本文讨论了一种负载均衡的Web空间数据发布和地理分析平台的实现(LreisServer),并通过不同的数据源对其性能进行测试。该平台遵循OGC服务标准,并已实现WMS,WFS,GML规范。本文从互操作的角度论述了WMS,WFS,GML扩展模块的实现细节。系统后端采用PostGIS为空间数据库,依靠其强大的矢量栅格空间数据格式存储能力,为互操作式在线空间分析系统提供了有力的数据支撑和空间查询支持。系统前端采用Openlayers与Activex控件动态结合的方式,利用C#和ASP.NET实现地图展示和基本胖客户端的空间操作。地理分析系统几何要素实现OGC简单要素标准,算法实现包括buffer、overlay等,空间索引支持四叉树、R-tree等索引。系统设计实现一种ASP.NET地图服务缓存机制,可以实现历史数据的回溯,加速地图客户端的显示和互操作。试验结果表明该平台能很好地完成以下功能: (1)提供高质量和高效率的WMS地图服务;(2) 可以利用PostGIS强大的空间存储和分析能力,提供空间数据服务和GML服务;(3)通过负载均衡策略完成简单的客户端空间分析功能。

Recent advances in internet technologies, coupled with wide adoption of the web services paradigm and interoperability standards, make the World Wide Web a popular vehicle for geo-spatial information distribution and online geo-processing. In this paper, a new spatial computing and data service publishing platform, i.e. LreisServer, is designed and implemented. The platform complies with OGC specification and implement WMS, WFS, GML standards. The extension implement details are discussed through a cooperation perspective. In the backside this platform takes postgis as spatial database and applys its powerful ability to analyze and query spatial data. In the frontside, RIA technology such as openlayers and active is hybrid used, and use c# asp.net to display map and couple with fat client spatial operation.The geometry objects model in this platform comply with OGC simple feature specification (point, polyline, polygon), and has map project function, including algorithm buffer, overlay, etc. The spatial index implement quardtree, R-tree, etc. A new kind of map cache mechanism is designed and developed to help speed up historical map data showing and accelate interoperation on the client side. Unit test is done with different data sources on this platform. In this papaer we also evaluate alternative approaches and assess the pros and cons of our design and implementation. The results showed that: (1)because of the aps.net cache tool, this platform can have a better performance in WMS service than ordinary OGC WMS. (2)On the benefit of spatial data storage and operating functions in Postgis, LreisServer can provide spatial data service and raw data in GML format. And (3)using the loading balance strategy, LreisServer can do simple spatial process and analysis on the client side.