Quote Originally Posted by Toolmaker51 View Post
...In daily use a nautical mile is rounded to 6000 feet for the best reason of all. It's fastest possible mental calculation of speed and distance, awfully handy when the course of vessels will cross or be head-on, to avert collisions. So plot of voyage could utilize correct distance to figure arrivals, and divert to 6000 if need arise....
If you divide 2*pi*3959*5280 (circumference of earth in feet) by 21600 arcmin, you get a value for a nautical mile of 6080... ft. The official value is 6076... ft.

Back in the day when I was helping to target ICBMs, we would occasionally encounter data expressed in nautical miles and had to convert it so the latter figure is burned into my brain. It's low on my list of things I wish I could forget but it's still there.

For TLAR purposes, a nice round 6000 is good enough.