Design And Implementation Of Web-based Vector Map Server System

The web-based Geographic Information System has been used as a popularinformation tool, which is the combination of the GIS and the Internet technology.Most existing web-based Geographic Information Systems use raster data which islimited on zoom level and complex query. Further research on vectorized map data isdone to deal with the problems above, and a web-based vector map server prototypesystem called WebMap is designed and implemented.The vector map data can be rendered into the raster map data by the WebMapsystem so it can be presented to the user with a browser. The vector map can bezoomed, roamed, queried, marked, layer selected and projection easily, and it hascontinuous zooming level.This paper focus on the following aspects:1. The common Web-based Geographic Information Systems were studied andanalyzed, then the framework of the WebMap is designed;2. The storage and indexing capabilities of the spatial data which is managed bythe relational database PostgerSQL are analyzed to solve the storage and indexingissues of the vector map data. The clustering and synchronizing of databases areimplemented;3. Reverse-proxy technology of the Nginx is studied. The configuration and loadbalancing of the application servers were implemented with the support of Nginx;4. I/O completion port model is used to implement the process of the user‘srequests in the Application Server instead of the normal methods;5. A problem may occur by the Application Server cluster, which is that the samerequest may be send to the different Application Servers when it is send the secondtime. So as to cause repeated rendering work. In this paper, a secondary caching servercluster method was proposed to resolve the problem. The consistent hashing algorithmwas studied and implemented for the cache server cluster to accelerate the responsingspeed.The experimental result of the prototype system shows that the whole system canmeet the Expectations. And the secondary caching server can obviously improve theresponsing speed and the concurrency performance.