【作者】 胡诚；

【导师】 边馥苓；

【作者基本信息】 武汉大学 ， 摄影测量与遥感， 2013， 博士

【摘要】 目前热门的“数字地球”实现了从二维到三维的跨越,使得三维虚拟地球已经成为一个应用广泛的地理信息公共服务平台。由于目前GIS的发展具有海量数据特征,并且其数据规模还在急剧增加,而客户端受到存储性能限制,大规模场景数据的需求与用户可用的存储空间的矛盾日益严重。在网络环境中,客户端节点与服务器节点之间的连接速度往往受到网络传输和服务器性能制约,同时存在客户端资源的浪费,因此在三维GIS数据场景显示的整个过程中数据传输消耗时间最长。对等网络(Peer to Peer,P2P)虽然不是一项新兴的技术,但是不同于传统集中式模式,是全新的基于对等网络的架构,非常巧妙的将网络中互不直接相连的客户端节点联系在一起,充分利用客户端节点和局部网络传输的闲置资源,将集中式的由服务器到客户端的传输模式转变成为了无等级差别的分布式传输模式。三维GIS可以利用对等网技术显著提升数据传输速度从而提升三维引擎性能。但使用对等网技术依然存在问题,具体表现在采用对等网文件共享的数据组织模型并不适应于三维GIS；离散的数据调度策略导致三维GIS数据加载顺序的随机性,从而影响三维GIS渲染效率和用户体验；GIS缓存更新策略单一未能考虑到对等网共享。本文结合对等网技术实现对三维GIS的优化,针对性的开展对等网环境下的三维GIS数据组织、传输和调度研究,给出系统、完整的研究成果,从而完善和丰富了将对等网技术应用于三维GIS的优化研究。论文主要研究内容如下：1.分析基于对等网技术的三维GIS优化技术的必要性、可行性以及理论依据,并对其相关概念进行阐述；2.根据对等网络中数据传输特点,研究空间数据组织方法,在数据分层组织方面提出参考等级评价机制,在数据分块方面分析组织考虑各种数据类型特点,研究适应对等网传播的分块方式,提出参考数据量的非均匀四叉树网格划分法。3.分析传统三维GIS数据的发布模式,参考典型对等网GIS的组织结构,研究应用于三维GIS的对等网架构的不足,提出优化策略：采用了基于WEB服务的对等网连接方式；采用混合模式的对等网络架构,采用基于位置和内容的节点双向聚类方法分组;对对等网功能采用插件模式设计,提出了基于对等网和KML的地理空间信息服务模型,实现基于对等网技术的简易升级方法。4.参考传统均匀网格数据调度方法,提出非均匀网格快速查询方法。在对等网数据下载过程中强调按重要程度实行分层分块传输,采用下载动态协调策略。采用主动缓存优化技术和对等网节点连接缓存技术预读视点周围场景数据,减少场景漫游的数据等待时间：提出基于热点的主动缓存,增加对等网络中数据备份量;研究三维GIS缓存更新策略,提高对等网整体数据共享效果。5.针对在传统集中式三维地理空间信息服务项目的开发过程中遇到的实际问题,以三维可视化规划管理系统为实例,提出了基于对等网技术的实验性的改进,通过实验对比集中式与对等网式架构的性能差异,指出基于对等网技术三维GIS优化策略可行并且用效。并研究非均匀网格数据划分效果,采用仿真实验验证节点分组效果和主动缓存效果。更多还原

【Abstract】 Currently the "Digital Earth" as a hot issue creates the great improvement from2D vision to3D, and is making the3D vitural earth to be a widely used geospatial information services platform. But the problems between the higher data demond for the large scale scene and the limited store space of the customers, are however becoming more and more serious, while the data size of GIS is growing up. The speed of data transmission from server to customer is limited by many reasons, such as bad network performance and server errors, while the abilities of the peers are not fully pursued. Thus the loading time plays most important role for the scene creation in3D GIS.Peer to peer computing technology is not a new method, but totally different from the C/S mode. It smartly makes the separated peers connected as a whole class and takes fully advantage of the idle resources in the networks, which makes the traditional C/S mode into a equal network, i.e. each peer not only provideds services to others as a server, but also gets benefit from other peers.3D GIS is using the P2P architecture to updata data transmission and the performance of3D. But P2P technology has its problems in many ways, such as unmatched data organization is not suitable for the3D GIS, discreted data transmission disorders the data loading and the GIS data cache strategies is not suitable for the p2p netwok. This paper focus on the topic of optimization strategies for P2P oriented3D GIS, studies the data organization, transmission and schedule. The study presents a more systematic and completed research result, and thus to improve and enrich the geospatial theory and technology about the combination of P2P and3D GIS.The main content this thesis studies is as follows:1. This paper talks about the necessity, feasibility and basic theory to studying P2P based3D GIS optimization and discusses the related concepts.2. Focusing on the characteristic of P2P and3D GIS data, this paper gives the data size based skewed quadtree method to divide the data. Studying the organization, it gives the mehod of chargement for the different data layering, analsises the special characteristic to deblock different type of3D GIS data to fit the requirement of P2P.3. This paper analyses the data distribution of3D GIS, compares the classic network architecture in P2PGIS, and gives optimization strategies to fix the shortcoming: using webservice based method to communicate with other peers,using mixed mode in hierarchical p2p networks, designing P2P plugin to fit the different usage and giving P2P and KML based geospatial information serive model.4. This paper consults data schedule of quadtree method, gives skewed quadtree query method. Then the paper mentions the the strategies of data downloading based on the important degree to arrange the schedule of different type of3D GIS data and the strategies of dynamic coordinating. The paper then takes the active cache method and P2P connection pool to shorten the waiting time and hot block based active downloading to expand the backup of data.5. This paper focuses on the problems of tranditional3D geospatial information services project, gives P2P based method to update the experimental architecture with en example of3D plan and management system. The test of result between C/S and P2P mode shows the advangement in P2P, then the simulation of skewed quadtree and peer group method proves the model.更多还原