gravity variations的用法和樣例：
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.
重力儀的設計是為了測量一處到另一處的重力變化，而不是絕對重力值本身。 - The value of gravimeter surveys for gravity-change detection lies in the fact that gravity change indicates elevation change.
用重力測量檢測重力變化的意義在於，重力變化表示高程變化。
