- 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 ?i??da, two sides or sideposts from ?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;āda the revolving radius of a circle al- the 'i&dlowdot;āda revolving radius ( alternate form of 'a&dlowdot;ud humerus ) ( from 'a&dlowdot;ada to lop, cut (trees) &ayin;&saclod;d)
- (cartography, astronomy, surveying) A sighting device used for measuring angles.