A Technical Investigation Of The Virtual GIS And Its Prelimilary Application

The work presents a thorough discussion on the building a virtual geo-environmental information system (VRGIS) and the implementation of the preliminary functions of information management, query and analysis based on virtual geographical environments. And the preliminary functional VRGIS is applied to western Jilin Province for the purpose of evaluation and monitoring the land-use and land cover change.A weak point of any given GIS at the present is that it does not have adequate ability in visualization. With the development of the Virtual Reality (VR) technology, a new method was brought forward which is to apply the VR technology to GIS. Virtual Reality is a new technique developed on the end of 20th century. It has been defined as a way for humans to visualize and manipulate extremely complex data, and interact with computers. Many people find it difficult to visualize the data represented by a GIS. However, VR promises an environment, which fully engages all the users' senses and provides full interactivity in real time. Virtual environments provide greater immersion into the world or environment of scientific data, thereby enhancing the researcher's perception of its features and forms. It is our attempt to integrate VR and GIS technologies to discover more information out of available data. GIS manages its huge, complex terrain and GIS data sets at real time rates in an efficient manner by using hierarchical spatial data structures. Virtual Reality adds an important freedom for the user to visualize and interpret spatial data more effectively. The functional module and framework of the system is analyzed and designed. The system is divided as data management subsystem, virtual geo-environments visualization subsystem, and spatial query & analysis subsystem, and special application subsystem. Virtual geo-environments building is based on the development of computer technology, the appearance of high-powered graph workstation and the creation of real sensing graph algorithmic. The progress of building virtual geo-environments is a digital-modeling to terrain and relief, the result is Digital Elevation Model (DEM).This paper introduces a multi-source information model after studying the basic theory and key technology of DEM and the present study of GIS 3D model. The system was developed with the Interactive Data Language (IDL), which is the fourth generation programming language. Because it is easy to learn and has abundant functions and can produce satisfactory result, IDL is the ideal software to develop Virtual Reality module, which is object-oriented. The development of the system makes use of many computer techniques including real sense computer graphic technique, scientific visualization technique and so on. It is important to study how to present the special GIS data in the virtual geo-environments.The system has been applied to the western Jilin Province. The system establishes the virtual environments of every county in the study area. The environments are simulations of the real world supported by a GIS. And users can operate in the environments, such as walking in the environments at will. The land-use is one of the most important factors causing the entironmental changes, which is the interactional result by all kinds of subsystems of the entironment. The preliminary VRGIS system developed in this work can be used to analyze the land use changes and to provide a useful aid for the protection of the environmental.