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John:

USPS courses (especially the two new coastal piloting courses with which
I'm most familiar) use "nm"   But as an electrical engineer, I am
constantly involved with new computer chips whose transistor sizes are
measured in "nm's," where "nm" is used in its correct ISO definition,
nanometer (billionth of a meter).

I was involved in providing early feedback on these courses and the "nm"
abbreviation bugged me.  I tried several sources and was unsuccessful in
finding an official abbreviation for nautical mile.  (And you're right
about there being no consistency in Chart 1).

I for one would at least favor NM so there is less confusion with nanometer.

(I will agree with others who have answered your question that there's
little chance of confusion, though -- The distance between transistors
and the distance between ports may both be expressed by a number
followed by "nm" and I doubt one unit will be confused with the other.
It's just that the purist in me would prefer an unambiguous abbreviation.)

Lu Abel

John Kabel wrote:
> An interesting question came up the other day as we were editing a course
> on Electronic Charting.  What is the accepted abbreviation of "nautical
> mile"?  We need a standard that can be applied across all Canadian Power
> and Sail Squadron courses.
>
> I did some searching and came up with the following, to start the
> discussion:
>
> - Bureau International des Poids et Mesures notes that there is no accepted
> symbol, though all agree on the distance measured (1852 metres)
> - neither the Canadian Metric Practice Guide nor the CSA publication
> International System of Units have an abbreviation in their tables
> - Wikipedia (the online encyclopedia) suggests that "nm" is preferred,
> especially in aeronautics
> - Canadian Hydrographic Service uses "M" in its Abbreviations
> - The NOAA Chart 1 (Abbreviations) lists all of "M", "Mi", "NM" and "N M"
> for "nautical mile(s)"
> - Nav Canada, the agency responsible for air traffic control in Canada,
> uses "NM"
> - Bowditch (1995) gives both "n.mi." and "NM" in Abbreviations and Acronyms
>
> So, what does the group think?  What is USPS usage?  What is Navy usage?
> Please reply either to the list or to me privately.
>
> Thanks.
>
> John Kabel
> London, Ontario
>
>
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