A bearing compass, is a nautical instrument used to determine the bearing of observed objects. (Bearing: angle formed by the north and the visual to a certain object in the sea or ashore). Used in navigation to determine the angle between the direction of an object and the magnetic north or, indirectly relative to another reference point. Provides the absolute bearing, which is the clockwise angle between

magnetic north The north magnetic pole, also known as the magnetic north pole, is a point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downward (in other words, if a magnetic compass needle is allowed t ...

true north True north is the direction along Earth's surface towards the place where the imaginary rotational axis of the Earth intersects the surface of the Earth on its Northern Hemisphere, northern half, the True North Pole. True south is the direction ...

and the object. For example, an object to the east would have an absolute bearing of 90º, if it is relative to the magnetic north than it is called magnetic bearing. It is commonly used by geologists and surveyors to obtain precise bearings on the ground.

Sailors A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor'' ...

use successive demarcations of fixed reference points along with simple geometric techniques to determine their position, course and speed. In addition, making successive demarcations of other vessels, together with simple geometry techniques, can help the navigator to determine if there is a risk of collision and to decide what measures should be taken to avoid the danger.

Description

All hand compasses can be used to take bearings, but what distinguishes the bearing compass from the rest is the fact that it has some type of optics to allow viewing "at the same time" the compass marks and the observed target. The simplest and most common type of hand compass has a horizontal

compass rose A compass rose or compass star, sometimes called a wind rose or rose of the winds, is a polar coordinates, polar diagram displaying the orientation of the cardinal directions (north, east, south, and west) and their points of the compass, inter ...

and an observation device: a

pinnule A leaflet (occasionally called foliole) in botany is a leaf-like part of a compound leaf. Though it resembles an entire leaf, a leaflet is not borne on a main plant stem or branch, as a leaf is, but rather on a petiole or a branch of the leaf. C ...

alidade An alidade () (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. This task can be, for example, to Triangulation (surveying), tr ...

viewfinder In photography, a viewfinder is a device on a camera that a photographer uses to determine exactly where the camera is pointed, and approximately how much of that view will be photographed. A viewfinder can be mechanical (indicating only direct ...

that allows the user to observe the target and then by "changing view", read the angle formed by the target's direction and the one marked by the compass with respect to the

. More complex prismatic versions, such as

SUUNTO Suunto Oy is a Finland, Finnish company that manufactures and markets sports watches, dive computers, compasses and precision instruments. Headquartered in Vantaa, Finland, Suunto employs more than 300 people worldwide, and its products are sold ...

compasses (see first photograph), use an optical system to display the bearing marks through an ocular while pointing to the target.

Monocular Bearing Compass

There are also some models of monoculars/

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

, with electric lighting or without, which by means of an hybrid optical system (some of them electronic-digital) allow the bearing marks to be viewed at the same time as the object is observed through its optical system.

Types

* Monocular with zoom: this type has variable magnification, allowing the observation of objects at a wide range of distances, with the possibility to zoom in, adjusting the magnification to particular needs.. * Monocular with rangefinder: this type also includes a reticle to estimate distances

Characteristics

* Magnification: Compass monoculars are produced with different magnifications. For example, the model 8x25 monocular means that has a magnification x8, making the image twice bigger than a model 4x25 monocular * Diameter of the outer lens: The diameter of the front lens influences the amount of light that enters into the lens. For example, an 8x42 monocular with a 42mm front lens diameter, it's almost twice more luminous than a 8x25 with a 25mm front lens diameter

References

Bibliography

* Avery, T.E., Burkhart, H.E., ''Forest Measurements'', 5th ed. New York:McGraw-Hill (2002) * Johnson, Mark, ''The Ultimate Desert Handbook: A Manual for Desert Hikers, Campers, and Travelers'', McGraw-Hill Professional (2003), , 9780071393034 * Mooers Jr., Robert L. ''Finding Your Way In The Outdoors'', Outdoor Life Press (1972), * Rutstrum, ''The Wilderness Route Finder'', University of Minnesota Press (2000),

External links

historytoday.com
{{Orienteering, type=collapsed Forest modelling Navigational equipment Hiking equipment Orientation (geometry) Measuring instruments Orienteering