The Digital Elevation Modeling And Data Visualization,

With the rapid development of computing technology and geographic information systems (GIS), digital elevation model (DEM), as a digital description and simulation of the surface topography, has become one important component of spatial data infrastructure and "Digital Earth". For decades, the study of digital elevation models is always very active. So, this paper researches how to establish a digital elevation model and realize its visualization. The Grid-DEM has many advantages, such as calculating method is simple and effective, and the structure easily matches the one of remote sensing data and so on. So it has been regarded as one of the most basic and most important models in DEM.This paper mostly researched on the algorithm of generating Grid-DEM from discrete sampling points in the condition of existing constrained borders, the algorithm of generating contours from this Grid-DEM, and the algorithm of smoothing contours and the algorithm of generating light and shade contours.In the project of compute mine, this paper encounters a problem that the date of discrete sampling points existed constrained borders. This region located in the constrained borders is the researched region. So, establishing Grid-DEM in this condition is different with the one in the common condition. It only needs to calculate the Grid-points that located in the researched region and give other points a particular value to distinct. Because these points that were not in the region are not used in the following research. However, if every point were judged whether it is in the region, it will be very trouble. So, this paper only judged these points that were near the constrained borders whether it is in the region by two reference points. Finally, it establishes the Grid-DEM in the condition of existing constrained borders and provides the date base for terrain research.In the Grid-DEM that existed constrained borders, the currently used algorithm of generating contours from Grid-DEM has some problem in calculating contour-points in the borders. Considering this problem, this paper proposes a new algorithm of tracing contours. It simplified the process of tracing contours to doing it in each grid and it also can draw contours in the borders.About the algorithm of smoothing contours and the algorithm of generating light and shade contours. This paper introduced how to use tension spline function to resolve the issue of smoothing contours and realizing drawing light and shade contour.