Based On Gis Real Terrain Reconstruction System Design And Realization

The Visualization of terrain information in three dimension(3D) has very important and realistic significance in the fields such as military affairs, simulation, virtual reality and geoscience, etc. If we want to emphasize the spacial reality after reconstruct the terrain in computer, we must rely on the Geographic Information System(GIS), which embodied in the aspect such as data source, coordinate definition, spatial query, etc. But most GIS software now deal with the data main still in two Dimension(2D) manner, the appearance of 3D GIS technique extended the working manner of traditional GIS. In other hand, due to the limitation f computer hardware and the large volume of terrain data, the 3D render software dose not support real-time changing and updating the massive terrain data ,so the reconstruct terrain in computer based on GIS has brought challenge to the traditional virtual reality(VR), we must solve the problem such that huge data paging and fluent render when we roam in the scene, etc. Building large scope terrain and the technique of roam has become a hot research topic in virtual reality and 3D-GIS.Besides that, the spatial query which in the 3D GIS condition is a basic function in most of the terrain reconstruct system now, according to this requirement, we must solve the problem of spatial orientation,marking surface features,picking up surface features and design query method and so on. Realizing the spatial query which based on GIS is a function extend to traditional terrain reconstruct system in VR, and is a one of the biggest high lights when GIS has been 3D extended.The following work have been done around the problem:First of all, aiming at the project in our task, did the job of System requirement analysing and collectivity designing for building a 3D terrain reconstruct system which based on GIS. Including choose the data source of terrain reconstruct and the tools for system development.Secondly, based on analysing the well used technique of large scale terrain reconstruction, adopted the technique of partitioning and delamination to pre-manage the rude terrain data, by this to build the static Level of detail(LOD)model, and draw the terrain grid in multi-resolution simplification according to the view dependent judgement rule to enhance the efficiency when rendering terrain. Realized a LOD scene management arithmetic based on the structure of partitioning and delamination of terrain data. And by the help of terrain partition, presented a method which implement the huge terrain data paging to reduce the amount of terrain data which fold to the memory actually, by then to increase the speed of system operation.Besides that, we take the GIS as background, designed and implemented the surface features ploting and basic space to attribute query.Finally ,designed and implemented the scene management module in system.According to the content introduced above, a system of large scale of terrain walkthrough is implemented and it runs well.