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    Re: Titanic's last stars
    From: Geoff Hitchcox
    Date: 2019 May 5, 05:21 -0700

    Gentlemen, I must apologise for some faulty logic in my last message. [1]

    I had determined there was a (00:01:18") inherent error by using a "flat earth" Traverse Table. I subtracted this value from the Titanic SOS coordinates (by Samuel Halpern [2] ) which resulted in a very good agreement between this new location and using Rhumb Maths.

    On reflection about using that logic - I realised I should *not* have done this. If going one way (Fix->Iceberg) then yes this (00:01:18") error is going West too far. However if one goes Fix->Iceberg and then Iceberg->Fix (which effectively is what Samuel Halpern is doing) then the (00:01:18") error cancels out - you end up exactly where you started from, using the same set of Traverse Tables!

    So Titanic's last CN fix coordinate delta, that I derived in my very first post on the topic - is still 1.40 NM (for the spheroid model). [3]

    However now that we are this far, let's finish off with also using the WGS84 model of the shape of the world - to calculate Titanics probable C.N. Fix error.

    Summary:
    41:45:30" N, 49:55:00" W = GPS referenced Iceberg allision [4]
    41:52:30" N, 47:54:00" W = Sam's Titanic Fix at (22:28 GMT) [2]
    41:51:54" N, 47:52:37" W = Geoff's (WGS84) location for Titanic fix [5]
    41:51:54" N, 47:52:18" W = Geoff's (Sphere)  location for Titanic fix [6]

    Geoff's error calculation, of final Titanic Celestial Fix (14 Apr 1912)

    1.19 NM from Geoff's Rhumb calculation of fix (using WGS84).
    1.40 NM from Geoff's Rhumb calculation of fix (using Sphere).

    Based on GPS reference of Iceberg and (repaired) Titanic SOS position.

    Linking, through the application of Rhumb Maths.

    Titanic knew where she was - at the last Celestial Navigation fix !

    There is still controversy over exact numbers of RPM, speed, direction, times of fix and allision with Iceberg. However to me the overall geometry of Iceberg and Celestial Fix remains - but the *exact* numbers may never be known!

    Although this was an enjoyable exercise for me, I actually did very little. It was Samuel Halpern who did all the heavy lifting of the research so far - I just had a novel idea and plugged some numbers into online calculators !

    Regards, Geoff Hitchcox, Christchurch, New Zealand.   6 May 2019
    ------------------------------------------
    [1] Previous Message:
    http://fer3.com/arc/m2.aspx/Titanics-last-stars-Hitchcox-may-2019-g44881

    [2] Mistakes In The Night , By Samuel W. Halpern
    www.titanicology.com/Titanica/Mistakes.pdf

    [3] First msg, with LOP's and USNO data
    http://fer3.com/arc/m2.aspx/Titanics-last-stars-Hitchcox-apr-2019-g44856

    [4] Collision Point by Samuel Halpern, July 2007
    http://www.glts.org/articles/halpern/collision_point.html

    [5] WGS84 Rhumb Calculator
    http://www.edwilliams.org/msail_mod.html

    [6] Spheroid Rhumb Calculator
    http://www.movable-type.co.uk/scripts/latlong-nomodule.html

       
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