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Douglas wrote:

"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)."
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Chichester first published "Seaplane Solo" in 1933 describing the technique.

Coutinho published his description in 1922 and also presented it to the Pope! 
It received much coverage in Portugal where his name is well known as a 
national hero, following in the footsteps of Vasco Da Gama and other 
Portuguese navigators.

Both Coutinho and Chichester used celestial LOPs which is different from the 
method described by Gatty. (BTW, I have Gatty's "The Raft Book" which is very 
interesting and describes several emergency navigation methods.)

But the use of celestial LOPs with a deliberate offset to find a landfall is 
nothing revolutionary since the technique had been use for centuries. In the 
olden days, before accurate time was available, the only LOP available ran 
east and west establishing a latitude at noon. Sailors would aim off to the 
the east or to the west of their destination and then establish that they had 
intercepted the LOP (the parallel of latitude) by a noon observation and then 
sail east, or west, following the LOP to the landfall, a method known as 
"latitude sailing."

gl










douglas.denny@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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