一种加快WebGIS服务器响应速度的空间索引

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.

A Spatial Index to Improve the Response Speed of WebGIS Servers

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.