

Sight Reduction and 
Dead-Reckoning problem     Leg 18  091096*   Test your knowledge!
----------------------     ------  ------   --------------------
On 02/06/96 @ 13-30-00 GMT our DR was 35d 40.5'N  15d 25.2'E. We
have been maintaining a TC of 106.9 and a speed of 8.6. It
>is now 18-10-00 GMT. Var 0.0d E, Dev 4d E.

1)  What is the 18-10-GMT DR position?
--  ---------------------------------

2)  Based on this DR, what is the Zone Time(ZT) of the End of Civil
    Twlight?
--  ---------------------------------------------------------------

We run an estimate of our dist traveled to the End of Civil
Twlight it is 3.7 mi. Being cautious we use that DR for our SR.

3)  What is the DR we use for our sight reductions?
--  -----------------------------------------------

We take the following sights:

     GMT        Body        Hs            Zn
     
     18-25-49   Vega       18d 00.3'      54.7
     18-29-10   Spica      40d 58.8'      158.7
     18-35-12   Procyon    17d 59.3'      263.5
     
4)  What is the FIX position? Use 18-25-49 GMT for plotting.
--  --------------------------------------------------------

Compare the DR for Question 3) with the FIX of Question 4).

5)  Is there a sufficient differance in them to consider
    taking action?

    What would you do?
--  ----------------------------------------------------

6)  What is the SMG and CC from our Departure Position at
|    (35d 53.5'N  14d 35.0'E) to our current FIX? TC 107.7,
|   Speed 8.6 Kts, Drift 0.4 set 125.0d.
--  -----------------------------------------------------

7)  What is the Dist we have traveled from our Departure
    Position to the FIX? 
--  -----------------------------------------------------

8)  Assuming our SMG remains the same, what is our estimated
    position if SunRise(SR) is at 03/06/96 @ 03-41-00 GMT.
|   TC 107.7
--  --------------------------------------------------------

Note:
Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 8 Feet, Index correction -.2', Time
hh-mm-ss in UTC/GMT. Silicon Sea is a medium displacement sailing vessel, 40
Feet LOA. 38 Feet LWL; Cutter rigged. Looks a lot like a Mason. Can tack to
45d. 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 Navgation List Working Group=-

        Peter Smith  - psmith@wellspring.us.dg.com
        Ron Legere   - ronald.legere@yale.edu
        Tony Severdia- anthonys@ix.netcom.com
        Dan Hogan    - dhhogan@lightside.com
        Wes Murfin   - cn1907@coastalnet.com (Cartographer)


