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    Silicon Sea: Leg 91
    From: Dan Hogan
    Date: 2004 Apr 15, 06:01 -0700
    Chart(s): Plotting Sheet, spchannel.jpg, NOAA 18022
     
    Dead-Reckoning problem     Leg 91  041504   Test your knowledge!
    ----------------------     ------  ------   --------------------
    Our last position A Running FIX(36d 27.4'N  126d 56.3'W) was on 17/09/2002
    {at} 02:11:20UT. The clouds have thickened and a fog is building. We have traveled
    310.5 Nmi since the RFIX Position.
     
    TC 112.1d, Speed 10.0 Kts.
     
    We are headed for MOP4(34d 20.0'N  120d 33.0'W) at the entrance to the Santa
    Barbara Channel in Southern California.
     

    1)  What is the DR position at the end of the 310.5 Nmi run?
    --  --------------------------------------------------------
     
    2)  What is the Zone Time at the DR position?
    --  -----------------------------------------
     
    3)  From the DR position, what is the TC and distance to MOP4(34d 20.0'N
        120d 33.0'W)?
    --  -------------------------------------------------------------------------
     
    Sailing in a thick fog we anxiously wait for dawn. At 12:14:20UT {at} 18/09/2002 we
    sight a lighted bouy, FL(4)Y 20s PA. The chart lists it as an "ODAS" bouy. A
    weather bouy. In the fog we here the fog horns of ships in the Santa Barbara
    Channel Ship Traffic Lane.
     
    As the light brightens we see an Island about 2 points off the starboard bow.
    Checking chart NOAA 18022 we determine that we are looking at San Miguel Island.
     
    With the fog and heavy ship traffic in the channel we elect not to enter the
    channel. We will go outside of the Santa Barbara Channel Islands. So we alter our
    course to due South.  So as to pass well clear of Richardson Rock laying NW of
    the West end of San Miguel Island.
     
    At 04:20:10ZT we are 5.6 miles West, abeam of Richardson Rock
    (34d 01.2'N 120d 06.2'W). We set a course for (33d 45.0'N 120d 00.0'W),
    we call it MOP5.
     
    Speed 10 Kts, Var 13dE, Dev 2.5dW. Current Set 145d, Drift 0.2 Kts.
     
    4)  What is the Compass Course/Course-to-Steer?
    --  ------------------------------------------
     
    From MOP5 we plot a course to the Pt. Fermin Light which is located on the
    prominent heights above San Pedro Harbor.
     
    Speed 9.5 Kts, Dev 13dE, Var 2.0dW, Current Drift 0.2 Kts, Set 180.0d.
     
    5)  What is the TC and Distance to Pt. Fermin(33d 42.3'N  118d 17.5'W) from
        MOP5(33d 45.0'N  120d 00.0'W)
       
        What is the Compass Course/Course-to-Steer(CC)?
    --  -----------------------------------------------------------------------
     
    6)  What is our Estimated Time of Arrival(ETA), in Zone Time, at MOP5?
    --  ------------------------------------------------------------------
     

    7)  In Zone Time(ZT), what is our Estimated Time of Arrival(ETA) and Date at
        Pt. Fermin? To the nearest minute is adequate for picky Navigators.   
    --  ------------------------------------------------------------------------
     
    NOTE:
    Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction
    -2.5', Time hh:mm:ss in UT,unless otherwise stated. Silicon
    Sea II is a 34,000 lb(15.40t) displacement sailing vessel, 48' 3"
    (14.70m) LOA. 39' (12.00m) LWL; Cutter rigged. Can tack to 45d.
    Water Tanks = 220 gal(1000 ltrs). Fuel Tanks = 155 gal(700 ltrs).
    Fuel consumption .675 gal/Hr at 8.5 Kts. DR(Ded-Reckoning)=position
    by sailings, EP(Estimated Position)=DR+current affect. Dist to
    Horizon: Nmi = SQRT HE{at}mtrs x 2.07; Nmi = SQRT HE{at}ft x 1.17.
     
    PLEASE respond with your results and thinking on these exercises to
    the NAVIGATION list at large. If you have questions or problems, A
    lot of folks on the list are knowledgeable and willing to help. Any
    questions or doubtful areas will be responded to promptly. Let us
    hear from you soon!
     
    Good Navigating!
     
       -=The Navigation List Working Group=-
     
            Peter Smith -  Smith_Peter{at}emc.com
            Federico  Rossi - fedeastro.rossi{at}libero.it
            Dan Hogan - dhhogan1---.net
       
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