Azimuth vs Bearing: What Is the Difference?
Two words for direction that often mean exactly the same thing, until a surveyor writes N 45 E and a navigator writes 045 and both are right.
What an azimuth is
An azimuth is a horizontal direction written as an angle: how far you turn clockwise from north to face something. North is 0 degrees, east is 90, south is 180 and west is 270, and every direction in between has its own number from 0 to 360.
The word comes from the Arabic as-sumut, "the directions", through medieval astronomy. Astronomers, navigators, surveyors, soldiers and radio engineers all use azimuths, because a single number says exactly which way to point with nothing left to interpret.
Bearing: the same idea, in several styles
In everyday navigation a bearing is simply an azimuth: an angle from 0 to 360 measured clockwise from north, usually written with three digits, so east is 090. If a hiking guide, a pilot or a sailing app gives you a bearing, you can treat it as an azimuth.
Surveyors and engineers often write bearings differently, as quadrant bearings. A quadrant bearing starts from north or south, gives an angle of no more than 90 degrees, and ends with east or west. N 45 E means "from north, turn 45 degrees towards east", which is the azimuth 045. S 45 E means "from south, turn 45 degrees towards east", which is the azimuth 135.
Ships and aircraft also use relative bearings, measured from the direction the vessel is pointing rather than from north. A relative bearing of 090 means "straight off the right-hand side", whatever the compass says.
Converting an azimuth to a quadrant bearing
Find which quarter of the compass the azimuth falls in, then measure from the nearer of north or south.
| Azimuth | Quadrant bearing | Example |
|---|---|---|
| 0 to 90 | N (azimuth) E | 060 becomes N 60 E |
| 90 to 180 | S (180 - azimuth) E | 135 becomes S 45 E |
| 180 to 270 | S (azimuth - 180) W | 200 becomes S 20 W |
| 270 to 360 | N (360 - azimuth) W | 300 becomes N 60 W |
Going the other way, read the first letter to know whether you start from north (0) or south (180), then add or subtract the angle.
Worked example: the back azimuth
From your tent, the azimuth to a lighthouse is 070 degrees. What azimuth would someone at the lighthouse use to look back at your tent?
- The back azimuth is the opposite direction, 180 degrees away
- If the azimuth is less than 180, add 180; otherwise subtract 180
- 070 + 180 = 250
The back azimuth is 250 degrees. Back azimuths are how you check a route in both directions, and how you plot your own position from a landmark.
Azimuths in the sky
Astronomers locate anything in the sky with two angles: its altitude, how high above the horizon it is, and its azimuth, which way along the horizon you face to see it. At the March and September equinoxes the Sun rises almost exactly due east, at an azimuth close to 90, nearly everywhere on Earth.
Away from the equinoxes the sunrise azimuth swings. In London in late June the Sun rises at an azimuth of around 50 degrees, well north of east, and in December it rises far to the south of east. Solar-panel installers and photographers look up sun azimuths for exactly this reason.
Azimuths in GeoAzimuth
In the GeoAzimuth game every arrow is an azimuth. The hidden city sits in the middle of the compass, and each arrow points at a real city at its true azimuth from the hidden one. Reading those numbers the way this lesson does, and remembering that long-distance azimuths follow the globe, is most of the skill.
Check what you learned
Five questions on azimuths and bearings. Pass at 70% or better to complete the lesson.
Practice with Games
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Azimuth vs bearing, in one paragraph
An azimuth is a horizontal angle measured clockwise from north, from 0 to 360 degrees: north is 0, east 90, south 180 and west 270. In most navigation a bearing means exactly the same thing and is written with three digits, so east is 090. Surveyors often use quadrant bearings instead, which start from north or south, turn no more than 90 degrees, and end with east or west, so the azimuth 135 is written S 45 E. A back azimuth points the opposite way and is found by adding or subtracting 180 degrees, which holds over short distances; across continents the shortest route curves over the globe and the two directions are no longer exactly opposite. Astronomers pair azimuth with altitude to locate objects in the sky, and the Sun rises close to an azimuth of 90 at the equinoxes.
Common questions about azimuths
What is an azimuth?
An azimuth is a direction expressed as an angle measured clockwise from north, from 0 to 360 degrees. North is 0, east is 90, south is 180 and west is 270. It is used in navigation, surveying, astronomy and radio, because one number describes a direction exactly.
Is an azimuth the same as a bearing?
Usually, yes. In navigation and map reading a bearing is an azimuth, written with three digits. The difference appears in surveying, where bearings are often written as quadrant bearings such as N 45 E, and on ships and aircraft, where a relative bearing is measured from the direction the craft is heading.
How do you calculate a back azimuth?
Add 180 degrees if the azimuth is less than 180, or subtract 180 if it is 180 or more. The back azimuth of 070 is 250, and the back azimuth of 300 is 120. Over very long distances on the globe the true reverse direction differs from this, because the shortest route curves.
How do I convert a quadrant bearing to an azimuth?
N x E is simply x. S x E is 180 minus x. S x W is 180 plus x. N x W is 360 minus x. So S 45 E is 135, S 20 W is 200 and N 60 W is 300.
What is the sun azimuth?
The sun azimuth is the compass direction of the Sun along the horizon, measured clockwise from north. It changes through the day and through the year: the Sun rises near azimuth 90 at the equinoxes, and much further north or south of east around the solstices, depending on your latitude.