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[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, alidad
[al-i-dad] /ˈæl ɪˌdæd/ (Show IPA)
Origin of alidade
late Middle English
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 Dictionary, © Random House, Inc. 2015.
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Examples from the web for alidade
  • Most of the actual mapping, however, was done by planetable and telescopic alidade.
  • When carried horizontally while on the tripod, the alidade's weight is an excessive load for the hollow centerpiece to bear.
British Dictionary definitions for alidade


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
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
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