Crossword clues for alidade
alidade
The Collaborative International Dictionary
Alidade \Al"i*dade\, n. [LL. alidada, alhidada, fr. Ar.
al-'id[=a]da a sort of rule: cf. F. alidade.]
The portion of a graduated instrument, as a quadrant or
astrolabe, carrying the sights or telescope, and showing the
degrees cut off on the arc of the instrument
--Whewell.
Wiktionary
n. (context cartography astronomy surveying English) A sighting device used for measuring angles.
WordNet
Wikipedia
An alidade (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. This task can be, for example, to draw a line on a plane table in the direction of the object or to measure the angle to the object from some reference point. Angles measured can be horizontal, vertical or in any chosen plane.
The alidade was originally a part of many types of scientific and astronomical instrument. At one time, some alidades, particularly those used on graduated circles as on astrolabes, were also called diopters. With modern technology, the name is applied to complete instruments such as the plane table alidade.
Usage examples of "alidade".
Hugh sat outside with the astrolabe in his hands, turning it over, spinning the alidade, tracing the lines on the plates with his fingers, and obviously having no idea how to use it even to tell time.
Hugh sat outside with the astrolabe in his hands, turning it over, spinning the alidade,tracing the lines on the plates with his fingers, and obviously having no idea how to use it even to tell time.
The alidade, or diametral rule, which served as a sun sight, could pick up the sun's shadow, and throw it across the coinciding circles of time and latitude.
The surveyors of the time did not have alidades, mountain transits, nor pocket transits like the Brunton compass.
With the help of the alidades, a watch with known slip, and an ephemeris, the students would be able to locate themselves.