Quasi-uniform B-spline Function Using In Digital Terrain Model

From 20 century 50 age later, Digital Elevation Model (DEM) have been adopting and getting infinite attention. It is broadly used in many fields, such as Surveying, Civil Engineering, Geology, Mine engineering, Sight Architecture, Road Design, Prevent or Control Flood, Agriculture, Programming, Military Affairs Engineering, Aircraft and Battlefield Emulate and so on.The theory and technology of the DEM include the technique and means of gathering data, designing data structure, making model, research and putting into practice arithmetic of interpolation, 3D visualization, estimating accuracy, quality control about the DEM, and interrelated computer technology, etc. So far, the above-mentioned theory and technology about the DEM are researched continually.With the rapid development of computer and extensive application of DEM, it is very necessary to find out a modeling method with faster modeling, higher precision and better visualization quality.DEM uses one or more mathematical functions to portray the terrain. This function is usually called interpolation function. If DEM has been built, elevation information of everypoint on the model can be easily acquired. It is similar to geometric modeling very much, so that the DEM surface models can be regarded as surface modeling of terrain. Therefore, we can use the construction methods of free-surface to DEM modeling. At the same time, we also use the construction methods of free-curve in cross-section.The contents researched in this thesis are as follows:1. Combine with the study of terrain surface modeling status in the world, explain the significance of the terrain surface modeling's study.2. Introduce the means of terrain modeling base on two data format—GRID and TIN, summarize the methods and characteristics of terrain surface modeling with three dimensions.3. Because of the data which collected from field works is discrete, it need convert into GRID. So this paper studys the network construction methods of Triangulated Irregular Network earnestly, improves the arithmetic of TIN and realizes the new method based on the VB platform.4. Compare and analyze the interpolation arithmetic which has been put into practice from interpolation accuracy, scope of application, computational complexity and so on.5. Learn construction methods of free-curve (surface) and theoretics of three-dimensional datafield visualization, summarize the merits and properties of B-spline basic function.6. Put the quasi-uniform B-spline curve's construction method into sectional drawing and analysis and evaluation of tunnel cross-section's roughness. Quasi-uniform B-spline is one kind of the free-curve construction methods.7. Using the MATLAB software to carry out the quasi-uniform B-spline, realize the three-dimensional terrain surface modeling and visualization.