Reference ground, sometimes called a return path or signal common, is usually the reference potential of interest.

参考地，通常是指潜在的参考端，有时被称为回路或公用信号。

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The Instrument Rating gives the ability to control the aircraft without reference to the ground or horizon, using flight and navigation instruments.

仪表等级赋予飞行员控制飞机的能力，而不用参考地面或地平线，只使用飞行和导航仪表。

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The truss structure that needs to be riveted, if the height of the ground running from the ground can not meet the riveting operation, it can be used as a horizontal reference.

需要进行铆接的桁架结构，如果大车运行轨道地面离地面的高度不能满足铆接作业时，可以另搭一个一定高度的架子作为水平基准。

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The Civil Aviation Authority said helicopters in London have only limited radar help and fly mostly using visual reference points on the ground.

CNN: London helicopter crash prompts safety questions

Rodriguez's reference to standing his ground is similar to the claim made by George Zimmerman, a neighborhood watch volunteer who is citing Florida's Stand Your Ground law in his defense in the fatal February shooting of an unarmed teenager, Trayvon Martin.

MSN: Texas man gets 40 years in Stand Your Ground case