Research And Implementation Of Medium-client WebGIS System

Geographic information system (GIS), as the important tools, techniques and disciplines of acquisition, processing, management and analysis geospatial data, has been received wide attention and developed rapidly in recent years. GIS is a marginal discipline integrated with computer-science, geography, remote sensing, mapping, urban planning, land management, urban construction, and many other disciplines and industry sectors.The development of computer technology, space technology and information science, in particular the rapid development of Internet /Intranet technology ,has injected vitality to the traditional GIS and also presented a challenge.Under the traditional GIS model, the disadvantages like geographic data formats incompatible with each other, resources hard to share and so on have seriously impeded the application of GIS in a wide range of industrial sectors. In recent years, with advances of Internet and GIS technology, Internet-based Geographic Information System technology WebGIS has made rapid development. WebGIS not only opened up the new field of the use of geographic information resources, but also provid the possibility of a high degree of social GIS information sharing. At the same time, it also provide a new opportunity for Internet information providers and users, what make Internet users anywhere in the world could be obtain the spatial information that they're interested in.The topics mainly researched how to achieve medium client/medium server model structure of WebGIS based on MapXtreme Java development platform. MapXtreme Java provides three types to develop WebGIS: Thin client/fat server model, fat client /thin server model and medium client/medium server model. The advantage of thin-client model is the smaller volume of network data transmission and the disadvantage is that the lack of interactive with users and poor performance, while the fat client model are highly interactive, but because of the large volume of data transmission, it's hard to transmit on the net. Somewhere the medium client/medium server model is between the upper two models.The paper firstly introduced the associated knowledge of WebGIS and MapXtreme, and further more, researched the working mechanism and communication theory of MapXtremeJava. And then, Combined with relevant projects, researched how to achieve the best interactive performance without increasing the volume of data transmission based on the middle client model,in order to develop a more efficient and more practical WebGIS system.