1. Surveying instrument consisting of the upper movable part of a theodolite including the telescope and its attachments
   "The geologist adjusted the alidad on the theodolite to take precise measurements of the rock formation";
   - alidade
    
2. Surveying instrument used with a plane table for drawing lines of sight on a distant object and for measuring angles
   "The surveyor used an alidad to accurately measure the property boundaries";
   - alidade

Derived forms: alidads

Type of: surveying instrument, surveyor's instrument

Part of: theodolite, transit

Encyclopedia: Alidad, Lorestan