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Thanks to Douglas Denny for making it clear which expedition he was
referring to.

In the paper he linked to, the claim was made-
"each leg of a traverse was maintained to �2�, and often within 0.5�,. It 
was found in practice that errors were distributed randomly to port and 
starboard, the net error being small. Stages through areas of rough sastrugi 
were maintained within 3�.
When compensating action followed frequent checks of heading, the overall 
track lay within 0.5� port and starboard of the course steered."

However, that needs to be taken with a pinch of salt in view of the earlier 
statement-

"(c) Course adjusting. Periodic checks of track were carried out in order to 
minimize course error, the interval being dictated by the degree of accuracy 
required. The driver aligned the vehicle precisely along the line of his 
track as the vehicle came to rest. Reference to the astro-compass or 
magnetic compass (at rest) then demonstrated any deviation from the planned 
course. A compensating slight alteration of heading over a calculated 
distance corrected any error."

The interval between those "periodic  checks of track" was nowhere stated.
We have no idea what it was. The technique described implied the availabilty
of either an astro-compass (and a Sun) or else a usable magnetc compass (at
rest). If the Sun could be seen, the technique wasn't necessary anyway; the
bearing of the Sun could have been used to steer a course. If the magnetic
compass could be used (even if only at rest), they were not at, or very
near, the magnetic South Pole. In the Fuchs case, neither was available.

The claimed accuracy was no more than that achieved between those "frequent
checks of heading", which provided the essential feedback. Without such
checks, how viable was that procedure, compared with what the Fuchs
technique achieved? We are not told, and have no way of judging the matter.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
----- Original Message ----- 
From: 
To: 
Sent: Sunday, August 23, 2009 1:45 AM
Subject: [NavList 9604] Re: Lost people DO follow circles, says research


|
| Oh curmudgeonly one of little faith!
| It is as I said.
| A mirror mounted on the vehicle allowing a good view behind.
|
| The expedition was the Australian Antarctic Research Expedition in 1960.
|
| It seems they were cleverer than the Brits with their expedtition when
they were putting out sticks to steer by, and did not like getting out in
the freezing cold to pick them up again in all the snow and ice and so
devised this method.
|
| I note having read it again they used a stick on the vehicle for reference
in the line of sight of the view of the mirror: effectively doing the same
job as getting out playing around with sticks in the snow.
|
| Appparently they could track within + or - half a degree.
|
| Quite a simple clever idea.
| See the enclosed pdf file.
|
| Douglas Denny.
| Chichester. England.
|
| =====================
|
| Original Copy:-
|
| Douglas Denny wrote, in ]9852]-
|
| "In the 1950s (or was it 60s - can't remember)  the Antartic expeditions
| using caterpillar tracked vehicles to get to the Sotuh Pole used a mirror
| set-up in the driver's vision of the front vehicle, to enable him to look
| backwards so the driver could look back along his track made in the snow,
| and thus keep a straight line ahead.  It was very effective apparently as
he
| was making a continuous back-bearing on his own tracks with which he could
| see immediately if he veered off track."
|
| ========================
|
| I presume Douglas Denny refers to 1958, when the trans-Antarctic
expedition
| were trying to get from, not to, the South Pole, in the last stages of
their
| crossing. This took the party near the South Magnetic Pole, when their
| magnetic compasses (at least, those aboard their tracked vehicles) became
| useless, and with sky overcast, the Sun position was of no help..
|
| My reading of the technique, as described by Fuchs and Hillary in their
book
| "The crossing of Antarctica", bears little relation to that description
| given by Douglas Denny above. I can find no mention of using alignment, in
a
| mirror, with the vehicle's own tracks, as he described. If it's there, or
| perhaps in an account of another expedition altogether, a reference would
be
| helpful.
|
| Having somehow established an intended direction and marked it with a pair
| of flags, they continued it indefinitely by having a collection of marker
| flags carried in the leading vehicle. Before the flags behind them had
| disappeared from sight, one of the team would get out and place a new
marker
| precisely aligned with those that had gone before. In this way, they kept
a
| chain of four flags constantly in view. As I see it, three flags would
have
| sufficed, but no doubt four provided belt and braces.
|
| The flags, when no longer needed, were collected by the trailing vehicle,
| and eventually recycled.
|
| In this way the straight path could be extended on and on, and a large
| radius of curvature could be maintained. The angle-of-bend, at each new
| flag, was kept small, being limited (in radians) to the error in aligning
| each new flag with its predecessors, divided by the spacing between the
| flags. Hopefully, that error would not always be in the same direction,
but
| inevitably, an error in direction would accumulate. However, the sky
cleared
| after about 100 miles of travel had been accomplished by this technique.
|
| George.
|
| contact George Huxtable, at  george---me.uk
| or at +44 1865 820222 (from UK, 01865 820222)
| or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
|
| 
File: 

   

|
|
| |


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