Editing Compass (section)

== Variants ==
[[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 [[transparency (optics)|transparent]] so that an orienteer can hold a [[Orienteering map|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.

[[File:Motorola Xoom - AKM Semiconductor AKM8975-1693.jpg|thumb|3-axis electronic magnetometer AKM8975 by [[AKM Semiconductor, Inc.|AKM Semiconductor]]]]

The [[earth inductor compass]] (or "induction compass") determines directions using the principle of [[electromagnetic induction]], with the [[Earth's magnetic field]] acting as the [[Electromagnetic induction|induction field]] for an [[electric generator]], the measurable output of which varies depending on orientation .<ref name="aero-digest">{{Cite journal|last=Goldsborough|first=Brice|date=June 1927|title=The Earth inductor compass|url=http://eaavintage.org/wp-content/uploads/2013/01/2005-Vol.-33-No.-04-The-Earth-Inductor-Compass.pdf|journal=Aero Digest}}</ref><ref>{{cite book|url=https://books.google.com/books?id=o2I1JWPpdusC&pg=PA370|quote=induction compass|title=Modern dictionary of electronics|isbn=978-0-7506-9866-5|last1=Graf|first1=Rudolf F|year=1999|publisher=Newnes }}</ref>

A vertical card magnetic compass installed in an airplane can eliminate some magnetic dipping errors while making the compass less confusing to read in the cockpit. The compass dial is driven by a set of gears controlled by a magnet mounted on a shaft. [[Eddy current]] induced into a damping cup also helps mitigate magnet oscillation.<ref name="IFH">{{cite book |title=Instrument Flying Handbook |date=2012 |publisher=[[Federal Aviation Administration]] Flight Standards Service  |edition=FAA-H-8083-15B |url=https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-15B.pdf |chapter=Chapter 5. Flight Instruments |pages=15}}</ref>

Small electronic compasses ([[Ecompass|eCompass]]es) found in clocks, [[mobile phone]]s, and other electronic devices are [[Solid-state (electronics)|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 [[microcontroller|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.

[[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:

* The [[Qibla compass]], which is used by Muslims to show the direction to Mecca for prayers.
* The optical or [[prismatic compass]], most often used by surveyors, but also by cave explorers, foresters, and geologists. These compasses generally use a liquid-damped capsule<ref>Kramer, Melvin G., {{US Patent|4175333}}, ''Magnetic Compass'', Riverton, Wyoming: The Brunton Company, pub. 27 November 1979: The ''Brunton Pocket Transit'', which uses magnetic induction damping, is an exception.</ref> and magnetized floating compass dial with an integral optical sight, often fitted with built-in photoluminescent or battery-powered illumination.<ref name=des113114>[[#Johnson|Johnson]], pp.  113–114</ref> 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.<ref name=des113114 />
* The [[trough compass]], 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.
* The [[luopan]], a compass used by feng shui practitioners.