GEN 2.1 Measuring System, Aircraft Markings, and Holidays

1.. Units of Measurement

  1. The following table identifies the units of measurement that have been selected for use in messages ­transmitted by all U.S. aeronautical stations, in the U.S. AIP, NOTAM dissemination, and other publications.

2.. Time System

  1. Coordinated Universal Time (UTC) is used in the Air Traffic and Communication services provided and in ­most documents published by the Aeronautical Information Services.
  2. When local mean time is used, it will be so indicated as local standard time (LST). See FIG GEN 2.1-1 for ­a depiction of the standard time zones within the continental U.S.

3.. Geodetic Reference Datum

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

4.. Vertical Reference System

  1. The U.S. utilizes Geoid-03, which is a component of the North American Vertical Datum of 1988 (NAVD ­88).

5.. Aircraft Nationality and Registration Marks

  1. The nationality mark for the aircraft registered in the U.S. is the letter N, followed by a series of numbers ­or a series of numbers and letters.

6.. Public Holidays

  1. A list of US public holidays can be found at www.usa.gov/holidays. Aviation services remain available ­during holidays.
    TBL GEN 2.1-1

    For Measurements of:

    Units used:

    Distance used in navigation, position reporting, etc. - generally in ­excess of 2 to 3 nautical miles

    Nautical miles and tenths

    Relatively short distances such as those relating to aerodrome (e.g., ­runway lengths)

    Feet

    Altitudes, elevations and heights

    Feet

    Horizontal speed, including wind speed

    Knots

    Vertical speed

    Feet per minute

    Wind direction for landing and taking off

    Degrees magnetic

    Wind direction except for landing and taking off

    Degrees true

    Visibility, including runway visual

    Statute miles or feet

    Altimeter Setting

    Inches of mercury

    Temperature

    Degrees Fahrenheit

    Weight

    Pounds

    Time

    Hours and minutes, the day of 24 hours ­beginning at midnight Coordinated Universal ­Time

    FIG GEN 2.1-1
    FIG GEN 2.1-1