NavList:

I have read with interest the discussion on the ever-troublesome cocked hat, and the difficulties associated with assigning a most probable point (or even a least improbable point).

If one takes sights on two celestial objects - where he feels equally confident in the quality of the sights - and uses Frank's equation for determining the error elipse (http://fer3.com/arc/imgx/error-ellipse-ratio.jpg.thumb.jpg), to what extent can one say that he has pretty much what he needs to come up with as good a fix as can be had?

That is to say, if one takes a sight on a third object, reduces and plots it, could he say that he has done more work with no significant probability that he knows more about his actual position than he had after plotting his initial two LOPs?

And if a 3rd LOP represents a poor navigational return on time-invested, presumably a 4th LOP is even less worthwhile?

Bob