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    Re: Smart and Shearme Position Line Tables
    From: David Pike
    Date: 2020 May 5, 03:25 -0700

    DavidC you wrote:  The Admiralty was subsumed into the Ministry of Defence in 1964. When I  mention the AMN I am thinking of volumes issued between 1914 and 1964. The earliest copy I have is 1922 volume 2., the latest are 1964 vols 1 and 2. In between I have various copies of vol1, vol2 and vol3. I did find a copy of the original 1914 edition but was too slow to buy it.

    Although the Admiralty was subsumed into the Ministry of Defence in 1964, the name didn’t disappear altogether.  You can still buy Admiralty Charts although the UK Hydrographic Office is largely civilianised, and you can still buy the Admiralty Navigation Manual (ANM), if you have about £300 to spare, which is still authored by the Royal Navy, but is produced by the Nautical Institute.

    I don’t pretend to be an expert on the ANM; I just happened to have my father’s Vol 1 and 3 of the 1938 edition on my bookshelf plus Vol 2, which I bought from Abe Books.  The point I was trying to make is that editions change, sometimes slowly while they’re authored by older professionals steeped in their younger life techniques and traditions, but occasionally more quickly when there becomes need for step change. 

    A typical example is the RAF Navigators Manual AP1234/3456.  One step change occurred at the start of WW2.  I’ve not seen a copy, but prior to that, the manual was produced for career RAF Pilots who’d chosen to specialise in navigation, and its style must have been similar to the 1938 ALM.  In WW2, with the need to train thousands of bright young chaps straight off the street to be Navigators, it was realised that a much simpler, straight to point manual was required with no unnecessarily clever maths.  The result was the 1941 edition written by a Pilot Navigation Expert Sqn Ldr, later Group Captain, Dickie Richardson.  By the end of WW2, new equipment was being introduced so quickly that there was a need to go to a loose leafed production in constant need of amendment.  Then, a few decades later, as the RAF contracted and most Non-Pilot Aircrew training was concentrated a single unit, almost all the Non-Pilot Aircrew Manuals were concentrated into a single manual with many Volumes, AP3456.  I won’t go on, but eventually, the need to defray costs by commercialisation comes in with flashy front covers updated regularly as presentational tastes change.

    you also wrote:  To give you an example of my problem -  I am researching the formulae for calculating azimuth. Over the years I have become confused with the various versions. If I go to Bowditch 1958 and 1995 I can find the formulae. There are three of them, depending on the input arguments -  d t l,  d h l, and d h t. Presumably there is a formula for h l t but I have not found it.

    Current Bowditch is very readable, as is/was AP1234/3456.  Not willing to dish out £300, I’ve not looked at later editions of ANM.  One thing I do note however is that you say the 1995 and 1958 editions of Bowditch contained three formulae for Azimuth.  I’ve not been able to see them, but later editions only contain two, co-lat, co-alt, and co-dec, which is a side, side, side problem, and co-lat, hour angle, and co-dec, which is a side, angle, side problem.  Left out is co-alt, co-dec, and hour angle, which like co-alt, co-lat, and hour angle is a side, side, angle problem, and a bit more complicated to solve.  Will you send the 1958 Bowditch formula for co-alt, co-dec, and hour angle, because it should provide a clue to a co-alt, co-lat, hour angle formula you were looking for?  DaveP

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