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On 9 Apr 2001, at 15:55, Yves Arrouye wrote:
> Hi,
>
> Here's my navigation. I have to thank Ed Falk for his sample leg
> (http://www.best.com/~falconer/Navigation/) which was a great help (the
> plotting sheets were nice, especially since my local West Marine didn't
> carry the real ones). I used as much of the online government calculators
> I could find, and included links to them. They're really nice. I'll do
> other legs using paper after I get the books :)
>
> > Chart(s): Plotting Sheet
> >
> > Dead-Reckoning problem     Leg 69  040401   Test your knowledge!
> > ----------------------     ------  ------   --------------------
> >
> > The last DR position was(10d 27.9'N  52d 26.4'W) on 18/05/2000 @
> > 12:30:01UT.
> > Our Speed has been 10.7 Kts, TC 288.9d Var 19dW. Dev 1.5dE.
> > Current Set
> > 285d
> > Drift 0.5Kts.
>
> Using a transverse table (http://pollux.nss.nima.mil/calc/traverse.html),
> we use:
>
> Course angle: 288d 54'
> Distance: 107 (10.7 * 10 hours, which includes an approximation for the
> current)
>
> and we find:
>
> Difference of latitude: 0d 34.66'
> Departure:                 101.23
>
> which gives us:
>
> Difference of longitude: 1d 43.1' (102.23 * cos 11)
>
> Our DR position is:
>
>      1  11               1
>     10d 27.9'N          52d 26.4'W
>   +     34.7'         +  1d 43.1'
>     ----------          ----------
>     11d 02.6'N          54d 09.5'W
>
> We'll use an AP of 11d 00.0'N and 54d 00.0'W.
>
> > On that evening we take the following sights:
> >
> >         Body            UT                                     Hs
> >
> >         Sirius      22:15:30                    28d 16.3'
> >         Spica           22:17:02            42d 20.6'
> >         Avior           22:19:00            15d 55.3'
> >         Bellatrix       22:19:45            13d 26.5
> >         Dubhe           22:20:12            37d 56.1'
> >
> >
> > 1)  What is our FIX position?
> > --  -------------------------
>
> Instead of a paper Almanac, I used the celestial navigation data from the
> U.S. Naval Observatory at http://aa.usno.navy.mil/ (then click on Data
> Service and then click on Celestial Navigation Data). This page gave me Hc
> and Zn directly, which I feel is cheating. Is there a page there that
> would give me just the almanac data?
>
> Star:        Sirius          Spica          Avior      Bellatrix
> Dubhe
> UT:        22:15:30       22:17:02       22:19:00       22:19:45
> 22:20:12
>           ---------      ---------      ---------      ---------
> ---------
> Hs:         28 16.3        42 20.6        15 55.3        13 26.5        37
> 56.1 +/- ie: -       2.5    -       2.5    -       2.5    -       2.5    -
> 2.5 -dip:   -       2.9    -       2.9    -       2.9    -       2.9    -
> 2.9
>           ---------      ---------      ---------      ---------
> ---------
> Ha:         28 10.9        42 15.2        15 49.9        13 21.1        37
> 50.7 +/- ro: -       1.8    -       1.1    -       3.6    -       3.5    -
> 1.2
>           ---------      ---------      ---------      ---------
> ---------
> Ho:         28 09.1        42 14.1        15 46.3        13 17.6        37
> 49.5
>
> GHA:         109 29.3         9 51.2        86 01.4       130 33.5
> 46 01.0 Decl:   -   16 43.2    -   11  9.8    -   59 30.9         6 20.8
>      61 45.3
>           ---------      ---------      ---------      ---------
> ---------
> Hc:         28 32.3        40 51.1        14 56.3        14 21.1        38
> 54.8 Zn:           243.9          115.4          196.2          273.8 4.8
>
> Int:         23.2 A
>
> Big intercepts! Wow. If I plot these, I end up near 10d 53'. Using this as
> a new AP, I get:
>
> Star:        Sirius          Spica          Avior      Bellatrix
> Dubhe
>           ---------      ---------      ---------      ---------
> ---------
> Hc:         28 05.1        42 10.1        15 37.1        13 18.0        37
> 59.6 Zn:           244.8          115.1          196.7          274.2 4.2
>
> Int:          4.0 T          4.0 T          9.2 T          0.6 A
> 10.1 A
>
> Much better intercepts. The fix reads 9d 50'N 53d 00'W.
>
> > |2)  What is the TC and distance to Barbados(13d 10.0'N  59d 20.0'W)? --
> >  ----------------------------------------------------------------
>
> From 4mulas.txt (an attachment to
> http://www.i-DEADLINK-com/lists/navigation/9805/0001.html), part 1, mid-latitude
> sailing:
>
> Fix L1:           9 50.0'N          53 00.0'W
> Destination L2:  13 10.0'N            59 20.0'W
>                  --------           ---------
> Diff.:            3 20.0'N           6 20.0'W
>                l = 200.0'N      DLo = 380.0'W
>
> 1/2 l:    1 40.0'
> + L1:     9 50.0'
>         ---------
> Lm:      11 30.0'
>
> 1) p = DLo * cos Lm
>      = 380 * cos 11 30.0'
>      = 372.37 nm
>
> 3) tan C = p / l
>    tan C = 372.37 / 200 = 1.86
>    C = 61.75 = 61 45.5'
>
> Thus the course is (360 - 61 45.5') = 298 degrees.
>
> 2) DLo = p / cos Lm
>        = 372.37 / cos 11 30.0'
>        = 379 nm
>
> > |We continue sailing maintaining the same speed and True
> > Course with an
> > overcast
> > sky. Then, with the navigator on deck waiting for an opening for a Sun
> > shot, we see a spot of land on the horizon ahead. It is 20/05/2000 @
> > 12:13:00ZT.
> >
> > 3)  What is the DR position?
> > --  ------------------------
>
> What is a good resource to convert from ZT to UT given one's lat/lon?
>
> > 4)  What day of the week is this?
> > --  -----------------------------
>
> According to my calendar, it's a Saturday..
Dan Hogan
dhhogan@XXX.XXX

   

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