[ al-i-deyd ]
/ ˈæl ɪˌdeɪd /

noun Surveying.

(in plane-tabling) a straightedge having a telescopic sight or other means of sighting parallel to the straightedge.
the entire upper part of a theodolite or transit, including the telescope, its supports, the level vials, the circle-reading device, and the spindle.
Also al·i·dad [al-i-dad] /ˈæl ɪˌdæd/.

Origin of alidade

1400–50; variant of alhidade < Medieval Latin alhidada < Arabic al-ʿiḍādah the turning radius (like a clock hand) of a circle; replacing late Middle English allydatha (< Old Spanish alhidada) Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for alidade

  • Your scale is ready to be pasted or transferred to the alidade and each 6.8.

    Military Instructors Manual|James P. Cole and Oliver Schoonmaker
  • The alidade is a triangular ruler with one or more working scales on it beside other measurements.

    Military Instructors Manual|James P. Cole and Oliver Schoonmaker
  • Close by stood an alidade, an instrument for measuring angles.

    Historical Miniatures|August Strindberg
  • After he had placed the plane table on a tripod and upon this the alidade, he started to work.

    On the Seaboard|August Strindberg

British Dictionary definitions for alidade


alidad (ˈælɪˌdæd)

/ (ˈælɪˌdeɪd) /


a surveying instrument used in plane-tabling for drawing lines of sight on a distant object and taking angular measurements
the upper rotatable part of a theodolite, including the telescope and its attachments

Word Origin for alidade

C15: from French, from Medieval Latin allidada, from Arabic al-'idāda the revolving radius of a circle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012