Key Technology Of Digital Seabed-WebGIS System Design

As a part of Digital Earth, Digital Seabed Technology Bohai Oilfield Representative Area Construction is a project of the National '863' Plan. Researching and developing Digital Seabed Web-based Geographic Information System (WebGIS) is one of the difficulties and key technologies of the project.Having studied the technologies which are used to implement WebGIS, analysed the similarities and differences among the several popular WebGIS platform software, and considered the system requirement of Digital Seabed, the author chose ArcIMS (a product of ESRI Corporation) as WebGIS platform software. On the basis of the researches, the author has completed system design, database design and function design of the WebGIS. The main function has been implemented and passed the preliminary test.According to the types of map data communication between client and server, the model of WebGIS is divided into raster map model and vector map model. Each of them has several implementing methods, the former includes CGI (Common Gateway Interface), Server API, Servlet, and the latter includes Plug-In, Java Applet, ActiveX and so on. Because there is no technology can be used to resolve all the problems of WebGIS, it is necessary to integrate them to get better performance.In the meantime, the author also investigates other technologies about implementing WebGIS, such as Java, XML (extensible Markup Language), SVG (Scalable Vector Graphic), ArcSDE spatial database, metadata management, etc.The distributed database, spatial database and UML (Unified Modeling Language) technologies have been studied. As for the database of WebGIS, the author designs the database with the model combined the advantages of distributed database and centralizeddatabase, so the model can solve the conflict between the public data that can be accessed entirely and the private data that can only be accessed within the client's corporation. Having studied the technologies of storage, spatial index and spatial query about spatial database, the author designs the spatial database of Digital Seabed with the ArcSDE technology. The object-oriented database model with UML, which is of advantage to illustrate complex relationship among the objects, can remedy the disadvantages of Entity-Relationship Model. The author applies the above method to improve the database design.