In navigation, what's the difference between bearing, heading, direction, and course?

Question

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.

Answer 1

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 (left) and starboard (right) are always relative to the bow (front of the vessel).

Heading is the direction your face/nose/front/bow is currently pointing at (relative to true north), assuming default movement by your vehicle's impulse mechanism is forward. If there are no obstacles between you and your destination, and nothing aside from your vehicle's own impulse mechanism is moving it, heading should always be equal to bearing.

Course describes the entire planned route to get to your destination. A course correction implies that your planned route encountered an obstacle, and that you have to correct that plan.

As an example, let's assume a car is the vehicle, and it's navigating in a standard grid-like street structure. If you're at point (0, 0) with your car facing north and your destination is at (3, 3), your course would be "Three blocks north, then three blocks east". Your bearing at the start of your journey would be north-east, and your heading would be north, since that's the way your car is facing.

After you travel three blocks north, you're stopped at a red light. You should plan to turn right, to change your heading to east, since your bearing is now east. Your remaining course is "3 blocks east".

In aviation, where winds can and often will push you off-course, heading is rarely equal to bearing when the total travel distance is large. This makes for frequent course corrections to account for wind.

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."

Answer 2

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.

Answer 3

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.

Answer 4

*

"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.

Answer 5

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