Gregory's Server@mhoye Nifty. As they're pretty close to 0.6/1.6, I just add a half and a tenth to go km -> mi, and add that to the original value to go the other way mi -> km. Some prefer to divide by 5 then multiply by 3 (same 0.6 ratio) but I find 2 simple additions to be easier (for my brain).
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~1.8... from the top of my head. You're supposed to fit a whole number of nautical miles into a section of a great circle, measured in degrees and seconds.  @hlangeveld And this has to be on the equator if were talking about driving from longitude to longitude. And then a nm is a minute on the circle. 1.8 seems right, had to look the 1.852 up as well. Bonus for me: It seems I finally got the latitude/longitude thing right. ("all longitudes are equally long" helps me out) ;-) @hlangeveld @jesterchen I wrote this yesterday and deleted it coz I felt I've hijacked the OP. But for completeness... Equator to pole is very close to 10,000km (it was defined as that but an error crept in). Similarly, a nautical mile is one minute of (latitudinal?) arc, so 90 degrees x 60 mins = 5,400 nm. Again errors occurred. So km -> nm is roughly 0.55 (11/20ths), so the reverse is approximately 20/11 (~1.818...), which is close to (2-0.2) for easy calcs. |
@0xThylacine Yep, my way exactly. And for some reason when we talked about miles at school, the number 1.609344 got burned into my head. Though I can't seem to remember the value for nautical miles...