A simple dry magnetic pocket compass

A compass (or mariner compass) is a navigational instrument for finding directions on the Earth. It consists of a magnetized pointer free to align itself accurately with Earth's magnetic field, which is of great assistance in navigation. Earth 's magnetic field (and the surface magnetic field) is approximately a Magnetic dipole, with one pole near the North pole (see Navigation is the process of reading and controlling the movement of a craft or vehicle from one place to another The face of the compass generally highlights the cardinal points of north, south, east and west. The compass greatly improved maritime trade by making travel safer and more efficient. A compass can be used to calculate heading, used with a sextant to calculate latitude, and with a marine chronometer to calculate longitude). In Navigation, a course is the intended path of a vehicle over the surface of the Earth This article is about the sextant as used for Navigation. For the astronomer's sextant, see Sextant (astronomical. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the A marine chronometer is a timekeeper precise enough to be used as a portable Time standard; it can therefore be used to determine Longitude by means of Celestial Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement It thus provides a much improved navigational capability, that has only been recently supplanted by modern devices such as the gyrocompass and the Global Positioning System (GPS). Navigation is the process of reading and controlling the movement of a craft or vehicle from one place to another A gyrocompass is similar to a Gyroscope. It is a Compass that finds True north by using an (electrically powered fast-spinning wheel and friction Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth

An early form of the compass (a magnetized needle floating in water) was invented in China sometime before 1044. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National The familiar dry mariner's compass was invented in Europe around 1300^[1]. This was supplanted in the 20th century by the liquid-filled magnetic compass. Fundamentally, the classic compass is any magnetically sensitive device able to indicate the direction of the magnetic north of a planet's magnetosphere. The Earth's North Magnetic Pole is the wandering point on the Earth's surface at which the Earth's magnetic field points vertically downwards (i A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. Often compasses are built as a stand-alone sealed instrument with a magnetized bar or needle turning freely upon a pivot, or moving in a fluid, thus able to point in a northerly and southerly direction. In the Physical sciences Quality assurance, and Engineering, Measurement is the activity of obtaining and comparing physical quantities This is about the direction for other uses see North (disambiguation. South is one of Cardinal directions and is opposite to the North.

Many enhancements to the compass have been developed. A compass dial is a small pocket compass with a sundial. A sundial is a device that measures time by the position of the Sun. A variation compass is a specific instrument of a delicate type of construction. It is used by observing variations of the needle. An orienteering compass consists of a ruggedized needle compass permanently attached to a transparent baseplate containing tools to assist the user in working with maps in a field setting (as opposed to in an office at a desk). Orienteering is a family of Sports that require Navigational skills using a Map and Compass, usually in combination with Point to point racing A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, Regions, and Themes

Other, more accurate, devices have been invented for determining north that do not depend on the Earth's magnetic field for operation (known in such cases as true north, as opposed to magnetic north). noted by the Chinese Polymath Shen Kuo in the 11th century and possibly the egyptians over 6 millenia ago The magnetic declination (also known as grid magnetic angle in military circles at any point on the Earth is the angle between the local magnetic field -- the direction A gyrocompass or astrocompass can be used to find true north, while being unaffected by stray magnetic fields, nearby electrical power circuits or nearby large masses of ferrous metals. A gyrocompass is similar to a Gyroscope. It is a Compass that finds True north by using an (electrically powered fast-spinning wheel and friction An astrocompass is a navigational tool for determining the direction of North through the positions of various Astronomical bodies A recent development is the electronic compass, which detects the magnetic directions without requiring moving parts. This device frequently appears as an optional subsystem built into GPS receivers.

Construction of a simple compass

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. Lodestone or loadstone refers to either Magnetite, a Magnetic Mineral form of iron(II, Iron(III oxide 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, often by being painted red.

History of the navigational compass

Navigation prior to the compass

Prior to the introduction of the compass, position and direction at sea was primarily determined by the sighting of landmarks, supplemented with the observation of the position of celestial bodies. Ancient mariners usually kept within easy sight of land. The invention of the compass enabled the determination of heading when the sky was overcast or foggy. And, when the sun or other known celestial bodies could be observed, it enabled the calculation of latitude. This enabled mariners to navigate safely away from land, contributing to the Age of Discovery. The Age of Discovery or Age of Exploration was a period from the early 15th century and continuing into the early 17th century during which Europeans explored

Mesoamerica

Based on his find of an Olmec hematite artifact in Central America, the American astronomer John Carlson has suggested that "the Olmec may have discovered and used the geomagnetic lodestone compass earlier than 1000 BC". The Olmec were an ancient Pre-Columbian people living in the Tropical lowlands of south-central Mexico, in what are roughly the modern-day states Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides If true, this "predates the Chinese discovery of the geomagnetic lodestone compass by more than a millennium". ^[2] Carlson speculates that the Olmecs may have used similar artifacts as a directional device for astrological or geomantic purposes, or to orientate their temples, the dwellings of the living or the interments of the dead.

The artifact itself is part of a lodestone that had been polished into a bar with a groove at one end (that Carlson suggests may have been used for sighting). Lodestone or loadstone refers to either Magnetite, a Magnetic Mineral form of iron(II, Iron(III oxide The artifact now consistently points 35. 5 degrees west of north, but may have pointed north-south when whole. It has been suggested that the artifact was in fact used as some constituent piece of a decorative ornament. ^[3] No other similar hematite artifacts have yet been found. Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides

Needle-and-bowl device

By rubbing a needle on another magnet, the needle becomes magnetized and when placed in a cork and put in a bowl of water it becomes a compass. This device was universally used as a compass until the introduction of the box-like compass with a pivoting "dry" needle around 1300.

China

Due to disagreement as to when the compass was invented, it may be appropriate to list some noteworthy Chinese literary references offered as possible evidence for its antiquity, in chronological order:

Reconstruction of a Han Dynasty (206 BC – 220 AD) south-indicating ladle or sinan. Chinese civilization originated in various city-states along the Yellow River ( valley in the Neolithic era The Han Dynasty ( 206 BC–220 AD followed the Qin Dynasty and preceded the Three Kingdoms in China.

• The earliest Chinese literature reference to magnetism lies in a 4th century BC book called Book of the Devil Valley Master (鬼谷子): "The lodestone makes iron come or it attracts it. Chinese literature extends back thousands of years from the earliest recorded dynastic court Archives to the mature fictional Novel that arose during the Ming Dynasty The 4th century BC started the first day of 400 BC and ended the last day of 301 BC. Lodestone or loadstone refers to either Magnetite, a Magnetic Mineral form of iron(II, Iron(III oxide Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 "^[4]
• The first mention of the magnetic attraction of a needle is to be found in a Chinese work composed between 20 and 100 AD (Lun Heng): "A lodestone attracts a needle. Wang Chong ( 27&ndashc 100 AD Wang also accurately described the process of the Water cycle. "^[5] In 1948, the scholar Wang Tchen-touo tentatively constructed a "compass" in the form of south-indicating spoon on the basis of this text. However, it should be noted that "there is no explicit mention of a magnet in the Louen-heng" and that "beforehand it needs to assume some hypotheses to arrive at such a conclusion. "^[6]
• The earliest reference to a specific magnetic direction finder device is recorded in a Song Dynasty book dated to 1040-44. The Song Dynasty ( Wade-Giles: Sung Ch'ao was a ruling dynasty in China between 960&ndash1279 CE it succeeded the Five Dynasties and Ten Kingdoms Here we find a description of an iron "south-pointing fish" floating in a bowl of water, aligning itself to the south. The device is recommended as a means of orientation "in the obscurity of the night. " As Li Shu-hua pointed out in 1954, there was no mention of a use for navigation, nor how the fish was magnetized. ^[7] However, in Needham's publication Science and Civilization in China: Volume 4, Part 1 in 1962, he proved otherwise, as Wang Chenduo had pointed out. The Wujing Zongyao (武经总要, "Collection of the Most Important Military Techniques") of 1044 stated: "When troops encountered gloomy weather or dark nights, and the directions of space could not be distinguished. The Wujing Zongyao ( was a Chinese military compendium written in 1044 AD during the Northern Song Dynasty. . . they made use of the [mechanical] south-pointing carriage, or the south-pointing fish. The South Pointing Chariot is widely regarded as one of the most complex Geared mechanism of the ancient Chinese civilization, and was continually used throughout the "^[8] This was achieved by heating of metal (especially if steel), known today as thermo-remanence, and would have been capable of producing a weak state of magnetization. ^[8]
• The first incontestable reference to a magnetized needle in Chinese literature appears as early as 1088 AD. ^[9] The Dream Pool Essays, written by the Song Dynasty polymath scientist Shen Kuo, contained a detailed description of how geomancers magnetized a needle by rubbing its tip with lodestone, and hung the magnetic needle with one single strain of silk with a bit of wax attached to the center of the needle. The Dream Pool Essays ( Pinyin: Meng Xi Bi Tan; Wade-Giles: Meng Ch'i Pi T'an Chinese: 夢溪筆談／梦溪笔谈 The Song Dynasty ( Wade-Giles: Sung Ch'ao was a ruling dynasty in China between 960&ndash1279 CE it succeeded the Five Dynasties and Ten Kingdoms A polymath ( Greek polymathēs, πολυμαθής "having learned much" is a person whose knowledge is not restricted to one subject area Shen Kuo or Shen Kua ( (1031&ndash1095 style name Cunzhong and pseudonym Mengqi Weng, was a Polymathic Chinese A dial is generally a flat surface circular or rectangular with numbers or similar markings on it used for displaying the setting or output of a Timepiece, Radio Silk is a natural Protein Fiber, some forms of which can be woven into Textiles The best-known type of silk is obtained from cocoons Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their Shen Kuo pointed out that a needle prepared this way sometimes pointed south, sometimes north.
• The earliest recorded actual use of a magnetized needle for navigational purposes then is to be found in Zhu Yu's book Pingzhou Table Talks (萍洲可談; Pingzhou Ketan) of AD 1119 (written from 1111 to 1117 AD): The navigator knows the geography, he watches the stars at night, watches the sun at day; when it is dark and cloudy, he watches the compass. Zhu Yu ( was an author of the Chinese Song Dynasty (960-1279 AD This of course would have been aided by Shen Kuo's discovery (while working as the court's head astronomer) of the concept of true north: magnetic declination towards the magnetic north pole away from the polestar. Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena noted by the Chinese Polymath Shen Kuo in the 11th century and possibly the egyptians over 6 millenia ago The Earth's North Magnetic Pole is the wandering point on the Earth's surface at which the Earth's magnetic field points vertically downwards (i A pole star is a visible star especially a prominent one that is approximately aligned with the Earth 's Axis of rotation; that is a star whose apparent position

Thus, the first clear instance of a magnetic direction finder, a compass, appeared ca. 1044. However, it should be pointed out that the compass remained in use by the Chinese in the form of a magnetic needle floating in a bowl of water. ^[10]

According to Needham, the Chinese in the Song Dynasty and continuing Yuan Dynasty did make use of a dry compass, although this type never became as widely used in China as the wet compass. The Song Dynasty ( Wade-Giles: Sung Ch'ao was a ruling dynasty in China between 960&ndash1279 CE it succeeded the Five Dynasties and Ten Kingdoms The Yuan Dynasty ( Pinyin: Yuáncháo Dai Ön Ulus (Дай Юан Улс was a ruling Dynasty founded by the Mongol leader Kublai ^[11] Evidence of this is found in the Shilinguangji ("Guide Through the Forest of Affairs"), first published in 1325 by Chen Yuanjing, although its compilation had taken place between 1100 and 1250 AD. ^[11] The dry compass in China was a dry suspension compass, a wooden frame crafted in the shape of a turtle hung upside down by a board, with the loadstone sealed in by wax, and if rotated, the needle at the tail would always point in the northern cardinal direction. ^[11] Although the 14th century European compass-card in box frame and dry pivot needle was adopted in China after its use was taken by Japanese pirates in the 16th century (who had in turn learned of it from Europeans),^[12] the Chinese design of the suspended dry compass persisted in use well into the 18th century. The are the dominant Ethnic group of Japan. Worldwide approximately 130 million people are of Japanese descent of these approximately 127 million are residents of Japan ^[13]

However, according to Kreutz there is only a single Chinese reference to a dry-mounted needle (built into a pivoted wooden tortoise) which is dated to between 1150 and 1250, but there is no indication that Chinese mariners ever used anything but the floating needle in a bowl until the 16th-century European contacts. ^[14]

Additionally, it must be pointed out that, unlike Needham, other experts on the history of the compass make no mention of an indigenous dry compass in China and reserve the term for the European form which became later worldwide standard. ^[15][16][17]

Later developments in China

Diagram of a Ming Dynasty mariner's compass

• The first recorded use of a 48 position mariner's compass on sea navigation was noted in a book titled “The Customs of Cambodia” by Yuan dynasty diplomat Zhou Daguan, he described his 1296 voyage from Wenzhou to Angkor Thom in detail; when his ship set sailed from Wenzhou, the mariner took a needle direction of “ding wei” position, which is equivalent to 22. Diplomatic Journey to Cambodia On 20 February 1296, Zhou Daguan set sail from Wenzhou of Zhejiang province on a compass guided ship passed Administration The Prefecture-level city of Wenzhou currently administers 3 district, 2 county-level cities and 6 counties. Angkor Thom ( Khmer: អង្គរធំ was the last and most enduring capital city of the Khmer empire. 5 degree SW. After they arrived at Baria, the mariner took "Kun Shen needle" , or 52. Baria may refer to Baria Bangladesh Baria India 5 degree SW. ^[18]
• Zheng He's Navigation Map, also known as "The Mao Kun Map", contains a large amount of detail "needle records" of Zheng He's travel. Zheng He ( Birth name 馬三寶 / 马三宝; Arabic / Persian name حجّي محمود شمس Hajji Mahmud Shams) (1371&ndash1433 was a Hui ^[19]
• A pilot's compass handbook titled Shun Feng Xiang Song (Fair Winds for Escort) in the Oxford Bodleian Library contains great details about the use of compass in navigation. The Bodleian Library ( the main Research library of the University of Oxford, is one of the oldest libraries in Europe, and in England

Question of diffusion

Navigational sailor's compass rose.

There is much debate on what happened to the compass after its first appearance with the Chinese. Different theories include:

• Travel of the compass from China to the Middle East via the Silk Road, and then to Europe. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East. The Silk Road, or Silk Routes, are an extensive interconnected network of Trade routes across the Asian continent connecting East South and Western Asia with the
• Direct transfer of the compass from China to Europe, and then later from China or Europe to the Middle East. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East.
• Independent creation of the compass in Europe, and thereafter its transfer from China or Europe to the Middle East. The Middle East is a Subcontinent with no clear boundaries often used as a synonym to Near East, in opposition to Far East.

The latter two are supported by evidence of the earlier mentioning of the compass in European works rather than Arabic. The first European mention of a magnetized needle and its use among sailors occurs in Alexander Neckam's De naturis rerum (On the Natures of Things), probably written in Paris in 1190. Alexander ( of) Neckam ( 8 September 1157 &ndash 1217 was an English scholar and teacher Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city ^[20] Other evidence for this includes the Arabic word for "Compass" (al-konbas), possibly being a derivation of the old Italian word for compass. Arabic (ar الْعَرَبيّة (informally ar عَرَبيْ) in terms of the number of speakers is the largest living member of the Semitic language Italian ( or lingua italiana) is a Romance language spoken by about 63 million people as a First language, primarily in Italy.

In the Arab world, the earliest reference comes in The Book of the Merchants' Treasure, written by one Baylak al-Kibjaki in Cairo about 1282. ^[21] Since the author describes having witnessed the use of a compass on a ship trip some forty years earlier, some scholars are inclined to antedate its first appearance accordingly. There is also a slightly earlier non-Mediterranean Muslim reference to an iron fish-like compass in a Persian talebook from 1232. ^[22].

Question of independent European invention

Pivoting compass needle in a 14^th century copy of Epistola de magnete of Peter Peregrinus (1269)

There have been various arguments put forward whether the European compass was an independent invention or not:

Arguments pro independent invention:

• The navigational needle in Europe points invariably north, whereas nearly always south in China. Peter of Maricourt ( Peter Peregrinus of Maricourt; French Pierre de Maricourt; Latin Petrus Peregrinus de Maricourt) (fl
• The European compass showed from the beginning sixteen basic divisions, not twenty-four as in China. ^[23]
• The apparent failure of the Arabs to function as possible intermediaries between East and West due to the earlier recorded appearance of the compass in Europe (1190)^[20] than in the Muslim world (1232, 1242, or 1282). ^{[21] [22]}

Arguments contra independent invention:

• The temporal priority of the Chinese navigational compass (1040-44) as opposed to the European (1190). ^[20]
• The common shape of the early compass as a magnetized needle floating in a bowl of water. ^[24]

Impact in the Mediterranean

In the Mediterranean, the introduction of the mariner's compass, at first only known as a magnetized pointer floating in a bowl of water^[25], went hand in hand with improvements in dead reckoning methods, and the development of Portolan charts, leading to more navigation during winter months in the second half of the 13^th century. Dead reckoning ( DR) is the process of estimating one's current position based upon a previously determined position or fix, and advancing that position based upon A portolan (derived from the Latin word portus, port is an early modern European navigation chart, dating from the Thirteenth century or later ^[26] While the practice from ancient times had been to curtail sea travel between October and April, due in part to the lack of dependable clear skies during the Mediterranean winter, the prolongation of the sailing season resulted in a gradual, but sustained increase in shipping movement: By around 1290 the sailing season could start in late January or February, and end in December. ^[27] The additional few months were of considerable economic importance. For instance, it enabled Venetian convoys to make two round trips a year to the Levant, instead of one. Venice ( Italian: Venezia, Venetian: Venesia or Venexia) is a city in Northern Italy, the capital of the See also Names of the Levant The Levant (lə'vænt is a geographical term that denotes a large area in Western Asia, roughly bounded on the north by the ^[28]

At the same time, traffic between the Mediterranean and northern Europe also increased, with first evidence of direct commercial voyages from the Mediterranean into the English Channel coming in the closing decades of the 13th century, and one factor may be that the compass made traversal of the Bay of Biscay safer and easier. Cantabrian Sea redirects here Not to be confused with Biscay Bay Newfoundland and Labrador or Biscayne Bay. ^[29] Although critics like Kreutz feels that it was later in 1410 that anyone really started steering by compass. ^[30]

Mining

The use of a compass as a direction finder underground was pioneered by the Tuscan mining town Massa where floating magnetic needles were employed for determining tunneling and defining the claims of the various mining companies as early as the 13th century. Massa is a town and comune in Tuscany, Italy, the administrative centre of the Province of Massa-Carrara. ^[31] In the second half of the 15th century, the compass belonged to the standard equipment of Tyrolian miners, and shortly afterwards a first detailed treatise dealing with the underground use of compasses was published by the German miner Rülein von Calw (1463-1525). Tyrol is a region in Western Central Europe, which included the present day Austrian state of Tyrol (consisting of North Tyrol and East Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. ^[32]

Dry compass

The familiar dry compass (commonly called a mariner's compass) was invented in Europe around 1300. The dry mariner's compass consists of three elements: A freely pivoting needle on a pin enclosed in a little box with a glass cover and a wind rose, whereby "the wind rose or compass card is attached to a magnetized needle in such a manner that when placed on a pivot in a box fastened in line with the keel of the ship the card would turn as the ship changed direction, indicating always what course the ship was on". ^[33] While pivoting needles in glass boxes had already been described by the French scholar Peter Peregrinus in 1269,^[34] there is an inclination to honour tradition and credit Flavio Gioja (fl. Peter of Maricourt ( Peter Peregrinus of Maricourt; French Pierre de Maricourt; Latin Petrus Peregrinus de Maricourt) (fl Flavio Gioja or Gioia (fl 1302 was an Italian mariner and inventor 1302), an Italian marine pilot from Amalfi, with perfecting the sailor's compass by suspending its needle over a compass card, giving thus the compass its familiar appearance. A pilot is a Mariner who guides Ships through dangerous or congested waters such as Harbours or River mouths Legally the master remains Amalfi is also a town in the Antioquia Departament in Colombia. ^[35] Such a compass with the needle attached to a rotating card is also described in a commentary on Dante's Divine Comedy from 1380, while an earlier source refers to a portable compass in a box (1318),^[36] supporting the notion that the dry compass was known in Europe by then. The Divine Comedy ^[37]

Bearing compass

Bearing compass (18th century).

A bearing compass is a magnetic compass mounted in such a way that it allows the taking of bearings of objects by aligning them with the lubber line of the bearing compass. In Navigation, a bearing is the direction one object is from another object ^[38] A surveyor's compass is a specialized compasses made to accurately measure heading of landmarks and measure horizontal angles to help with map making. A circumferentor, or surveyor's compass, is an instrument used in Surveying to measure horizontal angles now superseded by the Theodolite. These were already in common use by the early 18th century and are described in the 1728 Cyclopaedia. Cyclopaedia or A Universal Dictionary of Arts and Sciences ( folio, 2 vols Later, a prism and lens was mounted on top of a compass in such a way that enabled the user to accurately sight the heading of geographical landmarks, thus creating the prismatic compass. The Bezard compass was invented in 1906, and consists of a compass with a mirror mounted above it. ^[39] This enabled the user to easily see the face of the compass while also walking and viewing the surrounding landscape.

Modern compasses

Liquid filled lensatic compass

Modern compasses usually use a magnetized needle or dial inside a fluid-filled capsule (oil, kerosene, or alcohol is common). The fluid dampens the movement of the needle and causes the needle to stabilize quickly rather than oscillate back and forth around magnetic north. North on the needle or dial is usually marked with phosphorescent paint, to enable the compass to be read at night or poor light. Luminous (or luminescent) paint exhibits Luminescence. In other words it gives off visible Light through Fluorescence, Phosphorescence

Many modern hand held recreational and military compasses integrate a protractor with the compass, using a separate magnetized needle. A sighting compass or hand compass is a navigational device used to determine direction on the Earth while allowing for sighting a target and viewing your bearing In Geometry, a protractor is a circular or semicircular tool for measuring an Angle or a Circle. In this design the rotating capsule containing the magnetized needle is fitted with orienting lines and an outlined orienting arrow, then mounted in a transparent baseplate containing a direction-of-travel (DOT) indicator for use in taking bearings directly from a map.

Other features found on some modern compasses are map and romer scales for measuring distances and plotting positions on maps, luminous markings on the face or bezels, various sighting mechanisms (mirror, prism, etc. ) for taking bearings of distant objects with greater precision, "global" needles for use in differing hemispheres, adjustable declination for obtaining instant true bearings without resort to arithmetic, and devices such as inclinometers for measuring gradients.

The military forces of a few nations, notably the United States Army, continue to utilize older lensatic card compass designs with magnetized compass dials instead of needles. A lensatic card compass permits reading the bearing off of the compass card with only a slight downward glance from the sights (see photo), but requires a separate protractor for use with a map. The official U. S. military lensatic compass does not use fluid to dampen needle swing, but rather electromagnetic induction to dampen the needle. Faraday's law of induction describes an important basic law of electromagnetism which is involved in the working of Transformers Inductors and many forms of A "deep-well" design is used to allow the compass to be used globally with little or no effect in accuracy caused by a tilting compass dial. 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. The use of air-filled induction compasses has declined over the years, as they may become inoperative or inaccurate in freezing temperatures or humid environments.

Mariner's compasses can have two or more magnetic needles permanently attached to a compass card. These move freely on a pivot. 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. Traditionally the card is divided into thirty-two points (known as rhumbs), although modern compasses are marked in degrees rather than cardinal points. The glass-covered box (or bowl) contains a suspended gimbal within a binnacle. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many A gimbal is a pivoted support that allows the rotation of an object about a single axis A binnacle is a case or box on the deck of a Ship, generally mounted in front of the Helmsman,in which navigational instruments are placed for easy and This preserves the horizontal position.

Some modern military compasses, like the SandY-183, contains the radioactive material tritium (3H) and a combination of phosphors. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. The SandY-183 contained 120mCi (millicuries) of tritium. The purpose of the tritium and phosphors is to provide illumination for the compass. This illumination is a form of fluorescence, not requiring the compass to be "recharged" by sunlight or artificial light. Self-powered lighting is a generic term describing devices that emit light continuously without an external power source The name SandY-183 is derived from the name of the company, Stocker and Yale (SandY)^[40].

Points of the compass

Main article: Boxing the compass

Originally, many compasses were marked only as to the direction of magnetic north, or to the four cardinal points (north, south, east, west). Later, mariners divided the compass card into thirty-two equally spaced points divided from the cardinal points. For a table of the thirty-two points, see compass points.

The 360-degree system later took hold, which is still in use today for civilian navigators. The degree dial spaces the compass markings with 360 equidistant points. Other nations adopted the "grad" system, which spaces the dial into 400 grads or points.

Most military defense forces have adopted the "mil" system, in which the compass dial is spaced into 6400 units (some nations use 6000) or "mils" for additional precision when measuring angles, laying artillery, etc. The value to the military is that one mil subtends approximately one metre at a distance of one kilometer.

Former Warsaw Pact countries (Soviet Union, GDR etc. The Warsaw Pact (see Nomenclature) was an organization of Communist states in Central and Eastern Europe. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 The German Democratic Republic ( GDR; Deutsche Demokratische Republik DDR; commonly known in English as East Germany) was a Socialist state ) used a 60° graduation, often counterclockwise (see picture of wrist compass). This is still in use in Russia.

Gyrocompass

Main article: Gyrocompass

A gyrocompass is similar to a gyroscope. A gyrocompass is similar to a Gyroscope. It is a Compass that finds True north by using an (electrically powered fast-spinning wheel and friction It is a 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. noted by the Chinese Polymath Shen Kuo in the 11th century and possibly the egyptians over 6 millenia ago Gyrocompasses are widely used on ships. A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size 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 ferrous metal in a ship's hull. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The Earth's North Magnetic Pole is the wandering point on the Earth's surface at which the Earth's magnetic field points vertically downwards (i (No compass is affected by nonferrous metal, although a magnetic compass will be affected by non-ferrous wires with current running through them. )

Large ships typically rely on a gyrocompass, using the magnetic compass only as a backup. A gyrocompass is similar to a Gyroscope. It is a Compass that finds True north by using an (electrically powered fast-spinning wheel and friction Increasingly, electronic fluxgate compasses are used on smaller vessels. The basic fluxgate compass is a simple Electromagnetic device that employs two or more small coils of wire around a core of highly permeable magnetic material to directly sense However compasses are still widely in use as they can be small, use simple reliable technology, are comparatively cheap, often easier to use than GPS, require no energy supply, and unlike GPS, are not affected by objects, e. Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth g, trees that can block the reception of electronic signals.

Solid state compasses

Small compasses found in clocks, cell phones, e. g. , the Nokia 5140i, and other electronic gear are solid-state devices, usually built out of two or three magnetic field sensors that provide data for a microprocessor. Solid-state Electronic components devices and systems are based entirely on the Semiconductor, such as Transistors Microprocessor chips and Using trigonometry the correct heading relative to the compass is calculated. Circle-trig6svg|300px|thumb|right|All of the Trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O.

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 used either internally, or sent to a display unit. A microcontroller (also MCU or µC is a functional Computer system-on-a- chip. A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated An example implementation, including parts list and circuit schematics, shows one design of such electronics. The sensor uses precision magnetics and highly calibrated internal electronics to measure the response of the device to the Earth's magnetic field. The electrical signal is then processed or digitized. Digital electronics are Electronics systems that use Digital signals Digital electronics are representations of Boolean algebra also see

Specialty compasses

A range of specialty compasses would include a Qibla compass, which is used by Muslims to show the direction to Mecca for prayers. A qibla compass or qiblih compass (sometimes also called qibla/qiblih indicator) is a modified Compass designed to indicate the direction of prayer Similarly, a Jerusalem compass ^[41] is used by Jews to point the direction of Jerusalem for prayers.

Other specialty compasses include the optical or prismatic hand-bearing compass, often used by surveyors, cave explorers, or mariners. This compass uses an oil-filled capsule and magnetized compass dial with an integral optical or prismatic sight, often fitted with built-in photoluminescent or battery-powered illumination. Using the optical or prism 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 solid metal housings, and many are fitted for tripod mounting for additional accuracy.

Using a compass

Turning the compass scale on the map (D - the local magnetic declination)

When the needle is aligned with and superimposed over the outlined orienting arrow on the bottom of the capsule, the degree figure on the compass ring at the direction-of-travel (DOT) indicator gives the magnetic bearing to the target (mountain).

The simplest way of using a compass is to know that the arrow always points in the same direction, magnetic North, which is roughly similar to true north. Except in areas of extreme magnetic declination variance (20 degrees or more), this is enough to protect from walking in a substantially different or even opposite direction than expected over short distances, provided the terrain is fairly flat and visibility is not impaired. In fact, 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.

However, compass navigation used in conjunction with a map (terrain association) requires a different compass method. To take a map bearing or true bearing (a bearing taken in reference to true, not magnetic north) to a destination with a protractor compass, the edge of the compass is placed on the map so that it connects the current location with the desired destination (some sources recommend physically drawing a line). The protractor compass is a type of Compass commonly often used in Hill walking, Orienteering and other outdoor sports and pursuits 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. The resulting true bearing or map bearing may then be read at the degree indicator or direction-of-travel (DOT) line, which may be followed as an azimuth (course) to the destination. If a magnetic north bearing or compass bearing is desired, the compass must be adjusted by the amount of magnetic declination before using the bearing so that both map and compass are in agreement. In the given example, the large mountain in the second photo was selected as the target destination on the map.

The modern hand-held protractor compass always has an additional direction-of-travel (DOT) arrow or indicator inscribed on the baseplate. The protractor compass is a type of Compass commonly often used in Hill walking, Orienteering and other outdoor sports and pursuits To check one's progress along a course or azimuth, or to ensure that the object in view is indeed the destination, a new compass reading may be taken to the target if visible (here, the large mountain). 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. The resulting bearing indicated is the magnetic bearing to the target. Again, if one is using "true" or map bearings, and the compass does not have preset, pre-adjusted declination, one must additionally add or subtract magnetic declination to convert the magnetic bearing into a true bearing. The magnetic declination (also known as grid magnetic angle in military circles at any point on the Earth is the angle between the local magnetic field -- the direction The exact value of the magnetic declination is place-dependent and varies over time, though declination is frequently given on the map itself or obtainable on-line from various sites. If not, any local walker club should know it. If the hiker has been following the correct path, the compass' corrected (true) indicated bearing should closely correspond to the true bearing previously obtained from the map.

Compass correction

Main article: Magnetic deviation

A binnacle containing a ship's steering compass, with the two iron balls which correct the effects of ferromagnetic materials

Like any magnetic device, compasses are affected by nearby ferrous materials as well as by strong local electromagnetic forces. Magnetic deviation is the error induced in a Compass by local Magnetic fields which must be allowed for along with Magnetic declination, if A binnacle is a case or box on the deck of a Ship, generally mounted in front of the Helmsman,in which navigational instruments are placed for easy and Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it Compasses used for wilderness land navigation should never be used in close proximity to ferrous metal objects or electromagnetic fields (batteries, car bonnets, engines, steel pitons, wristwatches, etc. )

Compasses used in or near trucks, cars or other mechanized vehicles are particularly difficult to use accurately, 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. Magnetic deviation is the error induced in a Compass by local Magnetic fields which must be allowed for along with Magnetic declination, if Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 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. A lubber line is a fixed-line displayed on a Compass Binnacle or Radar Plan position indicator display pointing towards the front of the ship 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. Ferromagnetism is the basic mechanism by which certain materials (such as Iron) form Permanent magnets and/or exhibit strong interactions with Magnets it The coefficient a₀ representing the error in the lubber line, while a₁,b₁ the ferromagnetic effects and a₂,b₂ the non-ferromagnetic component.

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 compasses can be calibrated automatically, and can also be programmed with the correct local compass variation so as to indicate the true heading.

Compass balancing

Because the Earth's magnetic field's inclination and intensity vary at different latitudes, compasses are often balanced during manufacture. 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. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' For a topic outline on this subject see List of basic Australia topics. This balancing prevents excessive dipping of one end of the needle which can cause the compass card to stick and give false readings.

See also

Gallery

Compass with 400 grads division and conversion table	Swiss army compass with mils divisions	Compass with prism (inverted graduation)	Compass with prism (bearing 220° through eyepiece)	Land surveyor compass with clinometer
Wrist compass of the Soviet Army with dual graduations — 60° (like a watch) and 360° (below the figures for 15°, 30° and 45° of the outer graduation are the Cyrillic letters "З" (zapad = west), "Ю"(yug = south) and "В" (vostok = east)	Stratum compass after Prof. Azimuth ( is a mathematical concept defined as the angle usually measured in degrees (° between a reference plane and a point. A Brunton compass, properly known as the Brunton Pocket Transit, is a type of precision Compass made by Brunton Cammenga is an outdoors products company most known for their high-grade Compasses and weapon applications For Compass Airlines an Airline in the US using the Callsign "Compass Rose" See Compass Airlines A compass rose is a figure displaying the orientation In Mathematics and its applications a coordinate system is a system for assigning an n - Tuple of Numbers or scalars to each point The Earth inductor compass is a device for determining direction using the Magnetic field of the Earth. The basic fluxgate compass is a simple Electromagnetic device that employs two or more small coils of wire around a core of highly permeable magnetic material to directly sense Basic concept of GPS operation A GPS receiver calculates its position by carefully timing the signals sent by the constellation of GPS Satellites high above the Earth A gyrocompass is similar to a Gyroscope. It is a Compass that finds True north by using an (electrically powered fast-spinning wheel and friction A sighting compass or hand compass is a navigational device used to determine direction on the Earth while allowing for sighting a target and viewing your bearing An Inertial Navigation System (INS is a Navigation aid that uses a Computer and motion sensors to continuously track the position orientation and Velocity Marching lines are a pair of lines drawn on the glass of a Compass, and arranged at 45 degrees to each other In appearance and use a pelorus resembles a Compass or Compass repeater, with sighting vanes or a sighting telescope attached but it has no directive properties The protractor compass is a type of Compass commonly often used in Hill walking, Orienteering and other outdoor sports and pursuits A radio direction finder ( RDF) is a device for finding the direction to a Radio source A radio direction finder ( RDF) is a device for finding the direction to a Radio source A circumferentor, or surveyor's compass, is an instrument used in Surveying to measure horizontal angles now superseded by the Theodolite. A Thumb compass is a type of Compass commonly used in Orienteering, a sport in which map reading and terrain association are paramount A Thumb compass is a type of Compass commonly used in Orienteering, a sport in which map reading and terrain association are paramount Ze (З з is a letter of the Cyrillic alphabet, representing the consonant /z/ Yu (Ю ю is a letter of the Cyrillic alphabet, representing either the combination /ju/ (a so-called iotated vowel or /u/ after a palatalized consonant Ve (В в is the third letter of the Cyrillic alphabet, representing the sound /v/ Clar	German Bézard compass (Company Lufft) formerly utilized in many European armies (bearing is taken through slots in lid)	A simple compass typical to a small yacht	A compass suitable for orienteering at night
World War I German aircraft compass from the collection of the Museum of Australian Army Flying.

Notes

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. Amir D Aczel (born November 6, 1950) is a lecturer in mathematics and the history of mathematics and science and an author of popular books on mathematics and science , New York : Harcourt, ISBN 0-15-600753-3
• Carlson, John B. (1975) "Lodestone Compass: Chinese or Olmec Primacy?: Multidisciplinary analysis of an Olmec hematite artifact from San Lorenzo, Veracruz, Mexico”, Science, 189 (4205 : 5 September), p. 753-760, DOI 10. 1126/science. 189. 4205. 753
• 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
• Gurney, Alan (2004) Compass: A Story of Exploration and Innovation, London : Norton, ISBN 0-393-32713-2
• Kreutz, Barbara M. Frances Gies (born 1915 and Joseph Gies (1916-2006 are historians and writers who have collaborated on a number of books about the Middle Ages, and have also written (1973) "Mediterranean Contributions to the Medieval Mariner's Compass", Technology and Culture, 14 (3: July), p. 367–383
• Lane, Frederic C. (1963) "The Economic Meaning of the Invention of the Compass", The American Historical Review, 68 (3: April), p. 605–617
• Li Shu-hua (1954) "Origine de la Boussole 11. Aimant et Boussole", Isis, 45 (2: July), p. 175–196
• Ludwig, Karl-Heinz and Schmidtchen, Volker (1997) Metalle und Macht: 1000 bis 1600, Propyläen Technikgeschichte, Berlin : Propyläen-Verl. , ISBN 3-549-05633-8
• Ma, Huan (1997) Ying-yai sheng-lan [The overall survey of the ocean's shores (1433)], Feng, Ch'eng-chün (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
• Taylor, E. G. R. (1951) "The South-Pointing Needle", Imago Mundi, 8, p. 1–7
• Williams, J. E. D. (1992) From Sails to Satellites: the origin and development of navigational science, Oxford University Press, ISBN 0-19-856387-6
• 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

External links

• USGS Geomagnetism Program
• Science Friday, "The Riddle of the Compass" (interview with Amir Aczel, first broadcast on NPR on May 31, 2002). Events 1279 BC - Rameses II (The Great (19th dynasty becomes pharaoh of Ancient Egypt. See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar.
• Paul J. Gans, The Medieval Technology Pages: Compass
• The Tides By Sir William Thomson (Lord Kelvin)
• Evening Lecture To The British Association At The Southampton Meeting on Friday, August 25, 1882 [1]. William Thomson 1st Baron Kelvin (or Lord Kelvin) OM, GCVO, PC, PRS, FRSE, (26 June 1824 &ndash 17 December 1907 Refers to compass correction by Fourier series. In Mathematics, a Fourier series decomposes a periodic function into a sum of simple oscillating functions
• Arrick Robots. Robotics. com Example implementation for digital solid-state compass. ARobot Digital Compass App Note
• How a tilt sensor works. David Pheifer [2]
• The Gear Junkie - review of two orienteering thumb compasses
• The good compass video - A video about important abilities a compass should have
• BEWARE : The Brief History of the Bezard compass (1852 – 1971) on the Knowfuture site is a hoax. There is no such village in France. A Jewish family Bézard never existed. The Bezard compass was created by Johann von Bézard, an Austrian Colonel of French Huguenot origin and built by the LUFFT company in Germany whose factory was in Stuttgart. Stuttgart (ˈʃtʊtgaɐ̯t is the capital of the state of Baden-Württemberg in southern Germany. The BASF chemical company is situated on the river Rhine in Ludwigshafen. The Rhine (Rhein Rijn Rhin Reno Rain Rhenus is one of the longest and most important Rivers in Europe at 1320 kilometres (820 mi with an average discharge Ludwigshafen am Rhein is a City in Rhineland-Palatinate, Germany. The whole story is beautiful but unfortunately untrue. Reliable information can be found on the following private sites:
  • Der Bézard-Kompaß (German)
  • La Original Bezard... (Italian).
• Compass collector : rare old compasses (Bézard)!
• The virtual compass museum - the greatest collection of compasses
• Geography fieldwork
• Travel Island