比例因子必须能够提供可协调的全局空间，或全屏幕或是调用视窗视图。
The scale factors must enable the presentation of the coordinated global space or the full-screen or window view.
选定比例，该比例允许在不拥挤的情况下，平衡安排所有必要的视图以及尺寸标注注解的位置。
Decide on a scale that will allow, without crowding, a balanced arrangement of all necessary views and the location of dimensions and notes.
本系统可以很方便查询出用户所要查找的地图上有的位置，并把它按一定比例放大定位在视图中央。
User can expediently look up his demanding position in the system and orient it in center of view.
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