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    Re: Smart and Shearme Position Line Tables
    From: David Pike
    Date: 2020 May 7, 01:43 -0700

    DavidC you asked:  ......... what was the purpose of the AMN?

    I’m primarily an air navigator, so I’ve no flag to fly for the ANM.  If it were AP1234, it would be different.  I just happen to have the 1938 ANM taking up space on my bookshelf.  I hadn’t opened it more than a couple of times in 20 years before this week.  The point I was trying to make is that each edition is a product of its age, even if it’s just the addition of a glossy picture to the front.  Therefore, unless the study is ‘The development of manuals over the years’, any comparison of different manuals separated by a war or several decades of peace needs to be undertaken with caution.  Also, you need to read each edition in the spirit of its age.  I.e. in the case of ANM 1938, you need your 1938 (pre digital calculator) hat on, and some might say, a PhD in Royal Naval History.  E.g. on page 126 of Vol2, does ‘hav(PX tilde PZ) = hav (lat. tilde dec.)’ mean ‘PX when it’s approximately equal to PZ’ as Google 2020 suggests, or does it simply mean ‘PX or PZ’?

    Actually, the solution of the PZX triangle in Vol2 from page 125 seems to be done as well an any textbook of the period, especially when you realise they’ve already covered much of the maths while discussing great circle problems on the Earth in Chap IV.

    I need to put this to bed now, because I’ve got to get tuned in again to another little project I’ve got myself involved in.  DaveP  

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