Research And Implemetation Of WebGIS System Application Based On Ajax

With deepen of the progress of software technology, database technology and network technology; the Geography Information System (GIS) along with its correlative technologies and applications has become the focal point and natural trend of the research. The WebGIS is becoming more and more popular in GIS research areas. AJAX, which based on the browser, is an important programming modal, who can create new powerful application by some mixed technology,.Because of high amount of page views, the consumption of bandwidth brings a serious consequence. The traditional WebGIS encountered bottleneck in performance, scalability, standardization and usability. The server must generate the map image in real-time to response the users' request. As the result of synchronous operation, the waiting time of the users become much longer than ever before, and also the heavy consumption of CPU in server side. The layer, whichever levels system architecture, can't catch the GIS data. It takes too much bandwidth to prevent from the large-scale application of WebGIS.The emphasis of the paper is the research of how to combine the WebGIS with AJAX technology. The paper pointed out a new kind of WebGIS which based on the AJAX technology is more universal and efficient. In view of this, the paper designed a new type of WebGIS System software architecture and hardware architecture. The key features of this model includes: muti-catch, international standard and asynchronous transmission. This paper paid more attention to the key technology in architecture, performance and user interaction.Secondly, by using the WebGIS model which based of AJAX, the operation changed from synchronous to asynchronous. The architecture of system became clearer. We improved the performance of WebGIS and user interaction by using some advanced algorithms, such as non-real time image generating technology, tiled map technology, server based catching technology, images splicing technology, browser based catching technology, asynchronous request technology, and data dynamics overlay technology and so on.Thirdly, the WebGIS engine implemented the GIS standards such as WMS, WFS, and GML and so on, which make different system interoperability become possible. At the same time, this system provided usefiil and flexible AJAX API, which abstracted from complex function of WebGIS, for programmers to rapid construction the system. This system reduced the threshold for application of GIS. And it structured on the J2EE open infrastructure, which can easily extended function and integration with other information services.The final part of the paper introduced the key technology and implemented the system, and evaluated the system's widely used ability via the Internet. And it also raised the prospects for future research.