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Virtual Geographic Information System

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VGIS (Virtual Geographic Information System) is a large, multifaceted project to allow navigation of and interaction with very large and high resolution, dynamically changing databases while retaining real-time display and interaction. [1] The system allows users to navigate accurate geographies (less than 1 meter resolution in some cases) with sustained frame rates of 15-20 frames per second. The user can not only see these terrains from any viewing angle but also buildings, roads, high resolution imagery draped on the terrain, and other features. As part of VGIS's 4D symbology capability [2], multiple vehicles, controlled by DIS (Distributed Interactive Simulation) transmissions from sensors or simulations, can move around the terrain. Underlying the system is a queryable GIS database that can be accessed through direct selection in the 3D visualization. The paging, caching, and advanced detail management algorithms allow flythroughs of datasets of any size and extent. [3] In fact the system has been demonstrated using terrain and image data of over 20 GB. There are both VR and workstation- based versions of VGIS and an OpenGL version that will run on a variety of platforms. Among several new capabilities being developed for the system is the capability to automatically generate 3D representations of particular urban areas from 2D road and feature databases.

In order to present terrain data at both high fidelity and high frame rates, we developed an algorithm for real-time level of detail reduction and display of high resolution height field data. [3] The algorithm uses a compact and efficient regular grid representation and employs a variable screen-space threshold to bound the maximum error of the projected image. The appropriate level of detail is computed and generated dynamically in real time, allowing for smooth changes of resolution across areas of the surface. Typically the number of rendered polygons per frame is reduced by two orders of magnitude while maintaining image quality such that less than 5% of the resulting pixels differ from a full resolution image. One future project will be to add the very different organizational detail management to the surface data LOD method. We will then attempt to come up with a scheme that adaptively adjusts both levels of detail to get the best picture of the data.

VGIS can be used anywhere a traditional GIS can be used--and beyond. It can be used for urban planning, evaluations of vegetation, soil, waterway, or road patterns, flood planning, and many other tasks. In addition, the ability to have detailed 3D views and to jump to a different location to check the view opens new possibilities. Planners for new building or other facilities can see full 3D views from their prospective sites or can see the view from nearby existing buildings with their planned facility in plane. Urban planners can see the layout of streets, buildings, and parks on actual topography and can thus evaluate site lines, congestion, where sunlight strikes, etc. In addition, they can use the GIS database to display distributions of commercial activities, where schools or stores are located, where water mains run, and a myriad of other information. Moreover, VGIS provide wireless access for multiply users. Also the Mobile Path Engine can generate optimum path with the lowest risk within a simulated battle field.

The Army has shown great interest in immersive systems like VGIS that can navigate accurate terrains down to one meter resolution. In fact, VGIS has been operated by military personnel at several exercises including the recent joint services exercise at Ft. Bragg, NC. The Navy is also interested in 3D tactical visualization systems, in this case for coastal and shallow water warfare. Finally, a system with immersive capabilities will have enhanced use for training or rehearsal. The military has much interest in training systems for rehearsing battle plans or for exploring and trying out tactical options at the command level. VGIS has also engendered interest for non-military applications.

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