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    Re: Combine DR and celestial LOP
    From: Frank Reed
    Date: 2013 Apr 1, 16:19 -0700

    John Karl wrote:
    "what navigator wants to be right only 90% of the time. (Well, 90% would be great for treasure hunts.) So for normal practical navigation the question is, what is the outer-most boundary of these combined areas, not one-sigma boundary, but the reasonable absolute maximum."

    Outer-most boundary?? Reasonable absolute maximum?? Oh good lord...

    I am disappointed to see this sort of mumbo-jumbo... and also a little nostalgic. I feel like I have just been plunged back in time three decades to the early years of financial risk management. It's such a seductive logic: "don't tell me probabilities; tell me my 'bottom-line' risk. What is my 'worst-case' scenario given our current portfolio?" Simple. There is no such thing. On a bad day, though the probability is very low, you could lose the whole show. But they don't want that. They want someone to tell them their "reasonable absolute maximum" risk, in John Karl's words. This sort of thinking applies no better in navigation than in financial risk management. This isn't navigational science. This isn't navigational artistry. This isn't the "good judgment" of a wizened old salt. If you can't understand that this is all about probabilities --all about "odds" of being within some distance of a supposed position-- then you should stay at home.

    -FER


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