Subtense Instrument

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Subtense Instrument

 

an instrument used for the measurement and construction of angles. A subtense instrument is used in artillery when firing data are fully prepared by graphical methods and in topographic surveying with the aid of a telestereoscope. The instrument relates an angle to a chord on a circle with a given radius and is used instead of chord tables. The chord scale on a subtense instrument is not uniform. The accuracy of measurement with a subtense instrument is one graduation of the deflection scale, that is, 1/1,000 of the radius of the circle. Angles may be constructed or measured with greater accuracy by using a subtense instrument and a divider than by using a protractor or a celluloid protractor.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.