Research On The Integration Method Of3-dimentional Terrain Model And Ground Feature Model Based On Level Of Detail

In terms of visual objects, the three-dimensional visualization technology of geographicinformation can be divided into three-dimensional terrain visualization and surface objectvisualization. With the rapid development of the technology in the field of virtual reality,three-dimensional simulation, and computer visualization, the technology of virtualgeographical environments is emerged into these two aspects. And it aims at simulating theenvironment which human survived in at a high accuracy.Though the three-dimensional technology of geographic information has got a hugeprogress, it also faced some challenges, the integration of the terrain model and the groundobject model is one of the challenges. Because of three-dimensional terrain data andthree-dimensional surface feature data are often generated in a heterogeneous environment,which have different data formats, different geographic information parameters, at the sametime the digital terrain itself is only a simulation of the real terrain surface, and it exits someinterpolation errors. So with integration of terrain model and the object model, it will producesome false matching results. In three-dimensional virtual geographical environment, the falsematching results were usually shown as the terrain models are often not located in the correctlocation, which were floating in the air, or drilling in ground deeply. In order to solve theabove problems, and satisfy the accuracy requirement in application of the visualization query,positioning of the three-dimensional geographic information, some improved and optimizedintegration arithmetic are created in this paper. At the same time, to meet the demand ofmodern huge amounts of data, Level of Detail (LOD) technology is brought in this paper.Based on LOD algorithm, and the simulation technology of Open Scene Graph (OSG),first of all, some existing terrain simplification algorithm and terrain integration method weresummarized and analyzed. Meanwhile facing the shortcoming of some existing terrain LODconstruction algorithm, firstly, For the purpose of solving the problem of low visualefficiency, which is caused when loading different level of terrain LOD model, the detailedfeature model is also loaded, then fast visualization methods which based on surface featuremodel simplification is designed in this paper. According to different surface features’geometric characters, such as point surface feature model which is independent of terrain,linear and polygon surface feature model of terrain-dependent, polygon feature model ofterrain-independent, and dynamic surface feature model, different simplify methods aredesigned to match with different level scope of terrain LOD model. Secondly, the terrainsimulation and dynamic loading based on LOD algorithm was interviewed, the same as gridand irregular grid terrain model organization methods. Then, a simplify method of terrain databased on terrain feature points and a terrain LOD schedule algorithm considering terrain complexity is brought out in this paper, which improved the accuracy of terrain simplificationand accelerated the efficiency of data visualization. Finally it focuses on the rules based onirregular TIN and grid under the two different types of terrain data organization mode, theintegration methods of features and three-dimensional terrain model were steeply introducedas terrain-independent point feature integration method, the far point of view under the linearfeature integration approach, under the viewpoint of planar features according to rivers, roads,buildings and the integration method of the dynamic features with terrain.From what described above, and existing researches’ review, ground object modelsimplification methods are designed in this paper, and it is highlights the proposing of aconstruction algorithm of terrain LOD which considered the terrain complexity, andcombining the terrain dynamic loading mechanism to implement the dynamic integration ofterrain and ground objects. At the same time, in view of the existing research focuses on theintegration method based on irregular triangular mesh terrain and object, this paper studies thedynamic scheduling mechanism based on LOD, irregular triangle model and the optimizationof different ground objects model integration algorithm, as well as the rules grid terrain modelwith different form feature model of integrated innovation, improvement of the algorithm.Finally through experiment and simulation in three-dimensional digital visualization platform,the experimental results show that the improved algorithm of this paper not only can meet theaccuracy of three-dimensional integration and the simulation requirements of visualization,and has a certain practicality and stability.