1. An indicator or a sighting apparatus on a plane table, used in angular measurement. 2. A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.
ETYMOLOGY:
French, from Medieval Latin alidada, sighting rod, from Arabic al-‘ida, the revolving radius of a circle : al-, the + ‘ida, revolving radius (alternate form of ‘aud, humerus, from ‘aada, to lop, cut (trees); see cd in Appendix II).
l
-d
d
d in Appendix II).
