俯ふ角かく

noun

depression angle; angle of dip

Technical term in geometry, surveying, and optics for the angle below the horizontal plane when looking downward.

• 測そく量りょうでは、俯ふ角かくを正せい確かくに測そく定ていすることが重じゅう要ようだ。

  In surveying, it is important to measure the depression angle accurately.

• この望ぼう遠えん鏡きょうの俯ふ角かくは最さい大だいで30度どまで調ちょう整せいできる。

  The depression angle of this telescope can be adjusted up to 30 degrees.