Research On Object-oriented Spatial Entities Vector Model And Its Application

As an emerging information technology for geospatial data collection, management, analysis, presentation and services, geographic information systems (GIS) is capable of handling regional and global geographic data. It has been widely applied in government and business sectors, and has gained very good reputations in geospatial data management, office automation and decision making. With the rapid development of computer networks and geographic information technology, social demands on information systems are increased quickly and the GIS are commonly embedded in general information systems in most government and business sectors. There are three trends in recent GIS projects: (1) mass geospatial data are accumulated and organized in huge databases for quite a few users. (2) Distributed GIS and database technologies are popularly utilized to support enterprise level data management, dissemination and data sharing. (3) GIS are generally integrated with OA, MIS and other information technologies to provide office automation, spatial analysis and decision making.Two challenges are emerging from the broad applications of GIS. The first is how to store, organize and manage large volume of geospatial data efficiently. Another is how to share and utilize the data effectively in business management, decision making and scientific research in networked environment. Considering the distributed GIS architecture and data issues such as data model, structure and database design, this paper introduces an object-oriented spatial entities vector model (OOSEVM) and the data structure for geospatial data. Based on the new data model, a distributed geospatial database system is designed. The mechanism of geospatial data sharing is also discussed. The main research topics include:(1) Object-oriented GIS data modelOn the basis of review, comparison and analysis of existing GIS data models, geospatial representation methods and models of real geographic world are discussed from the perspective of human cognition. The object-oriented approach to data modeling, including the thoughts, methods and techniques, is introduced and lays a solid foundation for database design.(2) An object-oriented spatial entities vector model (OOSEVM)The simple objects, combined objects and classes of spatial entities for OOSEVM are defined. The technical architecture, spatial operation methods are designed for database management.(3) Distributed database design based on OOSEVMThe distributed database management system for geospatial data, consisting of object-oriented spatial data, object methods and spatial metadata, is developed. The mechanism and methods for data organization are analyzed detailedly.(4) Spatial data sharing model based on OOSEVM distributionBased on the existing methods, a distributed OOSEVM for spatial data sharing model was proposed. The object-oriented scheme and object-relationship database management are combined to expand data sharing in networked environment.(5) Application research of distributed spatial databasesBased on the analysis of data requirements and data contents of urban and rural cadastral management in local government, the distributed spatial database is implemented and verified carefully.The research results have been applied to the projects of"Topographic and cadastral mapping & GIS database development for Lingyun county"and"Work-flow customization and comprehensive cadastral management information systems"in Guangxi Zhuang Autonomous Region. The application systems have showed that the OOSEVM, data structure and distributed database designed in this paper are technically feasible, and the data sharing methods are practically effective.