Study In Cartography Generalization Of Current Land Use Polygon Based On Fractal Theory

Automatic cartographic generalization has always been the research emphasis in the field of cartography, but also one of the hotspots at home and abroad. Over the years, many people and cartography exerts have been discussed and researched in the field, and achieved a more abundant research results. Among them, the fractal theory is introduced into the automatic cartographic generalization, which provides new ideas and research directions, and the current land-use cartographic generalization has more specific requirements, so it is important that the fractal theory is used in the current land-use cartographic generalization.After studying the basic content and related concepts of the cartographic generalization, the current land-use cartographic generalization and fractal theory as well as the relationships among them, this paper mainly will regard the polygon as the target object, at the same time, discuss how to implement automatic cartographic generalization on the polygon from the quantity selection, structure selection, semantic selection and shape simplification, and put forward a corresponding algorithm later. The specific research idea is to first study the results of previous studies related to the content of cartographic generalization, current land-use cartographic generalization and fractal theory. Secondly, the paper probe into the model of quantity selection, structure selection and semantic selection. Third, the paper discusses in detail the content and characteristics of Douglas-Peucker, a kind of classic compression algorithm. Genetic algorithm is introduced, and the method of getting automatically the initial threshold and the fractal dimension. As well, the idea of polygon contour segmentation is provided based on the relationship between the size of the fractal dimension and the curve structure complexity. Then, the paper take the outline of the land polygon as experiment object in order to verify the effectiveness of the proposed algorithm. Finally, using the ArcGIS for Desktop plug-in programming thought implement the algorithm, and applying the plug-in to deal with the land use polygons of Luochuan County, to complete the cartographic generalization from map scale 1:10000 to and 1:50000.By testing and comparing the experimental results, the paper finds that the cartographic generalization algorithm proposed by the paper can achieve well automatic cartographic generalization of polygonal contours. The algorithm can substantially reduce the points before generalization and have a good compression ratio and high efficiency. At the same time, the algorithm can ensure the structure characteristics of the original image after automatic generalization.