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Discussion: Azimuth vs. Bearing

in: Orienteering; General

Sep 11, 2006 4:38 PM # 
Could someone please explain to me what the difference is between an azimuth and a bearing? The two terms are used interchangeably sometimes but I know they're not the same. Thanks. I need to explain this to some middle school kids as part of a map-reading lesson.
Sep 11, 2006 4:48 PM # 
bearings can be done without a compass and thus are preferable...


orienteers don't do azimuths, adventure racers do (run due West for 3km or until you come back to where you started...)
Sep 11, 2006 5:07 PM # 
Hopefully somebody will put it more exactly, but in general, azimuth is not often mentioned and bearing seems to take on all roles (but arguably incorrectly).

Azimuth is a noun and bearing is more commonly the verb.

"I am bearing west on my 270 degree azimuth"

Also, an azimuth is explicitly related to a horizontal angle whereas a bearing (such as celestial) can imply other planes.

They overlap enough though that I've never heard someone ask what my azimuth was...

Sep 11, 2006 5:08 PM # 
Essentially synonymous depending on the context, although "azimuth" is less ambiguous because the word doesn't have other meanings, and it typically refers to "degrees clockwise from due south", whereas "bearing" is a more general term refering to relative angle of direction.

At least, that's what my dictionary suggests. I avoid both terms equally.
Sep 11, 2006 6:48 PM # 
All I know is they shoot 'em down in Texas.
Sep 11, 2006 7:00 PM # 
Is there anything they don't shoot down in Texas?
Sep 11, 2006 7:31 PM # 
I always just assumed it was a Canadian/American thing. First event in the states I went to I heard what I had always known as a "safety bearing" being referred to as a "panic azimuth"
(and of course, as with whistles, no one outside of NA knows what either is about)
Sep 11, 2006 7:50 PM # 
Texans shoot everything, even their friends. Oh wait, he's from Wyoming. Well, I guess if dubya was there, he would have shot him too.
Sep 11, 2006 7:51 PM # 
Where was said 'panic azimuth' to be shot? Texas?

Whistles have been required in some Australian championships that I've been to.
Sep 11, 2006 11:50 PM # 
Any Land Surveyor knows...
Azimuths are expressed as an angular measurement from a meridian (usually north) and measured clockwise. The angular measurement will range through a full circle, most commonly expressed as 0°-360° measured clockwise.
Bearings are expressed as an angular measurement with a given quadrant, such as North 36° 47' East. The angular portion will reference the acute (less than 90°) angle from the North or South meridian as measured to the East or West.
Sep 12, 2006 1:26 AM # 
Are you guys making up words?
Sep 12, 2006 1:34 AM # 
The difference is that azimuth has a really cool etymology (Old French < Arabic but the Arabic word is probably an Indo-European loan originally) whereas bearing is boring common or garden Anglo-Saxon.
Sep 12, 2006 11:47 AM # 
Around here I think "bearing" is wandering around in all directions looking for bears.
Sep 12, 2006 5:24 PM # 
New Hampshireans tend to shoot bearings, not those Texan azimuths.
Sep 12, 2006 6:44 PM # 
From Wikipedia:

"In navigation, a bearing is the clockwise angle between a reference direction (or a datum line) and the direction to an object.

Unless otherwise specified, the reference direction is generally understood to be magnetic North, in which case the term compass bearing is also used.

If navigating by gyrocompass, the reference direction is true north, in which case the terms true bearing and geodetic bearing are used.

In stellar navigation, the reference direction is that of the North Star, Polaris.

Generalising this to two angular dimensions, a bearing is the combination of antenna azimuth and elevation required to point (aim) an antenna at a spacecraft. The bearing for geostationary satellites is constant. The bearing for polar-orbiting satellites varies continuously.

Moving from A to B along a great circle can be considered as always going in the same direction (the direction of B), but not in the sense of keeping the same bearing, which applies when following a rhumb line.

Accordingly, the direction at A of B, expressed as a bearing, is not in general the opposite of the direction at B of A.

For example, A and B on the northern hemisphere have the same latitude, and at A the direction to B is eastnortheast. Then going from A to B, one arrives at B with the direction eastsoutheast, and conversely, the direction at B of A is westnorthwest."

"Azimuth is the horizontal component of a direction (compass direction), measured around the horizon usually from the north toward the East, i.e. clockwise and is usually measured in degrees. Azimuth is often, some consider incorrectly, referred to as a bearing. In former times in astronomy it was more common to refer azimuth from the south, as it was then zero at the same time as the hour angle of a star was zero too. This assumes, however, that the star (upper) culminates in the south, which is only true for most stars in the northern hemisphere. In modern astronomy it is much more common to measure azimuth from the north.

In the horizontal coordinate system (also used in celestial navigation and satellite dish installation) azimuth is one of the two coordinates. The other is altitude (sometimes called elevation above the horizon). See also: sat finder.

In three-dimensional polar coordinate systems, including cylindrical coordinates and spherical coordinates, the azimuth of a point is the angle between the positive x-axis and the projection of a vector to the point onto the xy-plane. In cylindrical coordinates, theta θ is almost universally used to represent the azimuth. Although notation varies in spherical coordinates according to different conventions, the azimuth is usually either theta θ or phi φ.

In aviation, azimuth is used to determine headings or the direction in which to fly.

For magnetic tape drives, azimuth refers to the angle between the tape head(s) and the tape medium."
Sep 12, 2006 10:26 PM # 
"In stellar navigation, the reference direction is that of the North Star, Polaris. " --- That goes against everything I know about celestial navigation, which isn't much. Those guys juggle so many coordinate systems it makes my head spin.

This discussion thread is closed.