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    Re: 'Intentional Error' Method of Navigating to Destination.
    From: Hewitt Schlereth
    Date: 2009 Nov 10, 17:24 -0400

    I learned it as "aiming off". The technique even figures in fiction -
    The Riddle of the Sands (by Erskin Childers?), for one. There may well
    be others.. -Hewitt
    
    On 11/10/09, douglas.denny{at}btopenworld.com
     wrote:
    >
    >  Further to the Harold Gatty / Sir Francis Chichester comments:-
    >
    >  I have found Gatty's book, and intended to scan the relevant bit but both 
    the scanners I have will not function. There is something wrong with Mr. 
    Gate's hated Microscoft XP operating system in my ancient computer so that it 
    cannot find the TWAIN drivers.  It's time to consider an Apple Mac as 
    replacement.
    >  =========
    >
    >  The mention of the 'intentional error' method is on page 70 of Harold 
    Gatty's book  "Nature is your Guide",  where he mentions using it, (written 
    in 1957).
    >
    >  It is a curious co-incidence that Gatty's flight in Siberia mentioned in 
    his book using this 'deliberate offset course to destination' method was in 
    1931;  and so was Francis Chichester's flight across the Tasman Sea in 1931, 
    (described in his book first published in 1964 - so Gatty is the first to 
    describe it in print in 1957).
    >
    >  I suspect the method was a well-known 'trick' discussed at the time in 
    navigating circles of these pioneers of aerial navigation.
    >  ----
    >
    >  I'll quote the relevant portion of Gatty's book:-
    >
    >  " .... there is an additional means of straight-line navigating that is 
    worthy of mentioning here - the method of the intentional error, the method 
    of aiming (when the conditions of the journey permit) somewhat askew of the 
    final target.
    >
    >  I can recall from my flying days a successful use of this simple trick.  I 
    employed it on my world flight with Wiley Post in 1931, when we were in an 
    area in which there were no distinguishable features to relate to the map.  
    The area was Eastern Siberia; and we left Irkutsk for a 'leg' of some  1100 
    miles with the intention of refuelling at a small airfield on the bank of the 
    Amur river.
    >
    >  The last several hundred miles of this leg were over Northern Muncuria - 
    over high grass country with no towns, no roads - indeed precious few 
    distinctive features of any sort.  We knew that we were unlikely to land much 
    before dusk and that the airfield was not lighted.  We could not afford to 
    waste any time looking for it.  I purposely set a course to hit the Amur 
    river ten miles to the left of our destination.  When we reached the river I 
    told Wiley Post to turn right.  We rounded a bend and there lay the airport.  
    We made our landing with just enough light.  Wiley Post could not understand 
    why I was so definite about to turning to the right until later I explained 
    it to him.
    >
    >  There has been no check points for the last part of our route; and our maps 
    were very questionable.  If we had set a course directly to the field and had 
    missed it when we reached the Amur river, we could have used up all our 
    daylight by turning in the wrong direction......
    >
    >  ..... this shows the the value of the calculated intentional error - a 
    simple method which can bring the traveler to the base line of his desired 
    goal in no doubt whatever (unless he has been guilty of a really gross 
    miscalculation) as to which way to turn.  Any normal unconscious deviation is 
    swallowed up in this intentional margin; by purposely aiming for a point 
    either to the right or to the left of his objective, the navigator eliminates 
    this uncertainty and is sure of his homefall. "
    >
    >  ----------
    >
    >  Douglas Denny.
    >  Chichester.  England.
    >
    >
    >  >
    >
    
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