Aerial mileage, also known as nautical miles, differ from ground mileage calculations in that nautical miles account for the curvature of degrees as measured in sea charts. Ground miles only measure direct distance through an imaginary straight line.
Nautical miles are measured as 6,076 feet, which is almost exactly equal to 1 minute of latitude on a sea chart. It is difficult to use ground miles, which are measured as 5,280 feet, while calculating potential distance over sea or air because sea travel maps have used the Mercator projection method for navigation for hundreds of years. This system was developed to allow travel over long sea distances as straight course lines instead of curved ones that overcompensate for the natural curvature of the planet.
As the nautical mile is equivalent to 1 minute of latitude, it makes calculating distance with a sea map a simple procedure that does not require any calculations. To convert between nautical miles and land miles, multiply the nautical mile distance by 1.15. Conversely, land miles can be converted to nautical miles by multiplying the land mile distance by 0.868.
Due to the difference in nautical and ground miles, each measurement has its own calculation for speed as well.