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    Re: Silicon Sea: Leg 74
    From: Michael Wescott
    Date: 2001 Jun 16, 17:01 EDT

    > Our last Running FIX(13d 37.8'N  68d 10.5'W) 16:30:29UT {at}XXX.XXX
    > We were headed for Aruba Gap(13d 50.0'N  70d 00.0'W).
    > On 02/06/2001 {at}XXX.XXX7 Nmi from our RFIX we made a course
    > change at the Aruba Gap (13d 50.0'N 70d 00.0'W) waypoint. Our destination is
    > Cristobal, Panama(09d 23.0'N 79d 55.0'W). We are anticipating a transit of the
    > Panama Canal.
    > Var 8.0dW, Dev 1.0dE . Current Set 275.0d Drift 1.5 Kts. Speed 10.4Kts.
    > 1) What is the the TC and Distance from Aruba Gap(13d 50.0'N 70d 00.0'W)
    >    to Cristobal, Panama(09d 23.0'N 79d 55.0'W)?
    > -- ---------------------------------------------------------------------
    dLat = 9d23.0' - 13d50.0' = -4d27.0' = -267.0
    dLo  = -(79d55.0 - 70d00.0') = -9d55.0' = -595'
    dep = -595 * cos 12 = 582.0
    TC = 270.0 - atan(267/582) = 245.4
    > 2)  What is the Compass Course(CC)/Course-to-Steer?
    > --  -----------------------------------------------
    CC = 245.4 + 8.0 - 1.0 = 252.4
    Correcting for current (on plotting sheet) gives
    course 242.5T or 249.5C
    > Since our turn at Aruba Gap(13d 50.0'N  70d 00.0'W)We have been sailing in a
    > steady wind and clear skys.
    > At 05:16:28ZT {at}XXX.XXX
    > Speed 10.4 Kts, TC 245.5d.
    > 3)  What is the 05:16:28ZT DR position?
    > --  -----------------------------------
    We're in the GMT-5 zone centered at 75d W
     04-06-2001  10:16:28UT
    -02-06-2001  06:46:28UT
     ======================
      2 days     03:30:00  = 51.5 hr
    D =  51.5 * 10.4 = 535.6
    dLat = 535.6 * cos 245.5 = -222.1 = -3d42.1'
    Lat = 13d 50.0'N - 3d 42.1' = 10d 07.9'N
    dep =  535.6 * sin 245.5 = -487.4
    dLo = -487.4/cos 12 = 498.3' = -8d 18.3'
    Lon = 70d 00.0'W + 8d 18.3' = 78d 18.3'W
    DR: 10d 07.9'N   78d 18.3'W
    > We take the following sights:
    >     Body            UT/GMT          Hs
    >     Fomalhaut       10:17:22        47d 14.7'
    >     Deneb           10:17:56        51d 52.0'
    >     Altair          10:18:00        59d 18.2'
    Wow! only 4 seconds between sights. :-)
    >     Vega            10:18:46        37d 34.3'
    >     Venus           10:19:33        33d 20.0'
    > 4)  What is the position FIX?
    > --  -------------------------
    Using NAO sight reduction table and plotting sheet
    about
    10d 29.0 N   78d 30.5W
    > Speed 10.0 Kts. Var 5dW, Dev 1.5dE. Current Set 100.0d Drift 0.7 Kts.
    > 5)  What is the TC and Distance to Cristobal(09d 23.0'N 79d 55.0'W)
    >     from the FIX position?
    > --  ----------------------------------------------------------------
    Using plotting sheet  TC = 232  D = 106
    > 6)  What is the ZT and Date of our ETA at the Cristobal waypoint
    >     (09d 23.0'N  079d 55.0'W)?
    > --  ------------------------------------------------------------
    Allowing for current, SOG is about 9.5 which is about
    11:03 sailing time. That's 21:21 UT or 16:21 ZT same day
    4-Jun-2001
    <PRE>
    --
            Mike Wescott
            Wescott_Mike{at}XXX.XXX
    </PRE>
    

       
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