Celestial navigation explained - page 6
LOPs, cocked hat and common sense
Common sense is judgment without reflection, shared by an entire class, an
entire nation, or the entire human race (Giambattista Vico (1688-1744), Italian
philosopher)
The observer astronomic position O is at the intersection of the 2 LOPs.
With 3 sextant observations, you get 3 LOPs and if you are very good and very
lucky at the same time, you could end up with LOPs intersecting like this:
Most often, however, you will get LOPs intersecting like this:
This triangle is known as a cocked hat 
after
its resemblance to the common three-cornered hat of the times when these
navigation techniques were developed.
Where is exactly the observer astronomic position O?
Well, the common sense is telling us that O is exactly in the middle of the
triangle:
Unfortunately, the common sense is seriously misleading here...
| If (and only if) the observations azimuths are
spread over more than 180°, then the most probable position (MPP) is inside
the cocked hat, but with a probability of only 25%! |
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