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    Re: Silicon Sea: Leg 81
    From: Bill Noyce
    Date: 2001 Oct 19, 3:22 PM

    > At 14:00:00UT @ 08/07/2001, by log meter, we have traveled a distance
    > 439.5 Nmi since our last DR position. True Course(TC) 289.9d.
    > 1)  What is the current DR position?
    > --  --------------------------------
    By Mercator sailing:  10d 19.8' N, 128d 34.8' W
    (Mid-lat gives                     128d 38.1' W)
    > 2)  What is the approximate distance and direction to the storm
    >     (019d 45.0'W  120d 30.0'N) from our DR position at 14:00:00UT @
    >     08/07/2001?
    > --  ----------------------------------------------------------------
    How approximate is "approximate"?
    dLat = 9d 25', dLon = 8d 5'
    9*9 + 8*8 = 145 ==> storm is about 60*12 = 720 miles away,
    somewhat north of northeast.  I assume this is enough info
    to estimate the storm's effect on us...
    More carefully,
    Mercator:     760.0 nmi, 039.6d
    Great Circle: 733.6 nmi, 038.7d
    > 3)  What is the DR position at the end of this time?
    > --  ------------------------------------------------
      TC    Dist    Lat          Lon
                  10d 19.8 N  128d 34.8 W
    289.9d  57.0  10d 39.2 N  129d 29.3 W
    278.0d  74.4  10d 49.6 N  130d 44.3 W
    275.0d  24.75 10d 51.7 N  131d  9.4 W
    270.0d  46.8  10d 51.7 N  131d 57.0 W
    > 4)  What is the UT/GMT date and Time?
    >     What is the Zone Time(ZT) and day?
    > --  ----------------------------------
    Time adds up to 2 days 11.5 hours.
    Time is 11 July 01:30 UT, zone is 9 hrs west,
            10 July 16:30 ZT
    > 5)  What is the TC & Distance from the DR to our Hawaii landfall point
    >     (19d 30.0'N  154d 45.0'W)
    > --
    by Mercator (Meridional Parts):
    From  Lat= 10d 51.7 N  MP=  651.4  Lon= 131d 57 W
    To    Lat= 19d 30.0 N  MP= 1185.8  Lon= 154d 45 W
          dLat    518.3'   dMP  534.4  dLon 1368'
    TC = atan(1368/534) = N 68.7d W = 291.3d
    Dist = 518.3/cos(68.7) =         1424.7 nmi
    > 6)  What is the unknown body?
    > --  -------------------------
    > 7)  What is the FIX position at the time of the unknown body?
    > --  ---------------------------------------------------------
    DR position at 03:40 was about 11d N, 132d 20' W.
    The FIX draws out to about 11d 33' N, 132d 25' W.
    I'm not very happy with my work on this fix.  I originally had
    the wrong DR, and all my intercepts were over 60 miles long.
    But at least Antares and Mars, with nearly the same azimuth,
    also had nearly the same intercept.  (I remember showing the
    Cub Scouts at camp last July how the Red Planet was right next
    to the Red Star -- at least I thought it was cool!).  Found
    the error in the DR, and recalculated the sights from there
    -- but now my Antares and Mars lines are nearly 5 miles apart
    and still nearly parallel.
            Antares    Mars
    GHA   98d 17.3     90d  1.2
    dec   26d 26.2 S   26d 51.1 S
    LHA   34d  2.7 E   42d 18.8 E
    K     30d 57.8 S   34d 23.6 S
    Hc    40d  2.7     34d  9.6
    Ho    39d 33.3     33d 44.2
    Int       29.4 A       25.3 A
    Z        139.1d       133.5d
    I've checked it by hand -- time to ask the computer where I
    screwed up, I guess.
            -- Bill

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