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Sight Reduction and                           Re-Issue
Dead-Reckoning problem     Leg 89  050504     Test your knowledge!
---------------------------    -------  ---------    ----------------------

On 11/09/2002 at 05:10:21UT we had a Running FIX(RFIX) (39d 43.5'N  151d
59.1'W).

Due to movement of the Pacific High. With the resulting wind change we have
altered our course toward Mid-Ocean Point 3(MOP3) at (37d 00.0'N  130d
00.0'W).

Var 17dE, Dev 2.0dW. Current Drift 0.4 Kts, Set 145d. Speed 10.3 Kts.

1)  What is the TC and Distance to MOP3(37d 00.0'N  130d 00.0'N)?
--  ------------------------------------------------------------

2)  What is the Compass Course(CC)/Course-to-Steer to MOP3?
--  -------------------------------------------------------

Due to overcast sky and intermittent rain we are unable to get a FIX for 3
days
until a Log reading of 724.4 Nmi since the Running FIX(RFIX) on 11/09/2002.
At
05:10:21UT (39d 43.5'N  151d 59.1'W).

    Var 17dE, Dev 2.0dW. Speed 10.3 Kts, Set 175.0d, Drift 0.4 Kts

3)   What is the Dead Reckoning(DR) position for the Sight Reduction?
     Use the time of the first SR.
--   ----------------------------------------------------------------
Then we manage to get the following round of morning sights on UT
15/09/2002:

 UT    Body   Hs
 03:30:31        Moon LL   25d 59.3'
 03:31:00  Polaris   36d 40.2'
    03:31:12  Vega   83d 07.8'
 03:31:21  Deneb         59d 28.3'
 03:31:55  Altair   52d 57.0'
 03:32:55  Antares   22d 51.9'

Almanac Data

03:30:31  Moon       GHA = 126d 29.5' Dec = 25d 23.2'S
03:31:00  Polaris  GHA = 007d 46.3' Dec = 89d 16.5'N
03:31:12  Vega   GHA = 127d 28.3' Dec = 38d 47.4'N
 03:31:21  Deneb   GHA = 096d 22.9' Dec = 15d 17.5'N
 03:31:55  Altair  GHA = 109d 10.8' Dec = 08d 52.5'N
 03:32:15  Antares  GHA = 159d 46.3' Dec = 26d 26.3'S

4)   What is the FIX position?
--   -------------------------

Examining our charts at the time of the FIX, we select a MOP4 off of Point
Conception, California near the entrance to the Santa Barbara Channel at
(34d 20.0'N 120d 33.0'W).

Speed 10.0 Kts. Current Drift 0.6 Kts, Set 170d. Var 15dE, Dev 2.0dW.

5)  What is the Compass Course(CC)/Course-to-Steer?
--  -----------------------------------------------

Speed 10.0 Kts. Current Drift 0.6 Kts, Set 170d. Var 15dE, Dev 2.0dW.

6)  What is our Estimated Time of Arrival(ETA), Time and Date at MOP4 near
the
    Santa Barbara Channel MOP4 (34d 20.0'N  120d 33.0'W), UT & ZT?
--
---------------------------------------------------------------------------

As we completed plotting our FIX position, the weather picks up and the
cloud
cover increases again. We also run into contrary winds,rain and swells that
are
heading our course.

Var 15dE, Dev 2.0dW.

We make the following traverses against the wind.

 Compass Course   Distance

 86.6d     45 Nmi
 45.0d     55 Nmi
 80.0d     75 Nmi

7)  What is the DR position at the end of the last Tack?
--  ----------------------------------------------------

8)  What is the TC and Distance to the entrance to the Santa Barbara Channel
    waypoint(34d 20.0'N  120d 33.0'W) from the last DR position?
--  ------------------------------------------------------------------------

NOTE:
Lat & Lo = XXd XX.X', Date=DD/MM/YYYY, 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@mtrs x 2.07; Nmi = SQRT HE@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@emc.com
        Federico  Rossi - fedeastro.rossi@libero.it
        Dan Hogan - dhhogan1@earthlink.net

   

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