Three-Dimensional Visualization And Spatial Analysis Of Dynamic Pollution Migration Process In Xiangjiang River

Xiangjiang River, as the largest river in Hunan Province, is not only a major drinking water source basin, but also a crucial lifeline for economic and social development in Hunan Province. In recent years, the emission of massive industrial and domestic waste causes the water quality of Xiangjiang River getting worse and worse, and it’s increasingly urgent for the demands to carry out a research on three-dimensional visualization and spatial analysis of dynamic pollution migration process in Xiangjiang River. However, the current simulation of dynamic pollution migration still concentrates on the one-dimensional and two-dimensional situations, while the study on three-dimensional simulation is still on its theoretical model which is difficult and complex to be solved and visualized.The two-dimensional river is always studied as the object to complete three-dimensional pollutant migration simulation through assigning the elevation to the two-dimensional river with the DEM data, which brought the impossibility to understand the internal situation of pollutant migration under the river. Therefore, using the pollutant in Xiangjiang River as the research object, the paper has derived the three-dimensional water quality model of Xiangjiang River and the model’s analytical solution by simplifying the basic model on pollutant migration, according to the theoretical analysis on basic forms of the motion of pollutants in water and the research on the actual situation of Xiangjiang River.About three-dimensional visualization on pollutant, the paper has explored its solutions from three aspects with GIS technology by taking into account the advantages of GIS such as the expression of dynamic spatial relations, spatial correlation function, massive data processing, three-dimensional display and dynamic simulation. The three aspects are three-dimensional visualization on the river, three-dimensional visualization on riverbed and three-dimensional visualization on auto-mapping profiles.In view of the three-dimensional visualization on the river, the paper has studied a method to extract river grid along the centerline of the river, and has assigned the elevation of the river grid with inverse distance weighted interpolation (IDWI) method, with the target to reflect the actual environment of the river and facilitate computer processing. In order to establish more realistic three-dimensional model of riverbed, the discrete points along the centerline of the river has been extracted with a method that shares the similar thought of the river grid method. With discrete points, elevations have been assigned by the Lagrange interpolation, and those results have been used for the elevations interpolation of DEM regular gird with kriging interpolation method to establish the riverbed’s DEM. Meanwhile, in order to show the internal side of the pollutants’migration situation, the paper has realized a way to generate river profile automatically, thus an approach has been provided to observe dynamic pollution migration process under three-dimensional environment in a real sense.In addition, based on the discussion of the integration ways between pollutant migration model and GIS, the paper has achieved a new code-based calculation method on reference coordinate. Compared with the traditional coordinate rotation methods, the new method has established and overlaid multiple reference coordinate systems according the actual position, which not only is easier to realize, but also is able to solve the uncertainty of the reference coordinate system on island that make simulation results more accurate and reasonable.Based on GIS/Computer/Database technology, taking ArcSDE as the spatial database engine, Oracle as the backstage database, VS2008as the development environment, ArcGIS Engine9.3as the development component, the paper has developed three-dimensional visualization and spatial analysis system of dynamic pollution migration process on the C/S pattern. And the paper also has used the actual data of Xiangjiang River to simulate the effect of pollution migration, and realized the integration between pollution migration model and three-dimensional scene. The result shows that the system can be applied to actual situation, and provide a new thought and reliable technical support for three-dimensional water quality simulation.