alidade

[al-i-deyd]

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)

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for alidade

Historical Examples of alidade

Close by stood an alidade, an instrument for measuring angles.
Historical Miniatures
August Strindberg
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
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

alidade

alidad (ˈælɪˌdæd)

noun

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