3.1 Name/designation of system

All published geographical coordinates indicating latitude and longitude are expressed in terms of the World Geodetic System-1984 (WGS-84) geodetic reference datum.

3.2 Parameters of the Projection

Projection is expressed in term of Universal Transverse Mercator (UTM).

For measurement of	Units used
Distance used in navigation, position reporting, etc...	Kilometres or Nautical miles
Relatively short distances such as those relating to aerodromes (e.g. Runway lengths)	Metres
Altitudes, elevations and heights	Metres or feet
Horizontal speed including wind speed	Metre per second or metre per knots
Vertical speed	Metre per second
Wind direction for landing and taking-off	Degrees Magnetic
Wind direction (except for landing and taking-off)	Degrees true
Visibility including runway visual range	Kilometres or metres
Altimeter setting	Hectopascal
Temperature	Degrees Celsius
Weight	Metric tonnes or kilograms
Time	Hours and minutes, beginning at midnight UTC

3.3 Ellipsoid

Ellipsoid is expressed in terms of the World Geodetic System-1984 (WGS-84) ellipsoid.

3.4 Datum

The World Geodetic System-1984 (WGS-84) is used.

3.5 Area of application

The area of application for the published geographical coordinates coincides with the area of responsibility of the Aeronautical Information Service, i.e. the entire territory of Viet Nam as well as the airspace over the high seas encompassed by Ha Noi and Ho Chi Minh flight information regions.

3.6 Use of an asterisk to identify published geographical coordinates

An asterisk (*) will be used to identify those published geographical coordinates that have been transformed into WGS-84 coordinates but whose accuracy of their original field work does not meet the accuracy requirements in ICAO Annex 11, Chapter 2 and ICAO Annex 14, Volumes I and II, Chapter 2.

4.1 Name/designation of system

The vertical reference system corresponds to mean sea level (MSL).

4.2 Geoid model

The geoid model used is the Earth Gravitational Model 1996-(EGM-96).