alidad
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al·i·dade
(ăl′ĭ-dād′) also al·i·dad (-dăd′)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 ʕṣ́d in Semitic roots).]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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| Noun | 1. |  alidad - surveying instrument consisting of the upper movable part of a theodolite including the telescope and its attachmentssurveying instrument, surveyor's instrument - an instrument used by surveyors theodolite, transit - a surveying instrument for measuring horizontal and vertical angles, consisting of a small telescope mounted on a tripod |
| 2. |  alidad - surveying instrument used with a plane table for drawing lines of sight on a distant object and for measuring anglessurveying instrument, surveyor's instrument - an instrument used by surveyors |
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