Bearings, azimuths, and symmetry

Bearings are a way of talking about directions using angles.  This is very useful for people in ships or planes, because you can use bearings to tell them the direction they need to travel in.  Also, you can use bearings to tell them in which direction there are other planes or ships.  Bearings can be used to tell a ship which direction there is land (which they don’t want to hit), or to tell a plane the direction to a mountain (which they also don’t want to hit).

There are two main ways to describe the direction.

Azimuths

Azimuths describe a direction as being somewhere between 0 and 360 degrees.  0 degrees is the direction north, which is usually ‘up’ when you draw it on a piece of paper.  The angles increase as you travel in a clockwise direction from north.

Bearings

Sometimes these are also called surveyor bearings.  Bearings use a combination of angles and compass directions to describe a direction.  A direction is described by how far towards east or west it is from north or south.  So the first thing you need to do is work out which horizontal half – the top or bottom – the direction is in.  If it’s in the top half, you’ll describe how far away from north it is.  If it’s in the bottom half, you’ll describe how far away from south it is.

The second thing you need to do is work out which vertical half the direction is in.  If it’s in the left half, you describe how far towards west it is.  If it’s in the right half, then you describe how far towards east it is.

The general description of a bearing is:

                                      … degrees east / west of north / south

So it’s either east or west, and either north or south.

Here’s an example:

First thing we need to do is work out whether it’s in the top or bottom half.  It’s obviously in the top half, so we’ll be describing how far away from north it is.  So we can write something like:

                                         Bearing is … degrees …. of north

Second thing to do is work out whether it’s in the left or right half.  It’s in the left half, so we’ll be using west:

                                        Bearing is … degrees west of north

So now all we’ve got to do is provide the number of degrees.  Well, if we start at north, and rotate towards west until we reach our direction, how many degrees have we rotated?  Luckily, it’s already marked on the diagram - 41°.  So we can write:

                                        Bearing is 41° degrees west of north

Clockwise and anti-clockwise

If you stand or sit on a merry go round, and have a friend pushing you, there are two directions you can spin in.  There are two words describing these directions – clockwise and anti-clockwise.  To remember which word refers to which direction, it’s easiest to go back to where these words came from – the clock.

Clockwise is the direction that the hour and minute (and second) hands on a clock normally travel in.  Anti-clockwise is the opposite direction to clockwise.  You can think of anti-clockwise as being ‘anti’ or ‘against’ the direction of clockwise.