- a part of an optical or surveying instrument, consisting of the vernier, indicator, etc.
- a surveying instrument consisting of a telescope mounted on a rule, used in topography
Origin of alidadeFrench ; from Spanish alidada ; from Arabic al uncertain or unknown; perhaps i??da, two sides or sideposts ; from uncertain or unknown; perhaps a?ud, upper arm
- An indicator or a sighting apparatus on a plane table, used in angular measurement.
- A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.
Origin of alidadeFrench, from Medieval Latin alidada, sighting rod, from Arabic al-‘i&dlowdot;ada, the revolving radius of a circle : al-, the + ‘i&dlowdot;ada, revolving radius (alternate form of ‘a&dlowdot;ud, humerus, from ‘a&dlowdot;ada, to lop, cut (trees); see &ayin;&saclod;d in Semitic roots).
- (cartography, astronomy, surveying) A sighting device used for measuring angles.