alidade

[ al-i-deyd ]

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.

alidade

/ ˈælɪˌdeɪd; ˈælɪˌdæd /

noun

1. a surveying instrument used in plane-tabling for drawing lines of sight on a distant object and taking angular measurements
2. the upper rotatable part of a theodolite, including the telescope and its attachments

Word History and Origins

Origin of alidade¹

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 )

Word History and Origins

Origin of alidade¹

C15: from French, from Medieval Latin allidada, from Arabic al-'idāda the revolving radius of a circle

Example Sentences

Field artillery required a precision instrument known as the miniature telescopic alidade of the Gale type.

From Project Gutenberg

A very simple alidade may be made by mounting two needles on a ruler.

From Project Gutenberg

Close by stood an alidade, an instrument for measuring angles.

From Project Gutenberg

After he had placed the plane table on a tripod and upon this the alidade, he started to work.

From Project Gutenberg

The alidade is a triangular ruler with one or more working scales on it beside other measurements.

From Project Gutenberg