38.6 Distance on the Earth

38.6.2 Define units of distance used on aviation charts and the basis for these units.

In aviation, the primary units of distance used on charts are nautical miles and statute miles.

1. Nautical Miles:

A nautical mile is based on the circumference of the Earth and is defined as one minute of latitude.

One nautical mile is equivalent to approximately 1.15078 statute miles or 1.852 kilometers.

Nautical miles are used in aviation because they provide a direct relationship to the Earth’s geometry, making it easier for pilots to navigate using latitude and longitude.

2. Statute Miles:

Statute miles are the standard miles used in the United States for land-based measurements, defined as 5,280 feet or approximately 1.609 kilometers.

While statute miles can be found on some aviation charts, they are less common than nautical miles in aviation contexts.

38.6.4 Explain the distance calculation basis used by GNSS and FMC systems.

GNSS (Global Navigation Satellite System) and FMC (Flight Management Computer) systems calculate distance based on the principles of triangulation and satellite positioning.

1. GNSS Distance Calculation:

GNSS systems use a network of satellites that transmit signals to receivers on the ground or in aircraft.