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1 In mathematics, an instrument for making circles and measuring distances. Frequently called a pair of compasses, it consists of two metal legs with one end of each attached to a pivot to form a V-shaped device. The free ends are pointed; a pen or pencil may be substituted for one of the points. 2 In navigation, an instrument for determining direction. The mariner's compass consists of a magnetic needle freely suspended so that in the earth's magnetic field it turns until aligned with the magnetic north and south poles. Declination is the angle between the magnetic needle and the geographical meridian. Use of the compass by the early Chinese is probably legendary. The first known reference in European literature dates from the 12th cent. Another more accurate form of navigational compass is the gyrocompass. It consists essentially of a rapidly spinning, electrically driven rotor, suspended in such a way that its axis automatically points along the geographical meridian. The gyrocompass is unaffected by magnetic influences. This compass came into wide use in warships and aircraft during the Second World War. See gyroscopegyroscope
, symmetrical mass, usually a wheel, mounted so that it can spin about an axis in any direction. When spinning, the gyroscope has special properties. Many spinning objects exhibit some of these properties; the rotation of the earth about its axis gives it the
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a direction-finding instrument. According to principle of operation, a distinction is made among magnetic compasses, which use the property of straight permanent magnets (magnetic pointers) or coils with electric current of assuming a north-south orientation along a magnetic meridian upon interaction with the earth’s magnetic field; gyrocompasses, which use the property of a rapidly spinning gyroscope rotor of maintaining a constant direction of its axis of rotation, which, under certain conditions, remains in the plane of a geographic meridian; celestial compasses, in which a special device (a direction finder) continuously tracks the location of some celestial body (for example, the sun), making possible determination of the direction of the geographic meridian if the geographic coordinates of the location are known; and radio compasses, which are radio receiving devices that automatically lock in the direction toward a radio beacon. Compasses are used in maritime and aircraft navigation (to determine the course of a vessel or aircraft and to find the direction toward a reference point), in overland travel, in military affairs, and in geodesy, topography, and mining.

The oldest and most widely known type of compass is the magnetic type. Permanent magnets were used in China more than 2,000 years ago to determine the north-south direction. In Europe the compass appeared not later than the 12th century; it consisted of a magnetic pointer attached to a cork floating in a water-filled vessel. During the early part of the 14th century the compass was improved: the magnetic pointer was placed on a point located in the center of a paper circle (a compass rose), which was graduated for convenient reading. The circle was subdivided first into 16 and later 32 equal sectors.

In the 16th century a gimbal suspension was introduced to reduce mechanical vibrations (for example, during rolling and pitching at sea). In the 17th century marine compasses were equipped with a direction finder—a rotating rule with sights at both ends—which facilitated accurate reading of directions or bearings. The improved magnetic compass became the main navigational instrument for determining the course of a ship. The reading accuracy of currently used ship’s magnetic compasses in medium latitudes and in the absence of pitch and roll can attain 0.3°˗0.5°.

An aircraft magnetic compass has the same basic parts as a ship’s compass, but the aircraft design takes into account some operational conditions peculiar to this type of service, such as possible strong vibrations and accelerations.

Among the disadvantages of a magnetic compass are the need to introduce reading corrections to compensate for the noncoincidence of the magnetic and geographic meridians (consideration of magnetic declination) and for deviation. Near the earth’s magnetic poles and strong magnetic anomalies the accuracy of the readings of a magnetic compass is drastically reduced; in such localities other types of compasses must be used. However, none of the types mentioned above can provide an accurate course reading in all areas of the earth, under any weather conditions, and for any state of the magnetosphere and radio interference level. For this reason it is customary in marine and air travel and military affairs to use a combination of several types of compasses; consolidated course-finding systems are based on such combined use.


Anderson, E. Printsipy navigatsii. Moscow, 1968. (Translated from English.)
Seleznev, V. P. Navigatsionnye ustroistva. Moscow, 1961.



(in Russian, krontsirkul’ ), a drawing instrument for constructing circles 2–80 mm in diameter. There are drawing compasses with a screw joint between the measuring legs, as well as compasses that have a vertically mounted support leg and a movable measuring leg, whose position is fixed by a screw (the balerinka, or “little ballerina”).



(in Russian, tsirkul’), an instrument used to draw circles or arcs, to measure the lengths of line segments, to transfer dimensions, or to scale measured dimensions up or down.

The following main types of compasses are distinguished: dividers, drawing compasses, bow compasses, beam compasses, and proportional compasses (see Figure 1). Dividers, which do not have a pen or pencil point, are used to measure or transfer linear dimensions. Drawing compasses are employed to draw circles with diameters of up to 300 mm; bow compasses, circles with diameters of 2 to 80 mm; and beam compasses, circles with diameters of more than 300 mm. Proportional compasses make it possible to change the scale of measured dimensions.

Figure 1. Compasses: (a) divider, (b) bow compass, (c) proportional compass, (d) drawing compass, (e) drop compass (the balerinka, or “little ballerina”), (f) beam compass

Based on the evidence of drawn circles that have been preserved, the ancient Babylonians and Assyrians used compasses. In France, an iron compass was discovered in a Gallic barrow dating from the first century of the Common Era. Many bronze compasses used by the Romans during the first century of the Common Era were found in the ruins of Pompeii; they represent all the modern types of compasses. In addition to simple compasses, the Roman instruments include proportional compasses for enlarging or reducing the scale of measured dimensions and calipers for measuring the inside and outside diameters of objects.

In ancient Rus’, a compass-drawn ornament consisting of tiny perfect circles was widely used on articles made of bone. A compasslike steel cutter for scribing the ornament was found during archaeological excavations in Novgorod.

What does it mean when you dream about a compass?

Guidance. Finding one’s way out of situation in which one feels lost. We also talk about our “moral compass,” which guides us in making ethical choices.


An instrument for indicating a horizontal reference direction relative to the earth.
(graphic arts)
An instrument used for describing arcs or circles with pencil or pen; has two legs hinged together at the top.


An instrument for drawing circles, measuring the distance between two points, etc.; consists of two pointed legs, movable on a joint or pivot, usually made so that one of the points can be detached for the insertion of a pen, extension, etc.


1. an instrument used for drawing circles, measuring distances, etc., that consists of two arms, joined at one end, one arm of which serves as a pivot or stationary reference point, while the other is extended or describes a circle
2. Music the interval between the lowest and highest note attainable by a voice or musical instrument


COMPrehensive ASSembler.

The assembly language on CDC computers.
References in classic literature ?
You readily discern the advantages of this invention," he was saying to Thuvan Dihn, who had accompanied him to the landing-stage upon the palace roof to inspect the compass and bid his young friend farewell.
A dozen officers of the court with several body servants were grouped behind the jeddak and his guest, eager listeners to the conversation--so eager on the part of one of the servants that he was twice rebuked by a noble for his forwardness in pushing himself ahead of his betters to view the intricate mechanism of the wonderful "controlling destination compass," as the thing was called.
See here," and he indicated a device at the right of the destination compass.
I asked Juag then what our course was, for he had had the compass last.
The compass, since he had learned its uses from me, had been all that he had to buoy his hope of eventual salvation from the watery deep.
There sat Benson as wide awake as could be, and the compass showed that we were heading straight into the west.
Either the sun was rising in the south, or the compass had been tampered with.
He shouted Borckman to come aft and haul in the whaleboat, while he hurried below for his electric torch and a boat compass.
As he steered, he kept flashing the torch on the boat compass so that he could keep headed north-east by east a quarter east.
This child, with his innocent outlook upon life, was the compass that showed them the point to which they had departed from what they knew, but did not want to know.
Nor was the madness of it so great as to the compass, for if it was ten miles about, I was like to have time enough to do it in; but I did not consider that my goats would be as wild in so much compass as if they had had the whole island, and I should have so much room to chase them in that I should never catch them.
the hedge-rows, and the trees; the pretty cottages, the beds of flowers, the old churchyards, the antique houses, and every well-known object; the exquisite delights of that one journey, crowding in the short compass of a summer's day, the joy of many years, with the winding up with Home and all that makes it dear; no tongue can tell, or pen of mine describe.