一种加快WebGIS服务器响应速度的空间索引一种加快WebGIS服务器响应速度的空间索引.doc

一种加快WebGIS服务器响应速度的空间索引( 叶常春+, 罗金平, 周兴铭 (国防科学技术大学 计算机学院,湖南 长沙 410073) A Spatial Index to Improve the Response Speed of WebGIS Servers YE Chang-Chun+, LUO Jin-Ping, ZHOU Xing-Ming (Institute of Computer Science and Technology, National University of Defense Technology, Changsha 410073, China) + Corresponding author: Phn: +86-731-4573664, E-mail: iamdouble@163.com, Received 2003-12-11; Accepted 2004-09-07 Ye CC, Luo JP, Zhou XM. A spatial index to improve the response speed of WebGIS servers. Journal of Software, 2005,16(5):819?826. DOI: 10.1360/jos160819 Abstract: WebGIS servers send digital maps to users. For each request-response round, the servers access map data in batches. The access has a feature called multiscale, that is, the map scales selected by users determine the map detail levels. The access method based on R-tree is not adaptive to the multiscale and batch feature. It has two problems: (1) the data records of features of the same level are not clustered in disks; (2) the granularity of data I/O is too small. So accessing map data for display is unefficient. This paper presents a novel spatial index called Multilevel R-tree, which can solve the two problems. The statistics from experiments show that for range queries, the access method based on multilevel R-tree is much more efficient than the one based on R-tree and can improve the response speed of WebGIS Servers. Key words: WebGIS service; spatial database; access method; spatial index; multilevel R-tree 摘 要: WebGIS服务器向用户提供电子地图浏览服务.每一个请求/响应回合,服务器端都进行着具有多尺度特性的成批式数据访问.多尺度特性是指地图比例尺决定着地图显示内容的详略.基于R-tree的数据访问方法与多尺度性和成批性不相适应,存在“同级要素弱簇聚”和“I/O粒度偏小”两大问题,绘图数据访问效率不高.提出的多级R-tree能够解决上述两个问题.来自实验的统计数据表明,对于区域查询,基于多级R-tree的访问方法的效率明显高于基于R-tree索引的访问方法.使用多级R-tree能够有效地提高WebGIS服务器的响应速度. 关键词: WebGIS服务;空间数据库;访问方法;空间索引;多级R-tree 中图法分类号: TP391　　　文献标识码: A 现今,基于WebGIS,越来越多的Internet用户通过Web浏览器阅读电子地图.WebGIS服务器管理着大型地图数据库,响应用户请求,向浏览器传送背景地图和文字或符号标注.其中,背景地图的数据量占大比重.由于每一个请求/响应回合都有可能传送新的背景地图,所以背景地图发布效率是WebGIS应用的关键指标.本文提出一种能够有效提高Web