| an imaginary line running along the earth's surface from the North to the South Pole, lying everywhere exactly in a north-south direction |
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| an imaginary line obtained by slicing the earth's surface with a plane parallel to equatorial plane |
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| the angular distance on the earth east or west of a meridian from the standard meridian which passes through Greenwich |
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| the point in the heavens vertically above a person on the earth |
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