详细描述：
一般的地图能够自由的缩放，缩放后才开始加载当前”缩放级别“的地图，那么岂不是要提供无穷个缩放级别的地图数据咯？
（因为缩放级别哪怕是[0,1]这个区间也存在无穷个可能）
如
模糊的：
加载后的：
而既然已经能实现，那说明不是这样的，但到底是如何实现的呢？原理是怎么样的？还望好心人能解惑
------解决方案--------------------
that fuzzy pic during the zoom in/out operation is a css trick. There is no data at that particular resolution at all. Most all web gis data are built using pyramid schema, which means the data are only available at certain resolutions (scales).
On each tier of the pyramid, data files are organized as tiles. The deeper the tier is, the more tiles are laid. All these tiles are created beforehand. There is no dynamic rendition.
Here is a good reference from Bing map:
http://msdn.microsoft.com/en-us/library/bb259689.aspx
------解决方案--------------------
不是无穷个，是几个级别，当处在中间级别时，会加载最近的级别的数据，这些图片数据有缩放来匹配比例尺