The traditional geometrical leveling is inconvenient in fluctuating area.
在地形起伏较大地区，几何水准测量十分不便。
The traditional methods are geometrical leveling and trigonometric leveling. They have different advantage and disadvantage.
传统的测量方法为水准测量和三角高程测量，它们都存在着不同的优缺点。
The key of GPS leveling across sea is that the height datum on each side of channel is not consistent, so the general geometrical fitting method can not be used directly.
GPS跨海水准的关键问题是海峡两侧的高程基准不一致，因此无法采用常规的数值拟合方法。
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