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{{About|the direction finding instrument used in navigation}}{{pp|small=yes}}(File:Kompas Sofia.JPG|thumb|A simple dry magnetic portable compass)File:Smartphone Compass.jpg|thumb|upright|A smartphone that can be used as a compass because of the magnetometermagnetometerA compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal directions (or points). Usually, a diagram called a compass rose shows the directions north, south, east, and west on the compass face as abbreviated initials. When the compass is used, the rose can be aligned with the corresponding geographic directions; for example, the "N" mark on the rose points northward. Compasses often display markings for angles in degrees in addition to (or sometimes instead of) the rose. North corresponds to 0Â°, and the angles increase clockwise, so east is 90Â° degrees, south is 180Â°, and west is 270Â°. These numbers allow the compass to show magnetic North azimuths or true North azimuths or bearings, which are commonly stated in this notation. If magnetic declination between the magnetic North and true North at latitude angle and longitude angle is known, then direction of magnetic North also gives direction of true North.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),Li Shu-hua, p. 176 and later adopted for navigation by the Song Dynasty Chinese during the 11th century.Kreutz, p. 367Needham, p. 252Li Shu-hua, p. 182f. The first usage of a compass recorded in Western Europe and the Islamic world occurred around 1190.Kreutz, p. 370ENCYCLOPEDIA, Oxford University Press, 978-0-19-981257-8, Ibrahim Kalin, Schmidl, Petra G., Compass, The Oxford Encyclopedia of Philosophy, Science, and Technology in Islam, 2014-05-08, 144â€“146,

## {{anchor|The magnetic compass}}Magnetic compass

File:Military Compass of J. Lindsay Brough.jpg|thumb|upright|A military compass that was used during World War IWorld War IThe magnetic compass is the most familiar compass type. It functions as a pointer to "magnetic north", the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the Earth's magnetic field. The magnetic field exerts a torque on the needle, pulling the North end or pole of the needle approximately toward the Earth's North magnetic pole, and pulling the other toward the Earth's South magnetic pole.The magnetic lines of force in the Earth's field do not accurately follow great circles around the planet, passing exactly over the magnetic poles. Therefore the needle of a compass only approximately points to the magnetic poles. The needle is mounted on a low-friction pivot point, in better compasses a jewel bearing, so it can turn easily. When the compass is held level, the needle turns until, after a few seconds to allow oscillations to die out, it settles into its equilibrium orientation.In navigation, directions on maps are usually expressed with reference to geographical or true north, the direction toward the Geographical North Pole, the rotation axis of the Earth. 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. The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. The locations of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation. The effect of this means a map with the latest declination information should be used.WEB,weblink Declination Adjustment on a Compass, Rei.com, 2015-06-06, Some magnetic compasses include means to manually compensate for the magnetic declination, so that the compass shows true directions.

## Non-magnetic compasses

There are other ways to find north than the use of magnetism, and from a navigational point of view a total of seven possible ways exist (where magnetism is one of the seven). Two sensors that utilize two of the remaining six principles are often also called compasses, i.e. the gyrocompass and GPS-compass.

### Gyrocompass

A gyrocompass is similar to a gyroscope. 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. Gyrocompasses are widely used on ships. They have two main advantages over magnetic compasses:
• they find true north, i.e., the direction of Earth's rotational axis, as opposed to magnetic north,
• they are not affected by ferromagnetic metal (including iron, steel, cobalt, nickel, and various alloys) in a ship's hull. (No compass is affected by nonferromagnetic metal, although a magnetic compass will be affected by any kind of wires with electric current passing through them.)
Large ships typically rely on a gyrocompass, using the magnetic compass only as a backup. Increasingly, electronic fluxgate compasses are used on smaller vessels. However, magnetic compasses are still widely in use as they can be small, use simple reliable technology, are comparatively cheap, are often easier to use than GPS, require no energy supply, and unlike GPS, are not affected by objects, e.g. trees, that can block the reception of electronic signals.

### GPS receivers used as compasses

GPS receivers using two or more antennae mounted separately and blending the data with an inertial motion unit (IMU) can now achieve 0.02Â° in heading accuracy and have startup times in seconds rather than hours for gyrocompass systems. The devices accurately determine the positions (latitudes, longitudes and altitude) of the antennae on the Earth, from which the cardinal directions can be calculated. Manufactured primarily for maritime and aviation applications, they can also detect pitch and roll of ships. Small, portable GPS receivers with only a single antenna can also determine directions if they are being moved, even if only at walking pace. By accurately determining its position on the Earth at times a few seconds apart, the device can calculate its speed and the true bearing (relative to true north) of its direction of motion. Frequently, it is preferable to measure the direction in which a vehicle is actually moving, rather than its heading, i.e. the direction in which its nose is pointing. These directions may be different if there is a crosswind or tidal current.GPS compasses share the main advantages of gyrocompasses. They determine true North,JOURNAL, Gade, Kenneth, 2016, The Seven Ways to Find Heading, The Journal of Navigation, 69, 5, 955â€“970,weblink PDF, 10.1017/S0373463316000096, as opposed to magnetic North, and they are unaffected by perturbations of the Earth's magnetic field. Additionally, compared with gyrocompasses, they are much cheaper, they work better in polar regions, they are less prone to be affected by mechanical vibration, and they can be initialized far more quickly. However, they depend on the functioning of, and communication with, the GPS satellites, which might be disrupted by an electronic attack or by the effects of a severe solar storm. Gyrocompasses remain in use for military purposes (especially in submarines, where magnetic and GPS compasses are useless), but have been largely superseded by GPS compasses, with magnetic backups, in civilian contexts.

## History

The first compasses in ancient Han dynasty China were made of lodestone, a naturally magnetized ore of iron.BOOK, Lowrie, William, Fundamentals of Geophysics, 2007, Cambridge University Press, London, 978-0-521-67596-3, 281, Early in the Han Dynasty, between 300â€“200 BC, the Chinese fashioned a rudimentary compass out of lodestone ... the compass may have been used in the search for gems and the selection of sites for houses ... their directive power led to the use of compasses for navigation, JOURNAL, Guarnieri, M., 2014, Once Upon a Time, the Compass, IEEE Industrial Electronics Magazine, 8, 2, 60â€“63, 10.1109/MIE.2014.2316044, harv, The compass was later used for navigation during the Song Dynasty of the 11th century.BOOK, Merrill, Ronald T., The Earth's magnetic field: Its history, origin and planetary perspective, 1983, Academic press, San Francisco, 978-0-12-491242-7, 1, 2nd printing, McElhinny, Michael W., Later compasses were made of iron needles, magnetized by striking them with a lodestone. Dry compasses began to appear around 1300 in Medieval Europe and the Islamic world.Lane, p. 615 This was supplanted in the early 20th century by the liquid-filled magnetic compass.W.H. Creak: "The History of the Liquid Compass", The Geographical Journal, Vol. 56, No. 3 (1920), pp. 238â€“239

## Modern compasses

(File:walkers compass arp.jpg|thumb|upright|A liquid-filled protractor or orienteering compass with lanyard)

### Magnetic compass

#### Thumb compass

(File:Compasses orienteering.jpg|thumb|Thumb compass on left)A thumb compass is a type of compass commonly used in orienteering, a sport in which map reading and terrain association are paramount. Consequently, most thumb compasses have minimal or no degree markings at all, and are normally used only to orient the map to magnetic north. An oversized rectangular needle or north indicator aids visibility. Thumb compasses are also often transparent so that an orienteer can hold a map in the hand with the compass and see the map through the compass. The best models use rare-earth magnets to reduce needle settling time to 1 second or less.

### Solid state compasses

File:Motorola Xoom - AKM Semiconductor AKM8975-1693.jpg|thumb|3-axis electronic magnetometer AKM8975 by AKM Semiconductor ]]Small compasses found in clocks, mobile phones, and other electronic devices are solid-state microelectromechanical systems (MEMS) compasses, usually built out of two or three magnetic field sensors that provide data for a microprocessor. Often, the device is a discrete component which outputs either a digital or analog signal proportional to its orientation. This signal is interpreted by a controller or microprocessor and either used internally, or sent to a display unit. The sensor uses highly calibrated internal electronics to measure the response of the device to the Earth's magnetic field.

### Specialty compasses

(File:Brunton.JPG|thumb|A standard Brunton Geo, used commonly by geologists)Apart from navigational compasses, other specialty compasses have also been designed to accommodate specific uses. These include:
• Qibla compass, which is used by Muslims to show the direction to Mecca for prayers.
• Optical or prismatic hand-bearing compass, most often used by surveyors, but also by cave explorers, foresters, and geologists. These compasses generally use a liquid-damped capsuleKramer, Melvin G., U.S. Patent No. 4175333, Magnetic Compass, Riverton, Wyoming: The Brunton Company, pub. 27 November 1979: The Brunton Pocket Transit, which uses magnetic induction damping, is an exception. and magnetized floating compass dial with an integral optical sight, often fitted with built-in photoluminescent or battery-powered illumination.BOOK, Johnson, G. Mark, 2003-03-26, The Ultimate Desert Handbook, McGraw-Hill Professional, 978-0-07-139303-4, 113â€“114, Using the optical sight, such compasses can be read with extreme accuracy when taking bearings to an object, often to fractions of a degree. Most of these compasses are designed for heavy-duty use, with high-quality needles and jeweled bearings, and many are fitted for tripod mounting for additional accuracy.
• Trough compasses, mounted in a rectangular box whose length was often several times its width, date back several centuries. They were used for land surveying, particularly with plane tables.

### Limitations of the magnetic compass

(File:×ž×¦×¤×Ÿ.jpg|alt=A close up photo of a geological compass|thumb|A close up photo of a geological compass)The magnetic compass is very reliable at moderate latitudes, but in geographic regions near the Earth's magnetic poles it becomes unusable. As the compass is moved closer to one of the magnetic poles, the magnetic declination, the difference between the direction to geographical north and magnetic north, becomes greater and greater. At some point close to the magnetic pole the compass will not indicate any particular direction but will begin to drift. Also, the needle starts to point up or down when getting closer to the poles, because of the so-called magnetic inclination. Cheap compasses with bad bearings may get stuck because of this and therefore indicate a wrong direction.Magnetic compasses are influenced by any fields other than Earth's. Local environments may contain magnetic mineral deposits and artificial sources such as MRIs, large iron or steel bodies, electrical engines or strong permanent magnets. Any electrically conductive body produces its own magnetic field when it is carrying an electric current. Magnetic compasses are prone to errors in the neighborhood of such bodies. Some compasses include magnets which can be adjusted to compensate for external magnetic fields, making the compass more reliable and accurate.A compass is also subject to errors when the compass is accelerated or decelerated in an airplane or automobile. Depending on which of the Earth's hemispheres the compass is located and if the force is acceleration or deceleration the compass will increase or decrease the indicated heading. Compasses that include compensating magnets are especially prone to these errors, since accelerations tilt the needle, bringing it closer or further from the magnets.Another error of the mechanical compass is turning error. When one turns from a heading of east or west the compass will lag behind the turn or lead ahead of the turn. Magnetometers, and substitutes such as gyrocompasses, are more stable in such situations.

## Construction of a magnetic compass

### Magnetic needle

A magnetic rod is required when constructing a compass. This can be created by aligning an iron or steel rod with Earth's magnetic field and then tempering or striking it. However, this method produces only a weak magnet so other methods are preferred. For example, a magnetised rod can be created by repeatedly rubbing an iron rod with a magnetic lodestone. This magnetised rod (or magnetic needle) is then placed on a low friction surface to allow it to freely pivot to align itself with the magnetic field. It is then labeled so the user can distinguish the north-pointing from the south-pointing end; in modern convention the north end is typically marked in some way.

### Needle-and-bowl device

If a needle is rubbed on a lodestone or other magnet, the needle becomes magnetized. When it is inserted in a cork or piece of wood, and placed in a bowl of water it becomes a compass. Such devices were universally used as compass until the invention of the box-like compass with a 'dry' pivoting needle sometime around 1300.

### Compass balancing (magnetic dip)

Because the Earth's magnetic field's inclination and intensity vary at different latitudes, compasses are often balanced during manufacture so that the dial or needle will be level, eliminating needle drag which can give inaccurate readings. Most manufacturers balance their compass needles for one of five zones, ranging from zone 1, covering most of the Northern Hemisphere, to zone 5 covering Australia and the southern oceans. This individual zone balancing prevents excessive dipping of one end of the needle which can cause the compass card to stick and give false readings.Global compasses, MapWorld.Some compasses feature a special needle balancing system that will accurately indicate magnetic north regardless of the particular magnetic zone. Other magnetic compasses have a small sliding counterweight installed on the needle itself. 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.

### Compass correction

File:MuseeMarine-compas-p1000468.jpg|thumb|upright|A binnacle containing a ship's standard compass, with the two iron balls which correct the effects of ferromagnetic materials. This unit is on display in a museum.]]Like any magnetic device, compasses are affected by nearby ferrous materials, as well as by strong local electromagnetic forces. 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.) as that can affect their accuracy.BOOK, Johnson, G. Mark, 2003-03-26, The Ultimate Desert Handbook, McGraw-Hill Professional, 978-0-07-139303-4, 122, Compasses are particularly difficult to use accurately in or near trucks, cars or other mechanized vehicles even when corrected for deviation by the use of built-in magnets or other devices. Large amounts of ferrous metal combined with the on-and-off electrical fields caused by the vehicle's ignition and charging systems generally result in significant compass errors.At sea, a ship's compass must also be corrected for errors, called deviation, caused by iron and steel in its structure and equipment. The ship is swung, that is rotated about a fixed point while its heading is noted by alignment with fixed points on the shore. A compass deviation card is prepared so that the navigator can convert between compass and magnetic headings. The compass can be corrected in three ways. First the lubber line can be adjusted so that it is aligned with the direction in which the ship travels, then the effects of permanent magnets can be corrected for by small magnets fitted within the case of the compass. The effect of ferromagnetic materials in the compass's environment can be corrected by two iron balls mounted on either side of the compass binnacle in concert with permanent magnets and a Flinders bar.WEB,weblink Handbook of Magnetic Compass Adjustment, GEOSPATIAL-INTELLIGENCE AGENCY, National, 2004, The coefficient a_0 represents the error in the lubber line, while a_1,b_1 the ferromagnetic effects and a_2,b_2 the non-ferromagnetic component.JOURNAL
, Lushnikov
, E.
,
, Magnetic Compass in Modern Maritime Navigation
, TransNav, the International Journal on Marine Navigation and Safety of Sea Transportation
, 9
, 4
, 539â€“543
, December 2015
,
,
, 2083-6481
, 10.12716/1001.09.04.10
,
,
,
,
, 11 February 2016,
A similar process is used to calibrate the compass in light general aviation aircraft, with the compass deviation card often mounted permanently just above or below the magnetic compass on the instrument panel. 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.

## Using a magnetic compass

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{{reflist}}

## References

• Admiralty, Great Britain (1915) Admiralty manual of navigation, 1914, Chapter XXV: "The Magnetic Compass (continued): the analysis and correction of the deviation", London : HMSO, 525 p.
• Aczel, Amir D. (2001) The Riddle of the Compass: The Invention that Changed the World, 1st Ed., New York : Harcourt, {{ISBN|0-15-600753-3}}
• JOURNAL, Carlson, John B, 1975, Multidisciplinary analysis of an Olmec hematite artifact from San Lorenzo, Veracruz, Mexico, Science, 189, 4205, 753â€“760, 10.1126/science.189.4205.753, 17777565, 1975Sci...189..753C,
• Gies, Frances and Gies, Joseph (1994) Cathedral, Forge, and Waterwheel: Technology and Invention in the Middle Age, New York : HarperCollins, {{ISBN|0-06-016590-1}}
• Gubbins, David, Encyclopedia of Geomagnetism and Paleomagnetism, Springer Press (2007), {{ISBN|1-4020-3992-1|978-1-4020-3992-8}}
• Gurney, Alan (2004) Compass: A Story of Exploration and Innovation, London : Norton, {{ISBN|0-393-32713-2}}
• Johnson, G. Mark, The Ultimate Desert Handbook, 1st Ed., Camden, Maine: McGraw-Hill (2003), {{ISBN|0-07-139303-X}}
• JOURNAL, King, David A., 1983, The Astronomy of the Mamluks, Isis (journal), Isis, 74, 4, 531â€“555, 10.1086/353360, harv,
• Kreutz, Barbara M. (1973) "Mediterranean Contributions to the Medieval Mariner's Compass", Technology and Culture, 14 (3: July), pp. 367â€“383 {{JSTOR|3102323}}
• Lane, Frederic C. (1963) "The Economic Meaning of the Invention of the Compass", The American Historical Review, 68 (3: April), pp. 605â€“617 {{JSTOR|1847032}}
• Li Shu-hua (1954) "Origine de la Boussole 11. Aimant et Boussole", Isis, 45 (2: July), pp. 175â€“196
• Ludwig, Karl-Heinz and Schmidtchen, Volker (1997) Metalle und Macht: 1000 bis 1600, PropylÃ¤en Technikgeschichte, Berlin: PropylÃ¤en Verlag, {{ISBN|3-549-05633-8}}
• Ma, Huan (1997) Ying-yai sheng-lan [The overall survey of the ocean's shores (1433)], Feng, Ch'eng-chÃ¼n (ed.) and Mills, J.V.G. (transl.), Bangkok : White Lotus Press, {{ISBN|974-8496-78-3}}
• Needham, Joseph (1986) Science and civilisation in China, Vol. 4: "Physics and physical technology", Pt. 1: "Physics", Taipei: Caves Books, originally publ. by Cambridge University Press (1962), {{ISBN|0-521-05802-3}}
• Needham, Joseph and Ronan, Colin A. (1986) The shorter Science and civilisation in China : an abridgement of Joseph Needham's original text, Vol. 3, Chapter 1: "Magnetism and Electricity", Cambridge University Press, {{ISBN|0-521-25272-5}}
• Seidman, David, and Cleveland, Paul, The Essential Wilderness Navigator, Ragged Mountain Press (2001), {{ISBN|0-07-136110-3}}
• JOURNAL, Taylor, E.G.R., 1951, The South-Pointing Needle, Imago Mundi, 8, 1â€“7, 10.1080/03085695108591973,
• Williams, J.E.D. (1992) From Sails to Satellites: the origin and development of navigational science, Oxford University Press, {{ISBN|0-19-856387-6}}
• Wright, Monte Duane (1972) Most Probable Position: A History of Aerial Navigation to 1941, The University Press of Kansas, {{LCCN|72079318}}
• Zhou, Daguan (2007) The customs of Cambodia, translated into English from the French version by Paul Pelliot of Zhou's Chinese original by J. Gilman d'Arcy Paul, Phnom Penh : Indochina Books, prev publ. by Bangkok : Siam Society (1993), {{ISBN|974-8298-25-6}}

{{Commons and category|Compass|Compasses}}
{{Flight instruments}}{{Aircraft components}}{{Orienteering|type=collapsed}}{{Sensors}}{{Authority control}}

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