基于瓦片数据的WebGIS三维可视化研究

发布时间：2018-05-05 06:48

本文选题：三维WebGIS + 金字塔结构　；参考：《东华理工大学》2017年硕士论文

【摘要】：从二十世纪开始,网络技术进入了快速发展阶段,网络普及程度以及网络的速度都有了明显的提升,以此基础为WebGIS的发展提供了坚实的技术保障。因此,基于B/S结构的GIS系统正在逐渐占有传统GIS的市场。另一方面富客户端应用、动态网页等技术的诞生和成熟化,使B/S系统与C/S系统在效果和功能上的差距越来越小。然而在移动设备上目前基于WebGIS的地图应用基本都是桌面应用客户端模式,很少运用简单的浏览器实现功能。一方面由于移动设备,无线网速等硬性条件的限制,另一方面从浏览器实现地图应用功能上不能做到尽善尽美。传统的三维GIS客户端不能充分满足开放性、跨平台性,而且比较依赖插件。因此将三维WebGIS平台构建为开放、跨平台、免插件的模式,对于三维Web GIS发展具有重要意义。本文通过对B/S结构下RIA应用模式的研究,总结分析了在该模式下的地理信息系统的发展状况和优缺点。针对RIA模式的主要问题,文本采用近年来兴起的HTML5标准并结合AJAX动态网页技术,在canvas显示模型采用WebGL技术的可视化路线,并在以下两个主要方面做出了系统模块的优化:(1)在瓦片数据的储存传输方面,采用了金字塔结构的储存方式,建立了专门针对空间的数据传输的四叉树索引机制;为了提高用户操作流畅性,针对浏览器的缓存技术,设计编程了瓦片数据的预取策略与HTTP缓存策略。(2)在地图可视化渲染阶段,根据Web GL图像可视化标准,利用顶点缓存技术简化了可视化数据的调度过程;在纹理可视化部分,基于用户的视觉要求和显示效率,采用了Mipmap纹理映射机制;分析常用的可视化剔除方法,针对大量的三维模型设计了一种适用于虚拟地球的切面剔除方法。(3)在最后阶段,本文基于Cesium开源JavaScript库,并根据应用需求设计实现了具有易部署、跨平台等优点的WebGIS平台。经过测试,本文设计的WebGIS平台可以在PC端与移动端均可稳定运行,达到了预计的效果。
[Abstract]:From the beginning of the 20th century, the network technology has entered the stage of rapid development, the popularity of the network and the speed of the network have been obviously improved, which provides a solid technical guarantee for the development of WebGIS. Therefore, GIS system based on B / S structure is gradually occupying the market of traditional GIS. On the other hand, with the birth and maturity of rich client application and dynamic web technology, the gap between B / S system and C / S system in effect and function is smaller and smaller. However, the current map applications based on WebGIS on mobile devices are basically desktop application client mode, and rarely use simple browser to realize the functions. On the one hand, due to the limitations of mobile devices, wireless network speed and other hard conditions, on the other hand, the realization of map application function in browser can not be perfect. The traditional three-dimensional GIS client can not fully meet the open, cross-platform, and more dependent on plug-in. Therefore, it is of great significance for the development of 3D Web GIS to construct 3D WebGIS platform as an open, cross-platform, plug-in free model. Based on the research of RIA application mode based on B / S structure, this paper summarizes and analyzes the development status, advantages and disadvantages of GIS in this mode. Aiming at the main problems of RIA mode, the text adopts the HTML5 standard which has arisen in recent years and combines with the AJAX dynamic web page technology, and adopts the visualization route of WebGL technology in the canvas display model. And in the following two main aspects of the optimization of the system module: 1) in the storage and transmission of tile data, the pyramid structure is used to store the data, and the quadtree index mechanism for spatial data transmission is established. In order to improve the operation fluency of users, the prefetching strategy of tile data and the HTTP cache strategy. 2) are designed and programmed according to the Web GL image visualization standard in the stage of map visualization rendering. In the part of texture visualization, Mipmap texture mapping mechanism is adopted based on the user's visual requirements and display efficiency, and the common visual culling methods are analyzed. Aiming at a large number of 3D models, this paper designs a method of cutting out for virtual earth. In the final stage, based on the open source JavaScript library of Cesium, this paper designs and implements a WebGIS platform with the advantages of easy deployment and cross-platform, according to the requirements of the application. After testing, the WebGIS platform designed in this paper can run stably on PC and mobile, and achieve the expected effect.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P208

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