Compass Bearings and Headings Made Simple

Direction is the language of navigation, and the compass is how we speak it. Whether you are steering a course, taking a bearing on a lighthouse, or reporting the direction of another vessel, you are working with angles measured in degrees around a full circle. Yet many newcomers stumble over three closely related ideas: bearings, headings, and the different kinds of north. This guide clears up the confusion so you can approach your boating exam with confidence.

At its heart the system is simple. A full circle contains 360 degrees, measured clockwise from north. North is 000 or 360, east is 090, south is 180 and west is 270. Everything else is a matter of applying small, predictable corrections.

Bearings Versus Headings

A heading is the direction in which your boat is pointing, the way the bow is aimed. A bearing is the direction from your boat to another object, such as a buoy, a headland or another vessel. These are two different things, and confusing them leads to real navigation errors.

Bearings come in two useful forms. A compass bearing or true bearing is measured relative to north and describes the absolute direction to an object. A relative bearing is measured relative to your own bow, so an object dead ahead has a relative bearing of 000, one directly abeam to starboard is 090, and one astern is 180. Being able to convert a relative bearing into a true bearing, by adding it to your heading, is a valuable skill for fixing your position.

The Three Norths

Here is the idea that trips up most students. There are three different norths, and knowing which one you are using matters enormously.

True north points to the geographic North Pole and is the reference used by charts. Magnetic north is the direction a compass needle actually points, toward the magnetic pole, which sits some distance away from the geographic pole and slowly moves over time. Compass north is what your particular compass shows once local magnetic influences on the boat are taken into account. The differences between these three are what all direction corrections are about.

Variation and Deviation

The angle between true north and magnetic north is called variation, sometimes written as magnetic variation. It differs depending on where you are in the world and changes gradually year by year. The value and its annual change are printed inside the compass rose on your chart, so you always have the local figure to hand.

The angle between magnetic north and compass north is called deviation. This is caused by the boat’s own magnetic influences, such as the engine, electronics and metal fittings, and it changes depending on which way the boat is heading. Deviation is recorded on a small table or curve made specifically for your vessel. Both variation and deviation are expressed as so many degrees east or west, and both must be applied when converting between true, magnetic and compass directions.

Converting Between True, Magnetic and Compass

Converting directions is a matter of adding or subtracting variation and deviation in the right order. A widely taught memory aid runs from true to compass adding westerly errors, often remembered as “true, variation, magnetic, deviation, compass”. A common reminder for the direction of correction is that when converting from true toward compass, you add westerly errors and subtract easterly ones, reversing the rule when going the other way.

The key is to be systematic. Write down each step: start with your true direction from the chart, apply variation to get magnetic, then apply deviation to get the compass course you actually steer. Work in reverse to turn a compass bearing back into a true bearing for plotting. In the boatingexamine course you can drill these conversions with worked examples until the sequence becomes automatic.

Using Bearings in Practice

Bearings are the raw material of position fixing. By taking a compass bearing on a known landmark and drawing the reverse of that line back from the object on the chart, you create a position line somewhere along which your boat must lie. Cross two or three such bearings and their intersection reveals your position.

Good practice is to choose objects that are widely spaced in angle, ideally around 60 to 90 degrees apart, so the position lines cross cleanly. Take your bearings quickly one after another, correct them from compass to true, and plot them without delay so your fix reflects a single moment in time.

FAQ

What is the difference between variation and deviation? Variation is the natural angle between true north and magnetic north, which depends on your geographic location. Deviation is caused by magnetic influences aboard your own boat and changes with the vessel’s heading. Both must be applied when converting directions.

How do I turn a relative bearing into a true bearing? Add the relative bearing to your true heading. If an object lies 30 degrees to starboard of the bow and your heading is 100 true, its true bearing is 130. If the total exceeds 360, subtract 360.

Why do charts show two compass roses or two arrows? Many compass roses display both true north and magnetic north, along with the local variation and its yearly change. This lets you read or plot bearings in whichever reference you need without extra calculation.