Generally, the main part of the total information and content expressed by a map is related to relief, so the rational terrain expression on 2 dimension is greatly significative and important to the information expression and transmission of maps. 在一幅地图中,地貌通常占了整个图幅极大部分的信息内容,所以科学合理地在二维空间上表示地形对地图信息的表达传输能力有着重要的影响。