Research On Methods Of Multi-scale Display For Gis

At present, as GIS moves forward, GIS is widely used in land management, cityconstruction, transportation and many other fields, but there are many challenges inthe research of multi-scale GIS at so far. Multi-scale is hot research area, especially incartography and massive data processing. The cartography of GIS is realized throughselection, simplification, union, replacement and many other operations. And massivedata processing of GIS is realized through reducing the number of points or theprecision. In the research of multi-scale, cartography and massive data processingcannot be separated from each other, so they are short for the method of multi-scaleGIS. In the multi-scale GIS, the selection of method about cartography and massivedata processing directly influences the speed of data processing and the visual effects.In order to improve the speed of data processing and visual effects, so, the research ofmulti-scale of GIS has very important practical significance.In this paper, we did deeply research in multi-scale GIS, and for the shortage weraised two improved methods.In this paper, in order to speed up GIS data processing, we put forward a methodbased on the theory of edge approaching. We use different grids to approach the edgeof object which exists in the map, and if the grid is bigger, the scale of map is bigger.In the contrary, if the grid is smaller, the scale of map is smaller. As a result, weobtain a map in which a big scale map has plenty of information and small scale maphas less information. To solve the problem of data processing and map cartography, inthis paper we proved a method called mixed indexing. The mixed indexing consists oftwo indexes, and one called HHRT index and another called Gap-tree index. TheHHRT index is used for speed up the retrieval of map data, and the Gap-tree is usedfor filling the blank space in the small scale map. Besides, we used topologicaloperators to realize the union of different objects in the paper which based on label.The topological operations based on label can be used for dynamic union.In this paper we proposed two methods, and the first one is called for the realization of multi-scale based on Z values, and another one is called for confusedindex. A large number of experiments show that the methods work well and improvedthe data processing and map visualization efficiently.