Heading is the direction your vessel or aircraft is pointed. Bearing is the direction from your position to a specific object or destination. They sound similar, but they measure fundamentally different things: heading describes where your nose is aimed, while bearing describes where something else sits relative to you or relative to north.
Understanding this distinction matters in both marine and aviation navigation, because the two numbers are often different, and confusing them can send you off course.
Heading: Where You’re Pointed
Heading is the direction your craft’s nose is facing, measured in degrees from north. If your ship’s bow is pointed due east, your heading is 090°. It’s a property of your vessel, not of any external object. And it changes constantly. As a ship yaws back and forth across its intended path due to waves or steering adjustments, the heading shifts moment to moment even though the general direction of travel stays roughly the same.
Heading can be expressed in three ways depending on which “north” you’re using as a reference. True heading uses geographic (true) north. Magnetic heading uses magnetic north, the direction a compass needle points. Compass heading adds a further correction for errors specific to your onboard compass. The formulas connecting them are straightforward: start with your desired true course, adjust for any wind correction angle to get true heading, then subtract or add the local magnetic variation to get magnetic heading, then correct for your compass’s own deviation to get compass heading.
The gap between true north and magnetic north is called magnetic declination, and it varies by location. The U.S. Geological Survey notes that the magnetic north pole sits roughly 1,200 miles from the geographic north pole. Along a line called the agonic line, the two norths align perfectly and declination is zero. West of that line in the U.S., a compass needle points east of true north. East of it, the needle points west. Ignoring this difference when converting between true and magnetic heading introduces real navigational error.
Bearing: Where Something Else Is
Bearing is the direction from you to another object, whether that’s a lighthouse, another vessel, a waypoint, or your destination. It comes in two flavors: absolute bearing and relative bearing.
Absolute bearing is measured clockwise from north (either true north or magnetic north) to the object. If a lighthouse sits due southwest of you, its absolute bearing is 225°. This number doesn’t change based on which way your boat is pointed. It only changes if you or the object move.
Relative bearing, on the other hand, is measured clockwise from your craft’s heading to the object. If your heading is 090° (due east) and a ship is directly off your right side, its relative bearing is 090° (90° clockwise from your bow). In maritime practice, relative bearings are often reported in plain language rather than degrees. A ship 45° off the right side of the bow is “green 45” or “45° on our starboard bow.” A vessel directly ahead is “dead ahead.” One 90° to the left is “on our port beam.” One 120° to the right is “on our starboard quarter.”
The key difference: absolute bearing is independent of your heading, while relative bearing is entirely dependent on it. Turn your ship, and every relative bearing changes even though nothing else has moved.
How Heading and Bearing Connect
If you know your heading and a relative bearing, you can calculate the absolute bearing by adding them together (and subtracting 360° if the result exceeds it). For example, if your heading is 270° and an object has a relative bearing of 045°, the absolute bearing to that object is 315°.
When you’re traveling in a straight line directly toward a destination with no wind or current, your heading and the bearing to that destination will be the same number. But that’s the exception, not the rule.
Why They’re Often Different
Wind and current are the main reasons heading and bearing diverge. Imagine you want to reach a port that bears 360° (due north) from your position. If a strong current is pushing you to the east, you’ll need to point your bow slightly west of north to compensate. Your heading might be 350°, while the bearing to the port remains 360°. The angle between your heading and your actual path over the ground is called the drift angle.
Marine navigators distinguish between two types of estimated position for exactly this reason. A dead-reckoning position uses the course steered and estimated speed through the water. An estimated position corrects that for the effects of current, wind, and other factors. The heading tells you where the boat is pointed, but not necessarily where it’s going.
In aviation, the same principle applies with crosswinds. A pilot may need to “crab” into the wind, pointing the aircraft’s nose slightly into the wind so that the actual ground track matches the desired bearing to the destination. The aircraft’s heading and the bearing to the airport will differ by the wind correction angle.
Course, Track, and Other Related Terms
Two other terms frequently get mixed in with heading and bearing: course and track. Course is the intended direction of travel through the water or air. Track (or course over ground) is the actual path your craft follows relative to the earth’s surface. A ship might have a heading of 350°, a course of 360°, and a track of 002° if the current wasn’t quite what the navigator expected.
Bearing stays distinct from all of these. Course, heading, and track all describe your movement. Bearing describes the direction to something external. If you’re navigating directly from one airport to another with no wind, your course and bearing to the destination will match. Add wind or current, and they start to separate, with heading diverging even further as you compensate.
How Each Is Measured
Heading is typically measured by instruments onboard your craft. A magnetic compass gives magnetic heading directly. A gyrocompass, which aligns with true north using the earth’s rotation rather than its magnetic field, gives true heading. Modern vessels and aircraft also use inertial measurement units combined with magnetometers, though magnetic sensors are susceptible to interference from nearby electronics, metal structures, or local magnetic anomalies. Calibration and filtering algorithms help correct for this, but heading accuracy from magnetic instruments is never perfect.
Bearing to an object can be measured with a handheld compass, a pelorus (a sighting device mounted on deck), radar, or GPS. Radar gives you both the bearing and distance to other vessels or landmarks. GPS provides bearing to a waypoint as a computed value based on coordinates rather than a physical measurement.
The practical takeaway: heading comes from what your craft is doing. Bearing comes from where something else is. Keeping that distinction clear is the foundation of competent navigation, whether you’re crossing an ocean or flying between cities.