Definition of "alidade" []

• An indicator or a sighting apparatus on a plane table, used in angular measurement. (noun)
• A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The alidade is a triangular ruler with one or more working scales on it beside other measurements."
• "Surveyors would place an alidade on the plane table and sight along it to a particular object, then draw a line to indicate the bearing."
• "The mariner sighted the objects along a rule called an alidade."