垂すい直ちょく圏けん

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Meanings

1

noun

vertical circle

Astronomical term: a great circle on the celestial sphere passing through the zenith and nadir, perpendicular to the horizon.

droop, suspend, hang

直straightaway, honesty, frankness

圏sphere, circle, radius

子し午ご線せん
子午線 (meridian) is the vertical circle passing through the north and south points of the horizon, while 垂直圏 is any vertical circle.
高こう度ど
高度 (altitude) is the angular distance along a vertical circle from the horizon to a celestial body.

Compound of 垂直 (vertical) and 圏 (circle/sphere), a calque from Western astronomical terminology.