What’s the difference between an Azimuth and a Bearing?
Is it azimuth or bearing? Some people when using a compass to navigate will use either, so they (in this case only) mean the same and, as long as every understands which direction is being referred to, it really doesn’t matter.
How was that? The shortest blog ever.
Hmmmmm, not really much of a blog was it?
So let’s dig a little deeper.
The first thing to mention is that here I’m talking about navigating over the countryside with a map and compass. In this case we don’t need to worry about where the horizon is, spherical coordinates or do any complicated maths.
Why is this important? Well because azimuths can also be used in a 3d fashion, for example in astronomy to give the location of a star or in surveying for heights, etc.
To understand azimuths you need to learn (or remember from your school maths lessons) a short phrase which is “a reference meridian”, which is simply a line from one point to another. It could be from where you are to somewhere else or it could be from a point in the distance to another point.
So it is a straight line from somewhere to somewhere else and the angle between the line and something else is called the azimuth.
Remember you can use any line. Let’s say you are walking along the edge of a forest or a lake, it doesn’t matter which direction the forest or lake is pointing as you can say something like “we will stop at the pub, 2km away on an azimuth of 245 degrees from here”. This means that if you walk at 245 degrees (clockwise) from your current location on the edge of the forest or lake, for 2km, you will arrive at the pub. As you can see the reference meridian line can be pointing in any direction.
Azimuths are always quoted from 0 to 360 degrees clockwise from a reference meridian.
Remember we a talking about map and compass walking navigation here. This is important as technically a bearing is never more than 90 degrees. This is as (again in a purely technical sense) you would use two letters and an angle. The letter defines the quadrant of the circle e.g. NE (somewhere between North and East), SW (somewhere between South and West), etc. You then add in the angle. e.g. N28E, W86N, etc.
Of course when we’re talking about map reading and navigation over the British countryside we don’t do that, we simply use the full circle of 0 to 360 degrees. I’ll say it again, as long as you can navigate safely in this manner and, if you’re walking with others, that they understand it, it really makes no difference which method you use.
So, in our case, bearings are always taken from the North and can go either counter-clockwise or clockwise.
If you assume that North is 0 degrees and a full circle has 360 degrees, you will give a bearing with reference to how far around the circle the direction is.
You can go forward or backwards with bearings.
So you can say a bearing of 123 degrees – which would mean 123 degrees clockwise from North. You can also say “I’m going West 30 degrees – which means you are walking at an angle of 30 degree counter-clockwise from North. Or you could just say I’m going East – which would be a bearing of 90 degrees.