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Altimeter		An instrument that measures elevation by using barometric pressure (The pressure of air in the atmosphere).
Altitude		Distance above sea level.
Azimuth		Refers to the degree of bearing from your current position to another position. Azimuth means bearing. The direction from one position to another position. The set range of Azimuth is 0º to 360º.
Azimuth Ring		This refers to the ring formed by the top side of the Azimuth housing's outer edge. The Azimuth ring contains rule markings. These marking represent a scale of measure. The units of measure can be "degree", "mil", "quater quadrant" or a combination of these units. For navigation purposes the most common scale used is 0º to 360º degrees.
Azimuth Housing		This makes up the main body of the compass. The Azimuth housing contains the magnetic needle and the Azimuth ring. The housing rotates within the compass base to facilitate bearing readings.
Back Bearing		The 180-dregree opposite of the azimuth or bearing. Also know as back azimuth.
Back Sighting		The term used to refer to the action taken while establish a back bearing.
Base Plate		A see-through plate of an orienteering compass onto which, the compass housing is mounted.
Bearing		The direction from one position to another position. A bearing is stated in degrees and falls into a set range from 0º to 360º.
Bench Mark		A permanent object that is either natural or man-made and has a known elevation that can be used as a reference point when navigating.
Boxing The Needle		A term used to refer to the action of placing the red end of the magnetic needle exactly over the red end of the orienting arrow when determining a bearing. Since the orienting arrow is slightly larger than the magnetic needle, it appears to box the magnetic needle. This boxing action can also be referred to as "red on red" or centering" the needle.
Cardinal Points		The four main points of direction on a compass; North, 360 degrees; EAST, 90 Degrees; SOUTH, 180 degrees; WEST, 270 degrees.
Cardinal Direction		The four main points of direction on a compass; North, 360 degrees; EAST, 90 Degrees; SOUTH, 180 degrees; WEST, 270 degrees.
Clinometer		The Clinometer can be a device, or, a feature on a compass in which a measure of vertical angles can be taken; such as a slope of a hill. Clinometers can also be used as a level.
Contour Interval		The difference in elevation (height) between one contour line and the next. This interval is either expressed in feet or meters.
Contour Line		Found on topographical maps to indicate elevation of the land. Each contour line often comprises of an irregular closed loop that connects points of equal land elevation. The line with a darker shade of brown, typically every fifth line, is called an index contour and usually has the elevation printed on it. Elevations refer to elevation above sea level.
Curvimeter		The Curvimeter is an instrument used to measures straight and curved lines by hand. Measurement of angles, maps and drawings is made easy.
Declination		Declination is the error between true North and magnetic North. All maps are based on true North and all magnetic compass needles point to magnetic North. Current Magnetic Declination For Your Precise Location Computed Online Click Here While results are typically accurate to 30 minutes of arc, users should be aware that solar storms can cause intense, short-term disturbances in the earth's magnetic field. Today's Space Weather Report NOAA Space Report Related To GPS & Loran-C Users CLICK HERE Space Weather Alerts More Information: World Magnetic Model: information World Map Image
Declination Angle		The declination angle is the measure of angle between the bearings of true North and magnetic North. The declination angle is different all over the world. In the United States it varies by as much as 42 degrees from coast to coast. See Map Glossary For Current Magnetic Declination Data
Degree		A unit for measuring an angle or an arc of a circle. A circle is divided into 360 degrees. Degrees, when applied to the roughly spherical shape of the Earth for geographic and cartographic purposes, are each divided into 60 minutes.
Easting		A position on Earth is measured in meters using an easting & northing label. Easting provides east and west positioning from a zone meridian, and increases from left to right (east). A term used with UTM.
Fluid Damped		The magnetic needle of the compass is contained in a sealed, fluid filled, clear vial. The purpose of this fluid is to dampen or slow down the spinning action of the needle. This gives quicker and more accurate readings than can be had from cheaper, non-dampened compasses.
Geomagnetism		The study of geomagnetism is one of the oldest of the geophysical sciences. Since before the publication of William Gilbert's De Magnete in 1600, people have tried to unravel the mysteries of Earth's magnetic field. The National Geophysical Data Center maintains archives of geomagnetic data to further the understanding of Earth magnetism and the Sun-Earth environment. Geomagnetism Data - NOAA Satellite & Information Center
Graduations		The series of degree marking on the azimuth ring used for taking bearings.
Index Line		The point on a compass where the direction-of-travel arrow meets the Azimuth ring. At this point the degree reading should be read to establish a bearing.
Inclination		Lines of magnetic force vary from vertical at the magnetic poles, to horizontal near the equator. This vertical pulling force of the magnetic field is called Magnetic Inclination. Most compass needles must be balanced for this magnetic pull so the needle can freely move in the capsule. For a more detail and world compass zone chart Click Here. Because the Earth's magnetic field is constantly changing, it is impossible to accurately predict what the field will be at any point in the very distant future. Current Magnetic Inclination For Your Precise Location Computed Online Click Here
Latitude		The distance in degrees north and south from the equator. These lines run laterally (horizontally) around the globe and parallel to the equator. One minute of latitude equals 1 nautical mile.
Lensatic Compass		A compass which uses a retractable lens to read the bearing while simultaneously sighting an object.
Longitude		The distance in degrees east and west from the Prime Meridian established in Greenwich, England. These lines run vertically (lengthwise) around the globe and connect each pole.
Magnetic Declination		Magnetic declination is the difference between true and magnetic north. It is measured in degrees to the East or West of magnetic north. Declination angles vary throughout the world. Magnetic Field - Declination Computation Online - Click Here
Magnetic Inclination		Magnetic inclination is also sometimes called "magnetic dip". Magnetic inclination is the angle measured from the horizontal plane to the magnetic field vector (the directional pull of the magnetic force). Compass Inclination Details Click Here.
Magnetic Needle		The needle that points at magnetic north.
Magnetic North		The geographical region towards which all magnetic needles point. This point is approximately thirteen hundred miles south of true north and moves slightly each year. This movement is due to the earth's rotation and the friction created between its solid crust and liquid center.
Metadata		Metadata describe the content, quality, condition, and other characteristics of data. Data describing Data
Mirrored Compass		A compass which allows the user to simultaneously sight an object and align the orienting needle and magnetic needle.
MIL		Some compasses are offered with an optional azimuth ring with a "mil" scale. "Mil" is a unit of angle measure, used in the military for artillery settings. During World War II the U. S. Army often used a mil equal to 1/1000 of a right angle, 0.1 grad, 0.09°, or 5.4 arcminutes. More recently, various NATO armies have used a mil equal to 1/1600 right angle, or 0.05625° (3.375 moa).
Northing		A position on Earth is measured in meters using an easting & northing label. Northing provides north and south position from the Equator, and increases from bottom to top (north). A term used with UTM.
Orienteering		Orienteering refers to the practice of using a map and compass to determine route of travel.
Orienting Arrow		The orienting arrow is a permanent stationary marking in the Azimuth housing of a compass. The Orienting arrow is slightly wider than the magnetic needle and is used to frame the magnetic needle when establishing a bearing. Casanova's
Orienting Lines		Orienting lines are lines on the bottom of the compass housing that parallel the orienting arrow.
Prismatic Compass		A compass with a mirror designed to allow a user to see both distant objects being sighted and the compass face at the same time.
Protractor		An instrument used to determine and measure angles in degrees. A protractor can be useful when projecting magnetic lines across a map. A Protractor can be found as a built-in feature on a compass.
Quadrant		Some compasses are offered with an optional azimuth ring with a "Quadrant" scale. Quadrant is a unit of angle measure equal to 1/4 circle, pi/2 radians, 90°, or 100 grads. Definition 2 Quadrant is a unit of distance equal to the distance from the North Pole to the Equator. The metric system was originally designed to make this distance exactly 10 million meters (6213.71 miles). The actual meter comes close to the design. Using the conventional figures of 12756 kilometers for the equatorial diameter of the earth and 12714 kilometers for the polar diameter, and assuming the earth to have elliptic cross section, the length of the quadrant is about 10 001 300 meters (6214.52 miles). In principle, the quadrant is divided into 5400 nautical miles; in fact, 5400 international nautical miles equal 10 000 800 meters.
Radian (Rad)		Radian is a unit of angle measure widely used in mathematics and science. One radian, is the angle at the center of a circle, that cuts off an arc-of-length equal to the radius. Since the circumference equals 2 pi times the radius, one radian equals 1/(2 pi) of the circle, or approximately 57.295 779°. When angles are stated in radians, the constant pi tends to disappear from the equations, and this greatly simplifies calculation. For example, the length of an arc is simply its radius multiplied by its angular measure in radians, and the area of a sector of a circle is simply its angular measure in radians multiplied by half the square of the radius. The radian was defined and named by James Thomson in 1873. Thomson was a mathematics professor at Queen's College, Belfast, Northern Ireland, and the brother of the famous physicist William Thomson, Lord Kelvin.
Rule, Ruler		Also known as "ruler" or "scale". A system of marks at fixed intervals, used as a reference standard in measurement. Some compass companies refer to a ruler on a compass as a "rule" or "scale". When referring to a compass, the rule or scale, is a standard ruler of measured units. Common rulers on compasses would be measures of distance in: centimeters (cm); millimeters (mm); inches; meters; kilometers; yards; and miles.
Scale		1) The distance between two points on a map as they relate to the distance between those two points on the earth. 2) A proportion used in determining the dimensional relationship of a representation to that which it represents: a world map with a scale of 1:4,560,000. 3) When referring to a compass, the scale is a ruler of measure. A system of ordered marks at fixed intervals used as a reference standard in measurement. See Rule.
Sighting Line		Sometimes called the line of sight, the sighting line refers to the imaginary line that is used to sight along when reading a bearing.
Temperature		Numerical measures of heat or cold registered on a thermometer. The common measures (scales) of temperature are Fahrenheit and Celsius. Water freezes at 32 degrees Fahrenheit or 0 degrees Celsius.
Topographic		Of or having to do with topography or the physical features of a place.
Topographic Map		Also referred to as Topo Map. A topographic map is a 2-dimensional drawing of real, 3-dimentional terrain. Hills and valleys are represented through a series of contour lines. Each contour line has a specific, constant elevation. The vertical distance or height between the lines is stated on your map in feet or meters. The closer the contour lines are together, the steeper the actual terrain. The farther apart the contour lines, the flatter or more gradual the slope of the terrain.
Topography		The physical features of a place; or the study and depiction of physical features, including land elevations.
True North		(TN) The direction pointing to the geographic north; the North Pole.
UTM		Universal Transverse Mercator. A grid coordinate system, measured from the Equator (0º latitude) and a zone meridian. UTM divides the Earth into 60 zones, each with a meridian down the center. A position on Earth is measured in meters using an easting & northing label. More Details and How To Use & Read UTM - Click Here
U.S.G.S		U.S. Geological Survey - The USGS serves the Nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life. USGS Glossary
Waypoint		A checkpoint used as a point of reference when using electronic navigation instruments such as GPS or Loran.
Winchill		The calculation of temperature as affected by wind. Chart
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Compass Terms

COMPASS TERMS

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Radian (Rad)

Rule, Ruler

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