Contour Extraction Based On Regular Grid Data

With the rapid development of computer technology, research and drawing of contour are applied to wide areas more and more. Contour extraction is a process that inserts the value in mathematical methods and transforms the point having the same value into map for large numbers of discrete and regular geometric value. It is a powerful tool of analyze characteristics of geographic features that display three-dimensional information in two-dimensional panel. Contour extraction makes a comprehensive analysis simply and intuitively by drawing the corresponding contour, and can grasp the spatial variation of research object. It has been widely used and demonstrates the many advantages in the following areas, terrain simulation, establishment of a hydrological model, highway railway survey and planning, natural resource management and so on.The significance of abstracting the contour is that it mainly transforms the raster data into vector diagram. The raster data is of explicit property and implicit location, while vector data is of implicit location and explicit property. Compare to using vector data, using raster data to express geographic elements is straighter and easy to achieve the composition of multi-layer data, which is also convenient to matching remote sensing images data and scanning data. But the disadvantages of raster data are obvious. When grid side that defines accuracy of data lessens, the number of grid cell grows exponentially. At the same time, it results in increasing storage space. That can lead to more redundant raster data, which makes network analysis more difficult, because of the relevance of adjacent grid cell's property.This paper first analyzed the algorithm in contour generation process, then compares several algorithms on generate contour, describes the advantages and disadvantages of each algorithm. The paper programs in VC and implements reading of grid file, application of grid-based method to track and contour extraction.