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    Re: Is most probable position (MPP) a dangerous misnomer?
    From: John D. Howard
    Date: 2018 Oct 29, 07:59 -0700

    David,

    What I was saying was that MPP is not a dangerous misnomer but Old Fashion.  Without looking at a GPS how would you know if you were within one or two miles or even 10 to 20 miles?

    I flew the world well before GPS or even ( in our aircraft ) INS.  The nav would give me a position ( fix ) but would also qualify it.  " A lot of turbulance, so the fix is off by a bit."  Not once in over 40 years did anyone give me error circles or standard dievations or the like.  The NAV had no way to qualify the error in terms of miles from our true position because no one knew our true position.  When INS units were installed in our aircraft they removed the Nav and the nav station.  The pilots would fly around the world, knowing that the longer the flight, the more error in the INS fix but, once again, no one knew our true position.  When within range of land and radio nav aids the INS would update itself and be pretty close upon landing.  Even flying in the USA along airway, on course, we could be left or right 2 or 3 miles.

    Never sailed the sea but I think the navigation was the same - out of sight of land how would you know your true position?  Before GPS, I think the navigator would have a sense of how good his fix was but no way to qualify it in terms of distance from ( unknown ) true position.

    Today, does a weekend sailor keep a log, plot DR, do running fix, estimate wind and drift and plot a MMP or does she do all that then look at her GPS and plot a fix?  Once again, I think the concept of MPP is old fashioned - not dangerous.

    John H.  41N 100W

       
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