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Your example from the CG test intrigued me because it's a case of
altitudes so high you can put the GPs down on a plotting sheet, swing
the arcs of the zenith distances and use the DR to choose which of the
two points where the arcs intersect to decide which point is the fix.

I did this on a VP-OS Universal Plotting Sheet - the one where a NM is
about one millimeter. Because I don't have a compass large enough to
draw an arc with a radius of over 152 NM, I couldn't change the scale.

Anyway, I came up with a position of 19*22' S, 6*38' E, which is very
close to the 1200 DR of 19*20.3' S, 6*39.3' E. Closest position on the
answer sheet is A.

Check me on this, if you've got the time.

Thanks, HewS

On 7/16/08, Anabasis  wrote:
>
>  Exercise 16  Position near Noon by High Altitude Sight
>
>  As promised, I am posting a couple of Celestial Navigation problems
>  that were presented to me on my Last US Coast Guard Examination.  I am
>  quoting them verbatim and will give a list of reference materials
>  available in the exam if people wish to replicate my exam conditions.
>  Reference materials:  1981 Almanac, Bowditch Vol 2- 1981 edition, HO
>  29 Vol 2, Plotting sheets, plotting tools, non-navigational
>  calculator, writing instrument.
>
>  Here is the problem and multiple choice options:
>  "On 13 November 1981, your 1030 ZT DR position is Lat 19 deg 03'S,
>  Long 6 deg 34'E.  You are on course 164 deg T, speed 12 knots.  You
>  take the following observations of the Sun:
>  Zone Time       GHA             Declination     Observed Altitude (Ho)
>  1112            351 deg 55.4'   S 18 deg 00.4'  88 deg 08.0'
>  1121            354 deg 10.4'   S 18 deg 00.5   88 deg 33.9'
>
>  What is the 1200 position?"
>
>  A)      Lat 19 deg 22.3'S, Long 6 deg 37.8'E
>  B)      Lat 19 deg 20.1'S, Long 6 deg 41.4'E
>  C)      Lat 19 deg 17.6'S, Long 6 deg 39.2'E
>  D)      Lat 19 deg 15.8'S, Long 6 deg 36.8'E
>
>  As a note, the answer MUST be one of the multiple choice options.  If
>  your fix does not match the choices, you must choose the one you think
>  is most correct.  As you can see, this is mostly a plotting exercise.
>  I suggest using the largest scale plotting sheet you can muster.
>
>  Jeremy
>
>  >
>

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