Probe into Key Techniques of Regional-Oriented 3D GIS

Regional Geological Information System combines the multi-dimensional and dynamic spatial information into an integrated spatial information system. 3D geological modeling and its preprocessing or post-processing are the most difficult problems for constructing the system. Based on the current 3D GIS technique, some basic problems in establishing the system are discussed in this paper, including 3D spatial data model, 3D geological modeling, and visu- alization of 3D geological data. A kind of 3D vector data model based on boundary representation for geological object and its topology was developed in order to model and visualize complex geological structures. In addition, some key techniques are pointed out for further study.

THREE DIMENSIONAL DATA STRUCTURE AND DATA MODEL

3D GISs were developed simultaneously in the late 1980s in a number of different disciplines.The development of these 3D GISs can not yet meet all needs for new representations and analytical tool s in 3D envir onments.In this paper,the data structures,especially solid-based data representa tions are introduced.Then,a typical object-oriented data model is put forth to s how a new data model.And at last,two data access methods are proposed to make th e data model clear.

3D Road Network Modeling and Road Structure Recognition in Internet of Vehicles

Internet of Vehicles (IoV) is a new system that enables individual vehicles to connect with nearby vehicles,people, transportation infrastructure, and networks, thereby realizing amore intelligent and efficient transportationsystem. The movement of vehicles and the three-dimensional (3D) nature of the road network cause the topologicalstructure of IoV to have the high space and time complexity.Network modeling and structure recognition for 3Droads can benefit the description of topological changes for IoV. This paper proposes a 3Dgeneral roadmodel basedon discrete points of roads obtained from GIS. First, the constraints imposed by 3D roads on moving vehicles areanalyzed. Then the effects of road curvature radius (Ra), longitudinal slope (Slo), and length (Len) on speed andacceleration are studied. Finally, a general 3D road network model based on road section features is established.This paper also presents intersection and road section recognition methods based on the structural features ofthe 3D road network model and the road features. Real GIS data from a specific region of Beijing is adopted tocreate the simulation scenario, and the simulation results validate the general 3D road network model and therecognitionmethod. Therefore, thiswork makes contributions to the field of intelligent transportation by providinga comprehensive approach tomodeling the 3Droad network and its topological changes in achieving efficient trafficflowand improved road safety.

A star-based data structure to store efficiently 3D topography in a database

For storing and modeling three-dimensional(3D)topographic objects(e.g.buildings,roads,dykes,and the terrain),tetrahedralizations have been proposed as an alternative to boundary representations.While in theory they have several advantages,current implementations are either not space efficient or do not store topological relationships(which makes spatial analysis and updating slow,or require the use of an expensive 3D spatial index).We discuss in this paper an alternative data structure for storing tetrahedralizations in a database management system(DBMS).It is based on the idea of storing only the vertices and stars of edges;triangles and tetrahedra are represented implicitly.It has been used previously in main memory,but not in a DBMS.We describe how to modify it to obtain an efficient implementation in a DBMS,and we describe how it can be used for modeling 3D topography.As we demonstrate with different real-world examples,the structure is compacter than known alternatives,it permits us to store attributes for any primitives,and has the added benefit of being topological,which permits us to query it efficiently.The structure can be easily implemented in most DBMS(we describe our implementation in PostgreSQL),and we present some of the engineering choices we made for the implementation.

A ubiquitous knowledgeable data representation model(UKRM) for three-dimensional geographic information systems(3D GIS)

In the face of complicated, diversified three-dimensional world, the existing 3D GIS data models suffer from certain issues such as data incompatibility, insufficiency in data representation and representation types, among others. It is often hard to meet the requirements of multiple application purposes(users) related to GIS spatial data management and data query and analysis, especially in the case of massive spatial objects. In this study, according to the habits of human thinking and recognition, discrete expressions(such as discrete curved surface(DCS), and discrete body(DB)) were integrated and two novel representation types(including function structure and mapping structure) were put forward. A flexible and extensible ubiquitous knowledgeable data representation model(UKRM) was then constructed, in which structurally heterogeneous multiple expressions(including boundary representation(B-rep), constructive solid geometry(CSG), functional/parameter representation, etc.) were normalized. GIS's ability in representing the massive, complicated and diversified 3D world was thus greatly enhanced. In addition, data reuse was realized, and the bridge linking static GIS to dynamic GIS was built up. Primary experimental results illustrated that UKRM was overwhelmingly superior to the current data models(e.g. IFC, City GML) in describing both regular and irregular spatial objects.

Unified Data Model of Urban Air Pollution Dispersion and 3D Spatial City Model:Groundwork Assessment towards Sustainable Urban Development for Malaysia

Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution is one of the indicators headed towards it. At present monitoring and managing air pollution in urban areas encompasses sophisticated air quality modeling and data acquisition. However, rapid developments in major cities cause difficulties in acquiring the city geometries. The existing method in acquiring city geometries data via ground or space measurement inspection such as field survey, photogrammetry, laser scanning, remote sensing or using architectural plans appears not to be practical because of its cost and efforts. Moreover, air monitoring stations deployed are intended for regional to global scale model whereby it is not accurate for urban areas with typical resolution of less than 2 km. Furthermore in urban areas, the pollutant dispersion movements are trapped between buildings initiating it to move vertically causing visualization complications which imply the limitations of existing visualization scheme that is based on two-dimensional (2D) framework. Therefore this paper aims is to perform groundwork assessment and discuss on the current scenario in Malaysia in the aspect of current policies towards SUD, air quality monitoring stations, scale model and detail discussion on air pollution dispersion model used called the Operational Street Pollution Model (OSPM). This research proposed the implementation of three-dimensional (3D) spatial city model as a new physical data input for OSPM. The five Level of Details (LOD) of 3D spatial city model shows the scale applicability for the dispersion model implementtation. Subsequently 3D spatial city model data commonly available on the web, by having a unified data model shows the advantages in easy data acquisition, 3D visualization of air pollution dispersion and improves visual analysis of air quality monitoring in urban areas.

Cross-Verification of As-Built Point Cloud and GIS-Related Map Data

This study cross-validates existing urban maps using point cloud models to update GIS related data. The model, as-built 3D data, is created to integrate with maps in an architectural CAD platform. The clouds are referred by existing vector maps to verify inconsistency and to update 3D spatial relationships between subjects and environment. The cloud model shows its top reference hierarchy as the updated data for topographic-derived urban maps.

三维GIS的基本问题探讨

回顾与评述了三维 GIS的相关发展情况 ,探讨了三维 GIS的有关基本问题 ,如数据获取、大数据量存贮与处理、三维空间分析 ,同时指出科学计算可视化、数据库系统管理、数字影象处理等技术的成熟和二维 GIS长期发展提供的理论实践经验等为三维 GIS的发展提供了良好的基础 .最后为三维 GIS实际系统的开发提出了几个值得注意的要点 .

一种三维GIS矢量数据结构的研究——以矿山应用为例

本文针对传统数据结构的不足，借鉴二维矢量数据结构，并结合矿山实际情况，提出了用六组拓扑结构来刻划：点－结点，弧，环，曲面，体域和复杂地物之间的拓扑关系。引入“层次树”来动态维护这六组拓扑结构。最后针对一典型的矿山实体，给出了基于这六组拓扑结构的完整描述。实践证明：用本文所提出的六组拓扑结构能够很好地刻划出矿山实体的特点，“层次树”的引入则可大大减少数据维护所需的辅助操作。

三维GIS的线性八叉树数据结构研究

本文在分析和比较了三维ＧＩＳ中多种数据结构的基础上，重点讨论了线性八叉树编码原理、线性八叉树数据结构以及线性八叉树的生成、显示与操作，并从数据结构的优缺点着眼，提出将ＢＲ 法与线性八叉树相结合的观点；从三维动画技术着眼，提出将原型法、ＣＳＧ 法与线性八叉树相结合的观点。

三维位置定义(3D-LD)系统模型研究

对以建筑物为三维背景空间的物体对象的3维位置定义(3D-LD)管理进行了深入分析,研究了3D-LD数据特征,分析了3D-LD关键要素模型的生成方法,给出了3D-LD三维场景的两种组织方式,并最终给出适合当前软件编程技术的系统实现方法。

基于GIS的虚拟泰山三维可视化系统研究

本文阐述了GIS、虚拟现实、三维可视化等技术在国内外的发展和研究现状,提出了本系统需要解决的问题,建立了虚拟泰山三维可视化数据模型,论述了虚拟系统的功能及应用,并分析了系统的应用前景和经济效益.

基于GIS构建村庄3维模型的方法研究——以广州市萝岗区九龙镇汤村规划为例

利用MapInfo软件实现地形空间数据在CAD与GIS软件之间的格式转换,通过ArcView3.2软件平台,建立3维数字模型,以广州市萝岗区九龙镇汤村新农村规划为例,构建村庄的3维景观模拟环境,为新农村规划提供参考。

基于三维GIS技术的地震监测系统分析演示平台设计

针对目前地震系统在监测数据无法详细立体展现的缺点,本文在传统2D-GIS技术的应用基础上,将3D-GIS技术引入地震相关数据的处理中,设计出一款基于3D-GIS技术的地震监测系统分析演示平台。通过分析3D-GIS技术的数据处理原理,给出地震监测系统分析演示平台的总体方案,并详细说明了系统基本组成的功能,给出数据库数据引用规则及数据应用指标。最后应用所设计的3D-GIS技术的地震监测系统分析演示平台,对所采集的实际数据进行处理并给出了实际效果图。

东非大裂谷的地壳和上地幔密度结构

利用卫星重力场数据和小波多尺度分析方法对东非大裂谷进行三维密度结构成像,取得了东非大裂谷地壳和上地幔多个深度等效层上的密度扰动图像,为东非大裂谷岩石圈结构和动力学的研究提供了重要佐证。结果表明,东非大裂谷中段的西支裂谷与东支裂谷的幔源熔体同源,但是西支裂谷发育较不充分、形成较晚。东非大裂谷的动力学模式为熔流体上涌的树形分叉模式,其要点包括:(1)低密度流体在软流圈大面积上涌;(2)流体在岩石圈继续上涌,部分转化为基性岩浆岩,平面面积缩小;(3)进入地壳后上涌熔流体分叉成多支,平面总面积进一步缩小;(4)熔流体上涌到上地壳后仅在裂谷带活动,反映为火山链和玄武岩带。

应用Supernatural GIS进行3维城市数据分区管理的方法研究

探讨了3维城市数据管理的有关问题,基于3维GIS软件Supernatural GIS研究了3维城市模型大场景海量数据的分区管理、动态调度和快速显示问题,提出了应用Supernatural GIS实现城市3维可视化及大范围城市景观动态漫游的解决方案。

An approach for converting orthographic projection drawings into 3D-CAD models

Abstract： Hand drawings and two dimensional （2D） CAD drawings have been replaced by three dimensional （3D） CAD models in mechanical design, but some 2D drawings produced before are needed in the new design. However, the techniques and software packages for automatically converting 2D drawings into 3D-CAD models with high precision have not yet been developed due to the difficulties to verify the validity of the drawings, to decide the hidden lines and eoncavo-convex faces, and to represent free-form surfaces. In addition, it is very time consuming to manually convert a large number of 2D drawings into 3D CAD models. To address these problems, we propose an approach for converting 2D drawings into 3D-CAD models automatically.

三维GIS模型技术问题探讨

探讨了由二维ＧＩＳ扩展到三维ＧＩＳ的必要性及可行性，讨论了矿山、地质工作中对三维ＧＩＳ工具的基本要求，分析了三维ＧＩＳ工具研制中必须解决的技术难点，讨论了三维ＧＩＳ的数据结构，以及矢量结构的三维ＧＩＳ与三维拓扑关系。

A 3-DIMENSIONAL DATA MODEL FOR VISUALIZING CLOVERLEAF JUNCTION IN A CITY MODEL

The research work has been seldom done about cloverleaf junction expression in a 3-dimensional city model (3DCM). The main reason is that the cloverleaf junction is often in a complex and enormous construction. Its main body is bestraddle in air,and has aerial intersections between its parts. This complex feature made cloverleaf junction quite different from buildings and terrain, therefore, it is difficult to express this kind of spatial objects in the same way as for buildings and terrain. In this paper,authors analyze spatial characteristics of cloverleaf junction, propose an all-constraint points TIN algorithm to partition cloverleaf junction road surface, and develop a method to visualize cloverleaf junction road surface using TIN. In order to manage cloverleaf junction data efficiently, the authors also analyzed the mechanism of 3DCM data management, extended BLOB type in relational database, and combined R-tree index to manage 3D spatial data. Based on this extension, an appropriate data

浅议3维GIS基础数据获取的若干问题

随着科学技术的进步和应用的深入,人们已不再满足于2维GIS,而开始转向研究能真实反映客观自然空间的3维GIS。3维GIS的发展既存在有利因素,也面临必须克服的困难。3维空间数据的获取是3维GIS的基础,本文讨论了3维数据在采集、编辑、检查的生产过程中遇到的一些典型问题。