Units of measurement

2.1.1 Units of measurement

The following table of units of measurement wiil be used by aeronautical stations within Sofia FIR for air and ground operations.

For measurement of

Units used

Distances used in navigation, position reporting etc.

Kilometres, Nautical Miles and tenths*

Relatively short distances such as those relating to aerodromes (e.g. RWY land)


Altitudes, elevations and heights

Metres, Feet*

Horizontal speed

Kilometres per hour, Knots*

Vertical speed

Metres per second, Feet per minute*

Wind speed

Metres per second, Knots*

Wind direction for landing and take-off

Degree Magnetic

Wind direction except for landing and take-off

Degree True

Visibility including RVR

Kilometres or metres

Altimeter setting



Degrees Celsius (Centigrade)


Kilogrammes, Tonnes*


Hours and minutes, beginning at midnight UTC

Note: Units of measurement annotated by * are used as alternative in accordance with Regulation № 5 of the Ministry of Transport and Communications and ICAO Annex 5.