The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. It is a non-magnetic compass that finds true north by using an (electrically powered) fast-spinning wheel and friction forces in order to exploit the rotation of the Earth. Copyright © 12/11/2020 Alamy Ltd. All rights reserved. (U.S. Air Force photo/Airman Jenna K. Caldwell),, Binnacle compass for steering a course, located in front of the wheel on the main deck of of the sailing ship the Cutty Sark. An instrument for determining directions upon the earth's surface by means of a magnetized bar or needle turning freely upon a pivot and pointing in a northerly and southerly direction.

The adjustable legs with pointed tips provide sure footing on virtually any surface. 4. Please add to your ad blocking whitelist or disable your adblocking software. We do not implement these annoying types of ads! Mariners have long known that these measures do not completely cancel deviation; hence, they performed an additional step by measuring the compass bearing of a landmark with a known magnetic bearing. A gyrocompass is a type of non-magnetic compass which is based on a fast-spinning disc and the rotation of the Earth (or another planetary body if used elsewhere in the universe) to find geographical direction automatically. Fluxgate electronic compasses can be calibrated automatically, and can also be programmed with the correct local compass variation so as to indicate the true heading. These numbers allow the compass to show magnetic North azimuths or true North azimuths or bearings, which are commonly stated in this notation. This sliding counterweight, called a 'rider', can be used for counterbalancing the needle against the dip caused by inclination if the compass is taken to a zone with a higher or lower dip.[30]. Among the Four Great Inventions, the magnetic compass was first invented as a device for divination as early as the Chinese Han Dynasty (since c. 206 BC), and later adopted for navigation by the Song Dynasty Chinese during the 11th century. Depending on where the compass is located on the surface of the Earth the angle between true north and magnetic north, called magnetic declination can vary widely with geographic location. Wane/Mao 5 W00 ntoz 'PB 'YIJ EMIL KLAHN, OF MORRIS PLAINS, NEW J NON-MAGNETIC COMPASS. A lubber line, which can be a marking on the compass bowl or a small fixed needle, indicates the ship's heading on the compass card. Consequently, the illumination of the display will fade. After pointing the DOT arrow on the baseplate at the target, the compass is oriented so that the needle is superimposed over the orienting arrow in the capsule.

Compass navigation in conjunction with a map (terrain association) requires a different method. The orienting lines in the base of the compass dial are then rotated to align with actual or true north by aligning them with a marked line of longitude (or the vertical margin of the map), ignoring the compass needle entirely. [23] As induction forces provide less damping than fluid-filled designs, a needle lock is fitted to the compass to reduce wear, operated by the folding action of the rear sight/lens holder. Local environments may contain magnetic mineral deposits and artificial sources such as MRIs, large iron or steel bodies, electrical engines or strong permanent magnets. 766,921.

Sighting. The use of a gyrocompass is one of the seven fundamental ways to determine the heading of a vehicle.

GPS compasses share the main advantages of gyrocompasses. The locations of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation. Specification of Letters Patent. To see if the needle is well leveled, look closely at the needle, and tilt it slightly to see if the needle is swaying side to side freely and the needle is not contacting the casing of the compass. (105),, Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . "within the compass of an encircling wall". [34] Deviation refers to the response of the compass to local magnetic fields caused by the presence of iron and electric currents; one can partly compensate for these by careful location of the compass and the placement of compensating magnets under the compass itself.

In a gyroscope: a suitable frame; a second frame supported thereby and rotatable about a vertical axis; a spinning member mounted in said second frame; an inverted 1 cup-shaped member movable with said second frame; and open at the bottom to the atmosphere and means extending from said first named frame and opening lnto the in-. a The compass can be corrected in three ways. Greenwich, London.

A thumb compass is a type of compass commonly used in orienteering, a sport in which map reading and terrain association are paramount. North corresponds to 0°, and the angles increase clockwise, so east is 90° degrees, south is 180°, and west is 270°. For example, a magnetised rod can be created by repeatedly rubbing an iron rod with a magnetic lodestone. When a thick ironplate is used it forms a perfect shield to the needle againstthe action of the bar magnet.

For other uses, see. North corresponds to 0°, and the angles increase clockwise, so east is 90° degrees, south is 180°, and west is 270°. A rotatably mounted .gyroscope and means to provide a suitable bearing therefor; means to su port said gyroscope independently of said bearing, and means to v supply airunder pressure thereto with a free escape therefrom to eliminate substantially the frictional resistance to taming about its vertical axis and without disturbing the gyrosco e. 3. an area in which something acts or operates or has power or control: "in the political orbit of a world power", drafting instrument used for drawing circles, "This writer attempts more than his talents can compass", "Do you comprehend the meaning of this letter?". The triangle ACF, being cut by thetransversal DB, gives DC X FB,, JOINT BASE MCGUIRE-DIX-LAKEHURST, N.J. – Spc. Two sensors that utilize two of the remaining six principles are often also called compasses, i.e. RENEWED OCT. 22, 19:7. Compasses of the type automatically identify directions by themselves without requiring additional adjustments from humans. Key points on the compass, including the north end of the needle are often marked with phosphorescent, photoluminescent, or self-luminous materials[16] to enable the compass to be read at night or in poor light. A magnetic or electronic device used to determine the cardinal directions (usually magnetic or true north). By carefully recording distances (time or paces) and magnetic bearings traveled, one can plot a course and return to one's starting point using the compass alone.[35].

the direction in which its nose is pointing. These directions may be different if there is a crosswind or tidal current. Manufactured completely of non-magnetic aluminum and brass with a standard 1/4" #20 thread, this deluxe professional tripod is ready for any situation. Compasses used for wilderness land navigation should not be used in proximity to ferrous metal objects or electromagnetic fields (car electrical systems, automobile engines, steel pitons, etc.) The value to the military is that one angular mil subtends approximately one metre at a distance of one kilometer.