Abstract: With the boom of Google Map,Virtual Earth,OpenStreetMap and other free online map services based on Web 2.0,and because of its simple,user-friendly,data-rich,and smooth access,tile map services based on pre-generated techniques are becoming a de facto standard for the new generation of WebGIS,and have posed great challenges to traditional WebGIS.In order to upgrade the WebGIS legacy systems smoothly,and improve the response speed of traditional WebGIS and user experience,this paper designs and develops a tile map service based on middleware technology.Through systematic analysis of its basic principle and system architecture,this paper gives three optimization strategies which are tile spatial index,tiling strategies and the deployment structure.Finally,we make a performance comparison between tile map service middleware and traditional OGC(Open Geospatial Consortium,OGC) standard WMS service.Experimental test data using the world map zoom level 8,under this zoom level there are 32,768 tiles in total,then randomly generated 21,000 request windows which contains 3×3 tiles,and this randomly generated test data are divided into 20 groups,each contains 100 to 2000 request windows successively.We use two kinds of experiments,the first one is sent WMS request directly to a Local GeoServer which hosts WMS services,and the other one is our tile map service middleware which uses multiple threads and simultaneously sends nine tile map requests to TMS middleware.Our experimental results show that comparing with sending WMS request to WMS server directly,the average response time of tile map service reduced by 46%.And the TMS middleware has a high efficiency when cutting map tiles dynamically because of its meta-tiling strategy.The study shows that the tile map service middleware has important application value both in improving traditional WebGIS performance and in upgrading existing legacy systems.

Key words: WMS, tile map service, middleware, legacy system