Nautical Miles vs Statute Miles

Nautical Miles
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The Nautical Mile as a unit of measurement was first defined as an international standard in Monaco in 1929 at the First International Extraordinary Hydrographic Conference. Before that, there was no international standard for measuring distances in or over water. The U.S. jumped on board with this internationally-recognized measurement in 1954. 

In the aviation world, the standard measure of distance is the nautical mile.

However, there are still some measurements in aviation, such as the VFR visibilities and cloud clearance requirements, that report in statue miles (SM) rather than nautical miles (NM). Nevertheless, here are the definitions of each, along with a few easy conversions.

Distance Measurements

Statute Mile:

  • 1 SM = 1,609 meters
  • 1 SM = 5,280 feet
  • 1SM = .869 NM

 

Nautical Mile:

One nautical mile (NM) is defined by the NOAA as: “A unit of distance used in marine navigation and marine forecasts. It is equal to 1.15 statue miles or 1852 meters. It is also the length of 1 minute of latitude.”

  • 1 NM = 1,852 meters
  • 1NM = 6,076 feet
  • 1NM = 1.151 statute miles

In general, in aviation, distance is measured in nautical miles, with the exception of visibility, which is usually stated or forecasted in statue miles.

 

Speed Measurements

  • MPH: In statute miles, the speed measurements are given in miles per hour, such as in your vehicle.
  • Knot: The standard speed measurement in aviation is the knot, a derivative of the nautical mile. One knot is equal to one nautical mile per hour. Airspeed indicators on aircraft are calibrated in knots.

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