The Earth
The Solar System & Time
Charts
Using Aeronautical Charts
Basics of Navigation
Distance, Speed & Time
Vertical Navigation
Fuel Planning
Practical Navigation Techniques
Radio Navigation
Practice Exam

Directions

Directions are described as angles, starting at North and counting up in degrees going clockwise. Directions are written as 3 digits:

90° clockwise from North is East, so East is 090°
180° clockwise from North is South, so South is 180°
270° clockwise from North is West, so West is 270°

However, many cockpit instruments will abbreviate them to one or two digits, e.g. 6 for 060° and 30 for 300°.

A Directional Indicator (DI) like this is found in typical training aircraft

There are 3 different reference systems used so we need to be clear about which north we are talking about:

True North
Magnetic North
Compass North

True North (°T)

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.

Magnetic North (°M)

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.

The difference between True North and Magnetic North is called Magnetic Variation

Compass North (°C)

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.

A typical magnetic compass found in training aircraft
The difference between Magnetic North and Compass North is called Magnetic Deviation or Compass Deviation