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I had a quick perusal through successive issues of Bowditch, starting from
1926 and working my way foward through time. It was not until I reached the
1966 reprint of the 1962 edition, that I found an abbreviation listed on
page 65, as follows: "mi., M".

On page 986 of the same edition, under chart symbols, the abbreviation is
given as: "M".

The 1984, two-volume Bowditch provides the same abbreviation on page 63,
volume 1. On page 1163 of the same publication under Appendix A:
Abbreviations, it is listed as "NM" and "n. mi".

Moving on to Dutton's (14th edition) Section A, page 3 (at the end of the
textbook) provides several possibilities: "M" "Mi" "NMI" & "NM".

The 12th edition of Dutton's indicates that it is simply "M".

In the 1955 edition, Volume 1 of the Admiralty Manual of Navigation
indicates that: "...Except on charts where the symbol M is now adopted, the
unit is always denoted by a ', which is also the symbol for a minute of
arc".

British Publication, AP 1234, Air Navigation (Air Ministry, 1944) gives it
as "n.m."

By the look of it, you can take your pick. I find it rather odd that such an
important unit of measure would not have a clearly unique and
universally-accepted symbol. It is a real mixed bag.

I generally use "nm" or "NM", depending on my mood that day.

cheers,

Robert

----- Original Message -----
From: "John Kabel" 
To: 
Sent: Tuesday, June 07, 2005 10:58 AM
Subject: Abbreviation of Nautical Mile


> 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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