What is the difference between an Azimuth and Bearing?

I use the words azimuth and bearing a lot.  I also hear people using them interchangeably quite often.  However, there is a difference.

Azimuth

When we use a compass to determine a direction, we are technically talking about an azimuth.  We use a reference of North as 0 and measure our direction using degrees clockwise from North (e.g. East is 90 degrees, South is 180 degrees, West is 270 degrees).  Our reference meridian can be true north, grid north, magnetic north, or an assumed north, but that is beyond the scope of this article.

Bearing

While we often use the word bearing the same way we use the word azimuth, that isn’t technically correct.  A bearing is described from North or South, and what angle to the East or West.  So, we can say we are 20 degrees East of South or more commonly S 20 E.  To put that in terms of an azimuth, we say 160 degrees.

Confusing enough?

Here is a simple way to convert from azimuth to bearing:

With 0 to 90 degree azimuth = 0 to 90 degree bearing

With 90 to 180 degree azimuth, your bearing = 180 – azimuth

With 180 to 270 degree azimuth, your bearing =  azimuth – 180

With 270 to 360 degree azimuth, your bearing = 360 – azimuth

For example, an azimuth of 296 degrees converts to a bearing of N 64 W.

Clearer?

Tags: Azimuth, bearing, compass, navigation