Research And Implementation Of WebGIS For Multi-data Sources

The share of heterogeneous and distributed spatial information is the researching hotspot of GIS application recently. It is one of the key problems to solve the differences among the format, structure and semantics of spatial data, and realize the organic integration of multi-data sources. This paper adopts interoperating integration schemas, and solves such problems as the accessing of heterogeneous data, retractility of integrated system, and interoperation of data and so on, by introducing GML, SVG, Metadata and Web Service technologies. Thus it offers some good information services for the users, and realizes the organic integration of distributed, heterogeneous, autonomous, massive spatial information, and in the meantime it improves in evidence the whole performance of the system by introducing the second catching technology.The main research work is as follows:(1) It deeply studies on the data behaving ability and the extending ability of application of GML, analyses the application predominance in the integrated system of multi-data sources of GML technology. According to the status quo of spatial information leaving behind, it discusses the conversion from spatial information to GML data, the parsing and the realizing methods of querying of GML document.(2) On the basis of the deep research on the map behaving ability of SVG technology, it analyses the conversion method of XSLT, and writes the conversion template of XSLT, according to the corresponding relationship between the spatial graphical element between GML and SVG. (3) It researches the working theories of Web Service and Metadata technology, and analyses the application method in the multi-data sources integrated system, thus discusses the realizing methods with which to solve such problems as data assessing and rapid position by the users.(4) It analyses the performance problem of current data integrated system, and puts forward the idea of twice caching for GML document, and then discusses such problems as the management , replacement-policy and coherence of caching module.(5) On the application demand of the city traffic management, it designs and realizes a multi-data sources integrated prototype system, which consists of application layer, data integration layer, service layer and data layer, and each layer is transferred by Web protocol, thus basically realizes the integration of heterogeneous and distributed spatial data, which has high responding performance. According to the analysis of the foundation of prototype system and caching performance, it proves the feasibility of WebGIS of multi-data sources, and offers a new integrated thought for realizing the share of spatial information and integrating large-scale data.