gravity variations的用法和样例：
例句
- Gravity instruments are designed to measure variation in the force of gravity from one place to another rather than the absolute force itself.
重力仪的设计是为了测量一处到另一处的重力变化，而不是绝对重力值本身。 - The value of gravimeter surveys for gravity-change detection lies in the fact that gravity change indicates elevation change.
用重力测量检测重力变化的意义在于，重力变化表示高程变化。
