在引入qgf=h后ai的地图符号由拓扑变换被表示为h(ai)。地图投影是从球面S到二维平面Z的拓扑变换，地图符号的位置信息通过地图投影获得。地图符号在地图平面上有一个基本的表示空间mind，它在制图区域A上的原象h-1(mind)限制了地物的尺度。为达地图可视化的目的，点线符号必须实行制图夸大。点线符号属于闭集，而面状符号属于开集，它们具有互补关系，因此，点线符号的夸大必然使面状符号缩小。地图符号蕴含着投影变换，夸大和缩小变换。%After lead intoqgf=h the map symbol ofaiwas showedh(ai) by topological transformation. Map projection is the topological transformation from spherical surface to the two-dimensional plane Z, the location information of map symbol was got by map projection transformation. Map symbol have a basic showed spatial on map plane and its inverse imageh-1(mind) on mapping area a limited the measure of geo-object. Because of aim of map visualization must take cartographic exaggeration for the point and line map symbol. The point and line map symbols belonging to closed set and the area map symbols belonging to the open set, they possess of complementary set relation each other, thus, because of the exaggeration of point and line symbol must lead the contract of area symbol. The map projection, exaggeration and contract transformation are implicated by map symbols.
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