Directions are described as angles, starting at North and counting up in degrees going clockwise. Directions are written as 3 digits:
However, many cockpit instruments will abbreviate them to one or two digits, e.g. 6 for 060° and 30 for 300°.
There are 3 different reference systems used so we need to be clear about which north we are talking about:
True North (T) is the Earth’s geographic north pole – the one at the ‘top of the Earth’. Any direction measured on a chart is relative to true north.
A direction measured from true north is usually expressed in degrees true. For example, East measured on a chart is called 090° True or 090°T.
The magnetic north pole is where a magnetic compass will point towards. This comes from the strong magnetic field that surrounds the Earth, as if there were a magnet inside the Earth.
Directions measured relative to magnetic north are expressed in degrees magnetic (°M). For example, Magnetic East is 90° clockwise from the magnetic north pole and is called 090° Magnetic or 090°M.
The magnetic north pole is located in Canada and moves very slightly each year.
Aircraft are fitted with a magnetic compass, which sits inside a case filled with liquid. The liquid dampens any disturbances in flight and reduces friction so the compass is free to align with Earth’s magnetic field.
For various reasons discussed in the next lesson, the compass will not always perfectly point to magnetic north.