what is an alidade
Related to alidade: telescopic alidade. (Älâ²Ä­-dÄdâ²) also alÂ·iÂ·dad (-dÄdâ²) n. 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.