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).]
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.alidad - surveying instrument consisting of the upper movable part of a theodolite including the telescope and its attachmentsalidad - surveying instrument consisting of the upper movable part of a theodolite including the telescope and its attachments
surveying 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 anglesalidad - surveying instrument used with a plane table for drawing lines of sight on a distant object and for measuring angles
surveying instrument, surveyor's instrument - an instrument used by surveyors