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Chart(s): Plotting Sheet, spchannel.jpg, NOAA 18022
Dead-Reckoning problem Leg 91 050104 Test your knowledge!
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Our last position A Running FIX(36d 27.4'N 126d 56.3'W) was on 17/09/2002
@ 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?
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2) What is the Zone Time at the DR position?
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3) From the DR position, what is the TC and distance to MOP4(34d 20.0'N
120d 33.0'W)?
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Sailing in a thick fog we anxiously wait for dawn. At 12:14:20UT @
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?
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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)?
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6) What is our Estimated Time of Arrival(ETA), in Zone Time, at MOP5?
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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.
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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 -
Federico Rossi -
Dan Hogan -
