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Specifically, in real-world use, I would think that "course" and "heading" tend to imply a vector of movement, while "bearing" and "direction" might refer only to which way one is facing.

I am looking for two words to correctly assign to these physical components of a vehicle. I suppose I may be looking for military, or naval terminology.

For example, if you were in a submarine, being buffeted by currents, so your vessel was being pushed sideways, how would you correctly say, "we are being pushed east but we are facing north?" Would it be correct to say "we are bearing 0°, but our heading is 270°?" It doesn't sound correct.

Edit

As I note in a comment below: when I clumsily wrote that I was "looking for two words to correctly assign to these physical components of a vehicle," what I meant was, single-word attributes to distinguish between the direction a vehicle was facing, and the actual direction the vehicle was moving in, voluntarily or not.

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Title suggests a localized vocabulary! –  Kris Jan 14 '12 at 8:18

5 Answers 5

Bearing is regularly defined as the direction (relative to true north) in which your destination lies. If you could go in a straight line to your destination, this would be the most direct way of getting there.

You also have relative bearing, where the front of the vehicle is considered "north"; you'll see this when pilots claim, for example, that something is "at your 3 o'clock"; in naval terminology, port and starboard are always relative to the bow.

Heading is the direction you are currently navigating in. If there are no obstacles between you and your destination, heading would always be equal to bearing. Otherwise, for example, your bearing could be northwest while you are heading north, such that your heading and bearing are equal with no obstacles in between.

Course describes the entire planned route to get to your destination. In the above example, and assuming a grid-like street structure, your course could be "north 3 blocks, then west 3 blocks".

In my opinion, direction is the most basic term of all, and describes a directed vector between two points.

For your example, it seems like the proper phrasing would be "We are heading north, but we're being pushed off-course eastwards."

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Thanks — the distinction between bearing, heading, and course makes sense to me, although your definition of heading does not agree with jwpat7's. When I clumsily wrote that I was "looking for two words to correctly assign to these physical components of a vehicle," what I meant was, single-word attributes to distinguish between the direction a vehicle was facing, and the actual direction the vehicle was moving in, voluntarily or not. I think "orientation" might work for the former, but I'm not sure which, if any, of the words I listed could really be applied to non-voluntary motion. –  Nathan Jan 13 '12 at 22:26
    
There is almost always at least the Earth itself in the way. So even without obstacles, wind, and the like, heading and bearing differ on the shortest path, unless you're going directly up or tunneling through the Earth. –  David Schwartz Jan 14 '12 at 0:25
    
Heading is direction you are currently facing, which may not correspond the direction you are navigating in presence of currents (at sea) or wind (in the air). –  Jan Hudec Aug 4 at 9:43

Bearing is the direction to an external object, which is obviously an essential part of navigation. So "your bearing is 180 degrees" is not meaningful; "your bearing is 180 degrees from the lighthouse" is helpful (sometimes expressed as "0 degrees to the lighthouse", but that's another question).

Heading is what you are looking for to express the direction you are facing (I think Wikipedia's explanation is confusing; yes, it is expressed as an angle, but only when necessary to reduce it to numbers: 'heading due west' is perfectly normal.)

There is no single word to express the direction you are actually travelling in, probably because there are so many components (wind, leeway, current, pilot error...). Course made good or track over ground are probably closest.

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Thanks, great clarification! The Wikipedia article jwpat7 links to also says of aircraft that "due to wind forces, the direction of movement of the aircraft, or track, is not the same as the heading. The nose of the aircraft may be pointing due west… but a strong northerly wind will change its track south of west" which is much like my submarine example, and suggests that track alone may be the other word I want, meaning direction-craft-is-actually-going. It implies to me observed motion. –  Nathan Jan 13 '12 at 23:18

The notion that "heading tends to imply a vector of movement" is incorrect; as noted in Wikipedia, "Heading is the angle of the vessel, aircraft or vehicle to an object (e.g. true north)", and angles do not require or imply motion of an object.

Also as noted in Wikipedia, "In navigation, a vehicle's course is the angle that the intended path of the vehicle makes with a fixed reference object (typically true north)", and "The track or course over ground, is the actual path followed by the vessel" [italics added] and "The angle between heading and track is known as the drift angle or crab angle".

With that terminology understood, now consider "words to correctly assign to these physical components of a vehicle". The appropriate terms depend on kind of vehicle, but for an aircraft typically are roll, pitch, and yaw.

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*

"being buffeted by currents...your vessel was being pushed sideways, how would you correctly say, "we are being pushed east but we are facing north?"...

*A vessel or vehicle points where it points, that is the heading. It's course is the actual line it travels. So if your boat is facing north (navigational 0 degrees) and the currents are easterly (moving TO the east) thus pushing you off-track to the eastside of your intended track, you have to compensate for the current. This is done by steering your bow slightly into the oncoming current, in this case to port or slightly west of north. In a current of approximately 2 knots, you might have to compensate -10 degrees off bearing (your destination), say heading 350 degrees, so that your Course can remain due north at 0 degrees, where your "bearing" lies. That 10 degrees is a "drift" or "crab" angle, named that since crabs walk sideways, kind of like your ship is doing by heading differently from your true course/bearing.

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Heading is where you want to go. Bearing is the direction you are going.

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