The purpose of this paper is to present a novel three-layer adaptive multisensor data fusion system, which is appropriate to the harsh environment. In order to overcome the noise in the data collected by the sensors in the harsh environment, the first layer of the system is the data pretreatment layer. In this layer, the data collected by the sensor array is denoised by the wavelet threshold algorithm, which provides reliable data to the next data fusion Layer. Taking use of the good error tolerance and self-studying performance of NN (neural network), the data from the first layer is fused by the second layer--- data fusion layer based on NN. The third layer is the feedback layer, in which the output signal is feedback to the second layer. The adaptive algorithm will adjust the weights of the units in the NN, which implements the adaptive ability of the whole system. The experimental results presented in the paper indicate that the system proposed here implements data fusion effectively, its fusion precision is improved compared with the traditional fusion system, and has many advantages like strong adaptive ability, high SNR (signal-to-noise ratio) and low distortion, etc.
With the increasing maturity of distributed object technology, CORBA, .NET and EJB are universally used in traditional IT field. However, theories and practices of distributed spatial database need farther improvement in virtue of contradictions between large scale spatial data and limited network bandwidth or between transitory session and long transaction processing. Differences and trends among of CORBA, .NET and EJB are discussed in details, afterwards the concept, architecture and characteristic of distributed large-scale seamless spatial database system based on J2EE is provided, which contains GIS client application, web server, GIS application server and spatial data server. Moreover the design and implementation of components of GIS client application based on JavaBeans, the GIS engine based on servlet, the GIS Application server based on GIS enterprise JavaBeans(contains session bean and entity bean) are explained.Besides, the experiments of relation of spatial data and response time under different conditions are conducted, which proves that distributed spatial database system based on J2EE can be used to manage, distribute and share large scale spatial data on Internet. Lastly, a distributed large-scale seamless image database based on Internet is presented.
It is the GIS developing direction to integrate GIS with Internet. Internet GIS is not only used to publish distributed geographic information on line, but also to provide on line tools for distributed geographic information real-time analysis and processing. Internet GIS should make use of existing multi-sources and functions for geographic information analysis and processing. The distributed feature is inherent to geographic information, which needs distributed organization and processing approach. Internet GIS (Geographic Information System) is the integration of Internet and GIS, being used to implement publishing on line and distributed real-time analysis of geographic information. The problem of geographic information distributed management and processing should be solved by Internet GIS. This paper provides three approaches to the problem, especially the distributed component and Geo-Connector approach to Internet GIS. The distributed component method includes homogeneous, heterogeneous and conjoint methods, for the problem of distributed geographic information publishing and real - time analysis. With instance, the feasibility and practicability of distributed component method are interpreted in detail. The concept of Geo-connectors in GIS application server side for organization and management of distributed heterogeneous database is presented and a case of heterogeneous geo-data access and interoperability is studied
A systematic plan of building Web Geographic Information System (WebGIS) using ActiveX technology is proposed in this paper. In the proposed plan, ActiveX control technology is adopted in building client-side application, and two different schemas are introduced to implement communication between controls in users¡¯ browser and middle application server. One is based on Distribute Component Object Model (DCOM), the other is based on socket. In the former schema, middle service application is developed as a DCOM object that communicates with ActiveX control through Object Remote Procedure Call (ORPC) and accesses data in GIS Data Server through Open Database Connectivity (ODBC). In the latter, middle service application is developed using Java language. It communicates with ActiveX control through socket based on TCP/IP and accesses data in GIS Data Server through Java Database Connectivity (JDBC). The first one is usually developed using C/C++, and it is difficult to develop and deploy. The second one is relatively easy to develop, but its performance of data transfer relies on Web bandwidth. A sample application is developed using the latter schema. It is proved that the performance of the sample application is better than that of some other WebGIS applications in some degree.
The Virescence Separator of Beijing, the capital city of China, is a virescence zone between the central area and the edge group as well as the zone among different edge groups, within irregular shape and the total area of 240 square kilometers. The construction of the Virescence Separator is a big and difficult project, an effective information system for planning and development with satisfactory performance is therefore essential. In this paper, the applications of remote sensing and GIS (Geographical Information System) technologies in BJVSIS (planning and development Information System for Beijing Virescence Separator), including three dimensional (3D) visualization, integrated databases management and multi-media technologies, were presented. The initial pilot project of BJVSIS was finished successfully in 2001, and up to now this information system runs very well and plays a great role in the construction of the Virescence Separator. Just depended on the applications of so many high-tech like GIS, remote sensing, 3D visualization, and databases integration, BJVSIS can manage all kinds of relevant geographic data, such as vector graphics, DEM (Digital Elevation Model), image and multi-media attributes. And BJVSIS also provides many GIS functions, such as spatial query, 2D/3D display, spatial analysis, statistic calculation, form report and map output.