The Collaborative International Dictionary
Naperian
Napierian \Na*pie"ri*an\, Naperian \Na*pe"ri*an\,, a. Of, pertaining to, or discovered by, Napier, or Naper.
Naperian logarithms. See under Logarithms.
Usage examples of "naperian".
I calculated it, but I did it the easy way: Naperian logarithms and angles in radians, then converted back to degrees to show the relationship to kilometers on the ground.