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    Re: SOA vs SMG
    From: Irv Haworth
    Date: 2009 Nov 5, 10:03 -0800

    Hello Joe
    Good show and thanks for your input. Re small mistakes " don't sweat it" I
    recall a late friend of mine who held a commission in R Cdn Navy during WW2
    he was on a carrier (RN) and his job was to get the fighters back to the
    carrier after a sortie with the hun. One day he gave them the reciprocal of
    the course to return.. By the time he or ? realized the planes were overdue
    it was too late. The simple 180� mistake caused the loss of several airmen
    and planes.
    I will keep you informed..
    PS  You are correct the web site is sailwx.
    -----Original Message-----
    From: navlist@fer3.com [mailto:navlist@fer3.com] On Behalf
    Of joseph_schultz@rrv.net
    Sent: Thursday, November 05, 2009 3:00 AM
    To: NavList@fer3.com
    Subject: [NavList 10460] Re: SOA vs SMG
    Hi Irv,
    I think I get it.  Here's how the US Navy trained me, pertaining to surface
    SOA = speed of advance.  Labeled with letter "S" prefix on the dead
    reckoning (DR) track.  The planned speed through the water, ignoring
    anything that would affect the vessel, such as wind or current.
    SMG = speed made good.  Calculated from fix to fix, using the fix time
    interval divided into the distance between fixes.  The AVERAGE speed over
    ground, as the vessel can change direction and speed up or slow down at any
    point between fixes.
    SOG = speed over ground.  Considered an INSTANTANEOUS speed for a surface
    vessel, and was usually only used when planning a DR track.  Say, for
    example, the speed limit in a traffic separation scheme is 12 kts and we
    determine that we'll have a following current of 4 kts.  We'll then plan for
    a SOA of 12 - 4 = 8 kts in order to have a SOG of 12 kts.
    The Navy owned the ships so they had the final say in what the words were
    and what they meant.  "Your way, the right way or, if you like your pay, the
    Navy way."
    WMO runs their program so they have the final say as to what the words mean.
    Looks to me, from the US handbook that I refered to earlier, that WMO and US
    Navy agree on the definition of SMG.
    If I was a betting man (not more than a friendly cup of coffee) then I'd say
    that the web site you're referring to (sailwx.com ??) is downloading batch
    files from WMO, then doing a bit of computer processing before you see what
    you see.  They own their web site so they get to say what the words mean,
    regardless of the confusion they may create.
    As a department head on my second ship I had message release authority.  If
    I signed it then the radiomen sent it.  I signed for exactly one mistake in
    two years on that ship, a mistake small enough that I can't remember what it
    was.  But you'd think the sky had fallen - I remember that.  Your cruise
    ship made (and corrected) a small mistake in the scheme of things - don't
    sweat it.
    Keep us posted on your communications with these folks.  I like my coffee
    hot, black, and with a pinch of salt.
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