A great circle of the celestial sphere through the zenith and nadir. Vertical circles are perpendicular to the horizon. The prime vertical circle or prime vertical passes through the east and west points of the horizon. The principal vertical circle passes through the north and south points of the horizon and coincides with the celestial meridian.
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SPREAD
The divergence of the air stream in a horizontal or vertical plane after it leaves the outlet.
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GYROSCOPIC DRIFT
The horizontal rotation of the spin axis of a gyroscope about the vertical axis
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HEAVE
The oscillatory vertical rise and fall, due to the entire hull being lifted by the force of the sea. Also called HEAVING
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HEIGHT OF TIDE
Vertical distance from the chart sounding datum to the water surface at any stage of the tide. It is positive if the water level is higher than the chart sounding datum. The vertical distance from the chart sounding datum to a high water datum is called RISE OF TIDE.
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HEELING ERROR INSTRUMENT
Heeling adjuster. Also called VERTICAL FORCE INSTRUMENT
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MODEL ATMOSPHERE
Any theoretical representation of the atmosphere, particularly of vertical temperature distribution.
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WICKING
The vertical absorption of a liquid into a porous material by capillary forces.
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ICE FRONT
The vertical cliff forming the seaward face of an ice shelf or other floating glacier varying in height from 2 to 50 meters above sea level. See also ICE WALL.
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MULTIPLE TIDE STAFF
A succession of tide staffs on a sloping shore so placed that the vertical graduations on the several staffs will form a continuous scale referred to the same datum.
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LUBBER'S LINE
The vertical line inside a compass case indicating the direction of the ship's head.
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