

    A Method Using GIS Integrated Voronoi Diagrams for Commuter Rail Station Identification: A Case Study from Brasilia (Brazil)

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    AbstractThis article describes a station location method for a commuter rail system applying a GIS integrated Voronoi diagrams. The method comes from a previously defined track line and considers the stations area coverage. As parameters to define area coverage we first used the point density representing the maximum concentrated activity area. We also use the trip generating rate weights for point density. The method was applied to Brasilia Metropolitan Area, and the final product was a “T” Trunk-Feeder framework that allows an integrated transportation system planning considering others existing transit systems. The stations were classified according to their degree of activities density and its importance for integration. The “T” Trunk-Feeder is a representation of the commuter rail network and the Trunk-Distribution is the transport network responsible for distributing the passengers in central business district - CDB. The proposed model features 69km extension, with the estimated total travel time of 62minutes, and 17 stations being integrated into 2 metro, 4 integrated into LRT stations and 3 integrated into the bus stops

    Minkowski Sum Construction and other Applications of Arrangements of Geodesic Arcs on the Sphere

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    We present two exact implementations of efficient output-sensitive algorithms that compute Minkowski sums of two convex polyhedra in 3D. We do not assume general position. Namely, we handle degenerate input, and produce exact results. We provide a tight bound on the exact maximum complexity of Minkowski sums of polytopes in 3D in terms of the number of facets of the summand polytopes. The algorithms employ variants of a data structure that represents arrangements embedded on two-dimensional parametric surfaces in 3D, and they make use of many operations applied to arrangements in these representations. We have developed software components that support the arrangement data-structure variants and the operations applied to them. These software components are generic, as they can be instantiated with any number type. However, our algorithms require only (exact) rational arithmetic. These software components together with exact rational-arithmetic enable a robust, efficient, and elegant implementation of the Minkowski-sum constructions and the related applications. These software components are provided through a package of the Computational Geometry Algorithm Library (CGAL) called Arrangement_on_surface_2. We also present exact implementations of other applications that exploit arrangements of arcs of great circles embedded on the sphere. We use them as basic blocks in an exact implementation of an efficient algorithm that partitions an assembly of polyhedra in 3D with two hands using infinite translations. This application distinctly shows the importance of exact computation, as imprecise computation might result with dismissal of valid partitioning-motions.Comment: A Ph.D. thesis carried out at the Tel-Aviv university. 134 pages long. The advisor was Prof. Dan Halperi

    LIPIcs, Volume 258, SoCG 2023, Complete Volume

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    LIPIcs, Volume 258, SoCG 2023, Complete Volum

    Collection of abstracts of the 24th European Workshop on Computational Geometry

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    International audienceThe 24th European Workshop on Computational Geomety (EuroCG'08) was held at INRIA Nancy - Grand Est & LORIA on March 18-20, 2008. The present collection of abstracts contains the 63 scientific contributions as well as three invited talks presented at the workshop

    Geometric algorithms for geographic information systems

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    A geographic information system (GIS) is a software package for storing geographic data and performing complex operations on the data. Examples are the reporting of all land parcels that will be flooded when a certain river rises above some level, or analyzing the costs, benefits, and risks involved with the development of industrial activities at some place. A substantial part of all activities performed by a GIS involves computing with the geometry of the data, such as location, shape, proximity, and spatial distribution. The amount of data stored in a GIS is usually very large, and it calls for efficient methods to store, manipulate, analyze, and display such amounts of data. This makes the field of GIS an interesting source of problems to work on for computational geometers. In chapters 2-5 of this thesis we give new geometric algorithms to solve four selected GIS problems.These chapters are preceded by an introduction that provides the necessary background, overview, and definitions to appreciate the following chapters. The four problems that we study in chapters 2-5 are the following: Subdivision traversal: we give a new method to traverse planar subdivisions without using mark bits or a stack. Contour trees and seed sets: we give a new algorithm for generating a contour tree for d-dimensional meshes, and use it to determine a seed set of minimum size that can be used for isosurface generation. This is the first algorithm that guarantees a seed set of minimum size. Its running time is quadratic in the input size, which is not fast enough for many practical situations. Therefore, we also give a faster algorithm that gives small (although not minimal) seed sets. Settlement selection: we give a number of new models for the settlement selection problem. When settlements, such as cities, have to be displayed on a map, displaying all of them may clutter the map, depending on the map scale. Choices have to be made which settlements are selected, and which ones are omitted. Compared to existing selection methods, our methods have a number of favorable properties. Facility location: we give the first algorithm for computing the furthest-site Voronoi diagram on a polyhedral terrain, and show that its running time is near-optimal. We use the furthest-site Voronoi diagram to solve the facility location problem: the determination of the point on the terrain that minimizes the maximal distance to a given set of sites on the terrain

    LIPIcs, Volume 274, ESA 2023, Complete Volume

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    LIPIcs, Volume 274, ESA 2023, Complete Volum

    Combinatorial and Geometric Aspects of Computational Network Construction - Algorithms and Complexity

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    Spatial access to healthcare: exploring the provision of local services

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    This thesis creates a context for exploring the provision of local healthcare services quantitatively, with particular focus on the application of spatial analysis and the use of geographic information systems (GIS). It focuses theoretically on the intersections between: health and medical geography; GIScience and spatially integrated social science; and social justice and spatial equity, elucidating the value of space and place in understanding patient registration with, and usage of, healthcare services. The practical elements of the thesis are based on patient registration data provided by Southwark primary care trust (PCT), and Hospital Episode Statistics from the NHS Information Centre. Focussing initially on primary care, registration with GP surgeries in Southwark is considered firstly from a normative perspective, and subsequently by employing a service area delineation approach. Profiling GP surgeries in this way enables an insight into patient registration behaviours, and sheds light on the challenges of implementing an agenda of patient choice as advocated by recent NHS white papers. The perspective of inpatient and outpatient care is also considered, given the increasing import of joined up provision in primary and secondary care. The thesis considers the linkage between the two service hierarchies, investigating utilisation of secondary care by patients. The value of this thesis derives from its relevance to the reform agenda that looks likely to radically reshape the NHS, the exploitation of patient registration data at individual level, novel use of classification, and the systematic application of spatial analysis across a range of scales
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