Word Study
Alidade
CIDE DICTIONARY
Alidade, n. [LL. alidada, alhidada, fr. Ar. al-'idāda a sort of rule: cf. F. alidade.].
The portion of a graduated instrument, as a quadrant or astrolabe, carrying the sights or telescope, and showing the degrees cut off on the arc of the instrument Whewell. [1913 Webster]
OXFORD DICTIONARY
Alidade, n. Surveying & Astron. an instrument for determining directions or measuring angles.
Etymology
F f. med.L f. Arab. al-' idada the revolving radius f. ' adud upper arm
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