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alidad

 - 2 dictionary results

al⋅i⋅dade

  [al-i-deyd]
Use alidad in a Sentence
–noun Surveying.
1. (in plane-tabling) a straightedge having a telescopic sight or other means of sighting parallel to the straightedge.
2. 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] .

Origin:
1400–50; var. of alhidade < ML alhidada < Ar al-ʿiḍādah the turning radius (like a clock hand) of a circle; r. late ME allydatha (< OSp alhidada)
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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al·i·dade   (āl'ĭ-dād')   
n.  

  1. An indicator or a sighting apparatus on a plane table, used in angular measurement.

  2. A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.


[French, from Medieval Latin alidada, sighting rod, from Arabic al-'iḍāda, the revolving radius of a circle : al-, the + 'iḍāda, revolving radius (alternate form of 'aḍud, humerus, from 'aḍada, to lop, cut (trees); see ʕd in Semitic roots).]
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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