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    Re: SOA vs Positions
    From: George Huxtable
    Date: 2009 Nov 12, 23:11 -0000

    Thank you for clarifying, Irvin.
    
    Yes, that ship-speed did look high, but then some surface vessels can travel 
    at that speed, so it wasn't, on the face of it, impossible without a bit of 
    additional information, which you have just provided.
    
    Most likely, they have recorded the time of one of those observations wrong, 
    so it covers a 2-hour interval rather than 1 hour. It provides duff data 
    that nobody looks at, at the sending end. Very spapdash, but typical of the 
    careless way such automated stuff gets handled.
    
    Yours, George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message ----- 
    From: "Irv Haworth" 
    To: "Navlist" 
    Sent: Thursday, November 12, 2009 7:52 PM
    Subject: [NavList 10598] Re: SOA vs Positions
    
    
    
    
    
    George H
    Sorry for delay in getting back to you (had wireless problem with router).
    
    I will not annoy the other members by re-hashing my past posts on ships
    sending WX data to WMO who appear to be using wrong term (S.O.A. ) and
    algorithm to calc same, run (Dist)-and/or time SOA  given reported
    positions.
    In this case, given the reported positions, the correct Dist. is indeed
    34.8. NM which they reported as 35 NM but S.O.A. is ( correctly  ?) given as
    34.8. So far so good..more or less.. except the run time is 1 hour and this
    cruise ship cannot attain such a speed. In earlier posts the "system"(as I
    have already noted) reported SOA's of over 500 kts and as high as 900
    kts.(Calc based on wrong hemisphere (� W instead of E).(How is � and �
    determined/reviewed ?)
    I am simply trying to determine  who or what is checking the data ...the
    navigator/ algorithm used or WMO ....if anybody.
    I have brought this matter to the attention of a US Gov chap who seems to be
    involved with some of these issues and while  he did not have the answers
    ,will look into the issue and ,hopefully, advise after the 14 Nov Anno
    Domini 2009.
    Perhaps I should note here that my keen interest in these matters is that
    this is not hypothetical data(or supposed to be) , but is put out in real
    time as an additional input to WX forecasting on high seas, by W.M.O
    (metrological). (Garbage in garbage out appears to still be a problem ).
    
    Perhaps I should use the non de plume "fido" as one with the bone.  Hi...hi
    Aka -Irvin
    
    -----Original Message-----
    From: navlist@fer3.com [mailto:navlist@fer3.com] On Behalf
    Of George Huxtable
    Sent: November-08-09 4:52 PM
    To: navlist@fer3.com
    Subject: [NavList 10509] Re: SOA vs Positions
    
    
    I agree with the calculation of 34.8 miles as the distance between the two
    given positions. What's the problem?
    
    George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message ----- 
    From: "Irv Haworth" 
    To: "Navlist" 
    Sent: Sunday, November 08, 2009 11:59 PM
    Subject: [NavList 10508] SOA vs Positions
    
    
    
    Does
    
    The plot thicken ?
    
    Dist.
    
    from
    
    11AM/12.00
    
    Is 34.8NM
    
    Which
    
    =34.8
    
    Seems to indicate positions are in error ?
    
    
    
    
    
    
    
    
    
    Notes
    
    date/time
    
    lat
    
    lon
    
    naut. miles run
    
    SOA
    
    wind from
    
    knots
    
    barom.
    
    wave height
    
    air temp
    
    dew point
    
    water temp
    
    
    2009-Nov-08 16:00
    
    S 44�24'
    
    E 167�00'
    
    43
    
    10.7
    
    220
    
    27
    
    1016.3
    
    1.5
    
    12.0
    
    10.2
    
    13.0
    
    
    2009-Nov-08 12:00
    
    S 44�24'
    
    E 166�00'
    
    35
    
    34.8
    
    220
    
    15
    
    1019.3
    
    0.5
    
    12.0
    
    
    
    2009-Nov-08 11:00
    
    S 44�18'
    
    E 165�12'
    
    290
    
    15.2
    
    250
    
    21
    
    1022.2
    
    13.0
    
    12.7
    
    13.0
    
    
    
    Please excuse my lead-in.it now appears the algorithm used must
    automatically calc. SOA based on Rhumb dist. In this case dist is 34.8 (my
    RL calc) and not 35 NM as NM  Run.
    
    What I am trying to determine : are data generated/reported automatically
    from a GPS  without any inputs from navigator, as well as SOA issue.
    
    ( I have been following the track of a large cruise ship across S. Pacific
    and now wondering what or who does what.with confidence. Reminds me of a
    quip in poor taste "if you drive then drink and face the traffic with
    confidence").
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
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