Globalization

From Wikipedia, the free encyclopedia

Eastern Telegraph Company 1899 chart of underseatelegraph cabling. An example of modern globalizingtechnology in the beginning of the 20th century.

Globalization is the process of international integration arising from the interchange of world views, products, ideas, and other aspects of culture.^[1][2] Globalization describes the interplay across cultures of macro-social forces. These forces include religion, politics, and economics. Globalization can erode and universalize the characteristics of a local group.^[3] Advances intransportation and telecommunications infrastructure, including the rise of the Internet, are major factors in globalization, generating further interdependence of economic and cultural activities.^[4]

Though several scholars place the origins of globalization in modern times, others trace its history long before the European age of discovery and voyages to the New World. Some even trace the origins to the third millennium BCE.^[5][6] Since the beginning of the 20th century, the pace of globalization has proceeded at an exponential rate.^[7]

In 2000, the International Monetary Fund (IMF) identified four basic aspects of globalization: trade and transactions, capital and investment movements, migration and movement of people and the dissemination of knowledge.^[8] Further, environmental challenges such as climate change, cross-boundary water and air pollution, and over-fishing of the ocean are linked with globalization.^[9] Globalizing processes affect and are affected by business and work organization, economics, socio-cultural resources, and the natural environmen

MIGRATION

Human Migration Guide (6-8)
You may reproduce this handout for students.
© 2005 National Geographic Society. All rights reserved.
What is Human Migration?
Migration (human) is the movement of people from one place in the
world to another for the purpose of taking up permanent or
semipermanent residence, usually across a political boundary. An example
of "semipermanent residence" would be the seasonal movements of
migrant farm laborers. People can either choose to move ("voluntary
migration") or be forced to move ("involuntary migration").
Migrations have occurred throughout human history, beginning with the movements of the
first human groups from their origins in East Africa to their current location in the world.
Migration occurs at a variety of scales: intercontinental (between continents),
intracontinental (between countries on a given continent), and interregional (within
countries).  One of the most significant migration patterns has been rural to urban
migration—the movement of people from the countryside to cities in search of opportunities.
Types of Migration
Internal Migration: Moving to a new home within a state, country, or continent.
External Migration: Moving to a new home in a different state, country, or continent.
Emigration: Leaving one country to move to another (e.g., the Pilgrims emigrated from
England).
Immigration: Moving into a new country (e.g., the Pilgrims immigrated to America).
Population Transfer: When a government forces a large group of people out of a region,
usually based on ethnicity or religion. This is also known as an involuntary or forced
migration.
Impelled Migration (also called "reluctant" or "imposed" migration): Individuals are
not forced out of their country, but leave because of unfavorable situations such as warfare,
political problems, or religious persecution.
Step Migration: A series of shorter, less extreme migrations from a person's place of origin
to final destination—such as moving from a farm, to a village, to a town, and finally to a city.
Chain Migration:  A series of migrations within a family or defined group of people. A chain
migration often begins with one family member who sends money to bring other family
members to the new location. Chain migration results in migration fields—the clustering of
people from a specific region into certain neighborhoods or small towns. Human Migration Guide (6-8) Page 2 of 5
www.nationalgeographic.com/xpeditions © 2005 National Geographic Society. All rights reserved.
Return Migration: The voluntary movements of immigrants back to their place of origin.
This is also known as circular migration.
Seasonal Migration: The process of moving for a period of time in response to labor or
climate conditions (e.g., farm workers following crop harvests or working in cities off-season;
"snowbirds" moving to the southern and southwestern United States during winter).
People Who Migrate
Emigrant: A person who is leaving a country to reside in another.
Immigrant: A person who is entering a country from another to take up new residence.
Refugee: A person who is residing outside the country of his or her origin due to fear of
persecution for reasons of race, religion, nationality, membership in a particular social group,
or political opinion.
Internally Displaced Person (IDP): A person who is forced to leave his or her home region
because of unfavorable conditions (political, social, environmental, etc.) but does not cross
any boundaries.
Migration Stream: A group migration from a particular country, region, or city to a certain
destination.
Why Do People Migrate?
People move for a variety of reasons. They consider the advantages and disadvantages of
staying versus moving, as well as factors such as distance, travel costs, travel time, modes of
transportation, terrain, and cultural barriers.
Push Factors: Reasons for emigrating (leaving a place) because of a difficulty (such as a
food shortage, war, flood, etc.).
Pull Factors: Reasons for immigrating (moving into a place) because of something desirable
(such as a nicer climate, better food supply, freedom, etc.).
Several types of push and pull factors may influence people in their movements (sometimes
at the same time), including:
1. Environmental  (e.g., climate, natural disasters)
2. Political (e.g., war)
3. Economic (e.g., work)
4. Cultural (e.g., religious freedom, education)Human Migration Guide (6-8) Page 3 of 5
www.nationalgeographic.com/xpeditions © 2005 National Geographic Society. All rights reserved.
Place Utility: The desirability of a place based on its social, economic, or environmental
situation, often used to compare the value of living in different locations. An individual’s idea
of place utility may or may not reflect the actual conditions of that location.
Intervening Opportunities: Opportunities nearby are usually considered more attractive
than equal or slightly better opportunities farther away, so migrants tend to settle in a
location closer to their point of origin if other factors are equal.
Distance Decay: As distance from a given location increases, understanding of that location
decreases. People are more likely to settle in a (closer) place about which they have more
knowledge than in a (farther) place about which they know and understand little.
Laws of Migration
Geographer E.G. Ravenstein developed a series of migration 'laws' in the 1880s that form the
basis for modern migration theory. In simple language, these principles state:
• Most migrants travel only a short distance.
• Migrants traveling long distances usually settle in urban areas.
• Most migration occurs in steps.
• Most migration is rural to urban.
• Each migration flow produces a movement in the opposite direction ("counterflow").
• Most migrants are adults.
• Most international migrants are young males, while more internal migrants are female.
Impacts of Migration
Human migration affects population patterns and characteristics, social and cultural patterns
and processes, economies, and physical environments.  As people move, their cultural traits
and ideas diffuse along with them, creating and modifying cultural landscapes.
Diffusion: The process through which certain characteristics (e.g., cultural traits, ideas,
disease) spread over space and through time.
Relocation Diffusion: Ideas, cultural traits, etc. that move with people from one place to
another and do not remain in the point of origin.
Expansion Diffusion: Ideas, cultural traits, etc., that move with people from one place to
another but are not lost at the point of origin, such as language.  
Cultural markers: Structures or artifacts (e.g., buildings, spiritual places, architectural
styles, signs, etc.) that reflect the cultures and histories of those who constructed or occupy
them.  Human Migration Guide (6-8) Page 4 of 5
www.nationalgeographic.com/xpeditions © 2005 National Geographic Society. All rights reserved.
Measuring Migration
In-migration: people moving into one place from another place within a nation (internal
migration).
Out-migration: people moving out of one place to another place within a nation (internal
migration).
Gross migration: total number of in-migrants and out-migrants (internal migration).
Net internal migration: the difference between in-migration and out-migration.
Movers from abroad: people coming into a nation from another country or part of the
world.
Net migration: the difference between net internal migration and movers from abroad.
Migrations Resources
U.S. Census Bureau
http://www.census.gov/
Population Reference Bureau
http://www.prb.org/Content/NavigationMenu/PRB/Educators/Human_Population/Migration2/M
igration1.htm
CSISS Classics: Ernest George Ravenstein—The Laws of Migration, 1885
http://www.csiss.org/classics/content/90
Ancestry.com: Thirteen Reasons Our Ancestors Migrated
http://www.ancestry.com/learn/library/article.aspx?article=1436
AngliaCampus: Migration
http://www.angliacampus.com/public/sec/geog/migrate/index.htm
RevisionNotes.Co.UK: Migration
http://www.revision-notes.co.uk/revision/171.html
Smithsonian Institution: Migrations in History
http://smithsonianeducation.org/migrations/start.html
Migration Information Source
http://www.migrationinformation.org/
UNHCR: The UN Refugee Agency
http://www.unhcr.ch/cgi-bin/texis/vtx/homeHuman Migration Guide (6-8) Page 5 of 5
www.nationalgeographic.com/xpeditions © 2005 National Geographic Society. All rights reserved.
International Organization for Migration
http://www.iom.int/
Migration Dialogue
http://migration.ucdavis.edu/index.php
Netherlands Interdisciplinary Demographic Institute (NIDI)/EuroStat: Push and Pull Factors of
International Migration
http://www.nidi.knaw.nl/web/html/pushpull/index.html
National Geographic Magazine: Changing America
http://www7.nationalgeographic.com/ngm/data/2001/09/01/html/ft_20010901.3.html
National Geographic: Xpeditions—Geography Standard 9 - The Characteristics, Distribution,
and Migration of Human Population on Earth’s Surface
http://www.nationalgeographic.com/xpeditions/standards/09/index.html
National Geographic: Xpeditions—Migration Station
http://www.nationalgeographic.com/xpeditions/hall/index.html?node=36
National Geographic: Geography Action!—Migration: The Human Journey
http://ngsednet.org/community/index.cfm?community_id=7
National Geographic: The Genographic Project
http://www.nationalgeographic.com/genographic/index.html
National Geographic: Xpeditions—Migration: Why People Move
http://www.nationalgeographic.com/xpeditions/lessons/09/g68/tgmigration.html

Continent

From Wikipedia, the free encyclopedia

Animated, color-coded map showing various continents and regions. Depending on the convention and model, some continents may be consolidated or subdivided: for example,Eurasia is often subdivided into Europe and Asia (red shades), while North and South America are sometimes recognized as one American continent (green shades).

A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are (from largest in size to smallest): Asia, Africa, North America, South America,Antarctica, Europe, and Australia.^[1]

Plate tectonics is the geological process and study of the movement, collision and division of continents, earlier known as continental drift.

Residents of Britain and Ireland sometimes refer to Continental Europe, that is, the mainland of Europe, excluding the British Isles,^[2] Icelandand some other islands, as "the Continent".

Continent

From Wikipedia, the free encyclopedia

Animated, color-coded map showing various continents and regions. Depending on the convention and model, some continents may be consolidated or subdivided: for example,Eurasia is often subdivided into Europe and Asia (red shades), while North and South America are sometimes recognized as one American continent (green shades).

A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are (from largest in size to smallest): Asia, Africa, North America, South America,Antarctica, Europe, and Australia.^[1]

Plate tectonics is the geological process and study of the movement, collision and division of continents, earlier known as continental drift.

Residents of Britain and Ireland sometimes refer to Continental Europe, that is, the mainland of Europe, excluding the British Isles,^[2] Icelandand some other islands, as "the Continent".

HOW TO USE COMPASS

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).

A magnetic compass points to magnetic north pole, which is approximately 1,000 miles from the true geographic North Pole. A magnetic compass's user can determine true North by finding the magnetic north and then correcting for variation and deviation. Variation is defined as the angle between the direction of true (geographic) north and the direction of the meridian between the magnetic poles. Variation values for most of the oceans had been calculated and published by 1914.^[81] 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. 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. They then pointed their ship to the next compass point and measured again, graphing their results. In this way, correction tables could be created, which would be consulted when compasses were used when traveling in those locations.

Mariners are concerned about very accurate measurements; however, casual users need not be concerned with differences between magnetic and 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 direction than expected over short distances, provided the terrain is fairly flat and visibility is not impaired. 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.^[74]

Soldier using a prismatic compass to get an azimuth.

Compass navigation in conjunction with a map (terrain association) requires a different 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 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.^[74] 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.^[74] In the given example, the large mountain in the second photo was selected as the target destination on the map. Some compasses allow the scale to be adjusted to compensate for the local magnetic declination; if adjusted correctly, the compass will give the true bearing instead of the magnetic bearing.

The modern hand-held protractor compass always has an additional direction-of-travel (DOT) arrow or indicator inscribed on the baseplate. 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 atrue bearing. 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 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.

Compasses are to be laid down on a leveled surface so the needle could point to the magnetic north more accurately, as to that the needle only rests or hangs on a bearing fused to the compass casing , if used at a tilt , the needle might hit the casing on the compass , and hence , not move. This will give a faulty reading . 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 not contacting the casing of the compass. If the needle tilts to one direction , tilt the compass slightly and gently to the opposing direction until the compass needle is horizontal , lengthwise. Items to avoid around compasses are magnets of any kind and any electronics. Magnetic fields from electronics can easily disrupt the needle , avoiding it from pointing with the earth's magnetic fields, causing interference. The earth's natural magnetic forces are considerably weak , measuring at 0.5 Gauss and magnetic fields from household electronics can easily exceed it , overpowering the compass needle. Exposure to strong magnets , or magnetic interference can sometimes cause the magnetic poles of the compass needle to differ or even reverse. Avoid iron rich deposits when using a compass , for example , certain rocks which contain magnetic minerals , like Magnetite.This is often indicated by a rock with a surface which is dark and has a metallic luster, not all magnetic mineral bearing rocks have this indication. To see if a rock or an area is causing interference on a compass , get out of the area , and see if the needle on the compass moves. If it does , it means that the area or rock the compass was previously at/on is causing interference and should be avoided.

HOW TO USE COMPASS

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).

A magnetic compass points to magnetic north pole, which is approximately 1,000 miles from the true geographic North Pole. A magnetic compass's user can determine true North by finding the magnetic north and then correcting for variation and deviation. Variation is defined as the angle between the direction of true (geographic) north and the direction of the meridian between the magnetic poles. Variation values for most of the oceans had been calculated and published by 1914.^[81] 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. 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. They then pointed their ship to the next compass point and measured again, graphing their results. In this way, correction tables could be created, which would be consulted when compasses were used when traveling in those locations.

Mariners are concerned about very accurate measurements; however, casual users need not be concerned with differences between magnetic and 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 direction than expected over short distances, provided the terrain is fairly flat and visibility is not impaired. 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.^[74]

Soldier using a prismatic compass to get an azimuth.

Compass navigation in conjunction with a map (terrain association) requires a different 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 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.^[74] 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.^[74] In the given example, the large mountain in the second photo was selected as the target destination on the map. Some compasses allow the scale to be adjusted to compensate for the local magnetic declination; if adjusted correctly, the compass will give the true bearing instead of the magnetic bearing.

The modern hand-held protractor compass always has an additional direction-of-travel (DOT) arrow or indicator inscribed on the baseplate. 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 atrue bearing. 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 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.

Compasses are to be laid down on a leveled surface so the needle could point to the magnetic north more accurately, as to that the needle only rests or hangs on a bearing fused to the compass casing , if used at a tilt , the needle might hit the casing on the compass , and hence , not move. This will give a faulty reading . 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 not contacting the casing of the compass. If the needle tilts to one direction , tilt the compass slightly and gently to the opposing direction until the compass needle is horizontal , lengthwise. Items to avoid around compasses are magnets of any kind and any electronics. Magnetic fields from electronics can easily disrupt the needle , avoiding it from pointing with the earth's magnetic fields, causing interference. The earth's natural magnetic forces are considerably weak , measuring at 0.5 Gauss and magnetic fields from household electronics can easily exceed it , overpowering the compass needle. Exposure to strong magnets , or magnetic interference can sometimes cause the magnetic poles of the compass needle to differ or even reverse. Avoid iron rich deposits when using a compass , for example , certain rocks which contain magnetic minerals , like Magnetite.This is often indicated by a rock with a surface which is dark and has a metallic luster, not all magnetic mineral bearing rocks have this indication. To see if a rock or an area is causing interference on a compass , get out of the area , and see if the needle on the compass moves. If it does , it means that the area or rock the compass was previously at/on is causing interference and should be avoided.

MODERN COMPASSES

Modern compasses

A liquid-filled compass with a lanyard for the neck

Modern compasses usually use a magnetized needle or dial inside a capsule completely filled with fluid (oil, kerosene, or alcohol is common). While older designs commonly incorporated a flexible diaphragm or airspace inside the capsule to allow for volume changes caused by temperature or altitude, modern liquid compasses utilize smaller housings and/or flexible materials for the capsule itself to accomplish the same result. 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, as well as other key points are often marked withphosphorescent, photoluminescent, or self-luminous materials^[73] to enable the compass to be read at night or in poor light.

Many modern recreational and military compasses integrate a protractor with the compass, using a separate magnetized needle. In this design the rotating capsule containing the needle has a transparent base containing map orienting lines as well as an orienting 'box' or outline for the needle.^[74] The capsule is then mounted in a transparent baseplate containing a direction-of-travel (DOT) indicator for use in taking bearings directly from a map.^[74]

Liquid filled lensatic compass

Cammenga air filled lensatic compass

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.^[74]

The military forces of a few nations, notably the United States Army, continue to utilize lensatic field compasses with magnetized compass dials or cards instead of needles. A lensatic-card compass permits reading the bearing off the compass card with only a slight downward glance from the sights (see photo), but may require a separate protractor for use with a map.^[74][75] The official U.S. military lensatic compass does not use fluid to damp needle swing, but ratherelectromagnetic induction to damp the needle. 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.^[76]

Some military compasses, like the U.S. SandY-183 (name derived from Stocker & Yale) military lensatic compass, the Silva 4b Militaire, and the Suunto M-5N(T) contain the radioactive material tritium (3H) and a combination of phosphors.^[77] The U.S. military compass, made by Stocker & Yale (later, Cammenga) contained 120 mCi (millicuries) of tritium. The purpose of the tritium and phosphors is to provide illumination for the compass, via radioluminescent tritium illumination, which does not require the compass to be "recharged" by sunlight or artificial light.^[78]

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. This preserves the horizontal position.

[edit]Thumb compass

Main article: Thumb compass

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. 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.

[edit]Gyrocompass

Main article: 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 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.g. trees, that can block the reception of electronic signals.

[edit]Solid state compasses

Main article: Magnetometer

Small compasses found in clocks, mobile phones, and other electronic devices are solid-state compasses, usually built out of two or three magnetic field sensors that provide data for a microprocessor. The correct heading relative to the compass is calculated using trigonometry.

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. The sensor uses highly calibrated internal electronics to measure the response of the device to the Earth's magnetic field.

GPS receivers using two or more antennae can now achieve 0.5° in heading accuracy (e.g.^[79]) and have startup times in seconds rather than hours for gyrocompass systems. Manufactured primarily for maritime applications, they can also detect pitch and roll of ships.

[edit]Specialty compasses

A standard Brunton Geo, used commonly by geologists

Apart from navigational compases, 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. This compasses ordinarily uses a liquid-damped capsule^[80] and magnetized floating compass dial with an integral optical (direct or lensatic) or prismatic sight, often fitted with built-in photoluminescent or battery-powered illumination.^[74] 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 high-quality needles and jeweled bearings, and many are fitted for tripod mounting for additional accuracy.^[74]
• 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.