Answer: alidads

AnswerCrossword Clue
ALIDADSSurveyors' telescopes: Var.
alidadsthe entire upper part of a theodolite or transit, including the telescope, its supports, the level vials, the circle-reading device, and the spindle
alidads(in plane-tabling) a straightedge having a telescopic sight or other means of sighting parallel to the straightedge
alidadsALIDAD, a device used in angular measurement, also ALIDADE