OT: Navigation Aids (was Long term data storage) (was: Disasters

From: Geoff Roberts <geoffrob_at_stmarks.pp.catholic.edu.au>
Date: Tue Jan 19 12:30:06 1999

> Date: Mon, 18 Jan 1999 21:46:00 -0500
> Reply-to: classiccmp_at_u.washington.edu
> From: Ward Donald Griffiths III <gram_at_cnct.com>
> To: "Discussion re-collecting of classic computers"
> <classiccmp_at_u.washington.edu>
> Subject: Re: Long term data storage (was: Disasters and Recovery

> Jim Strickland wrote:

> On-board instrumentation on German aircraft was not that good

I beg to differ. The Luftwaffe had a very good radio navigation system
mostly in place at the start of the war, a development of the Lorenz Blind
Landing system (essentially a VHF Aural Range or VAR) called " Knickebein"
(Crooked Leg). Knickebein was used to allow Luftwaffe aircraft to navigate
with considerable accuracy over England, and made night bombing worth the
effort. It was detected and (ultimately) jammed, and was essentially unuseable
after July 1940. A constant race (The "Battle of the Beams") went on between
British Scientific Intelligence trying to figure out what new radio navaids
were being developed and used, and means to jam them, and the Germans trying
to come up with replacements for navaids that were compromised or jammed. A
replacement for the jammed Knickebein system was instrumental in the
destruction of Coventry. "Pathfinder" aircraft of KG100 using the then new
"X-Gerat" system marked the target with incendiary devices so that the recently
de-Knickebeined main force could locate and bomb the target. This took place
by night, so visual navigation was not being depended on.

> (as it was also not that good on English or American planes early in the War)

This is certainly true. The RAF heirarchy were still of the opinion that it
was possible to navigate accurately at night by astronomical means, in the same
way that ships did. This was ultimately proven to be wishful thinking, but the
attitude delayed the introduction of navaids like Gee and Oboe for some time.

> Landmarks were often crucial.

Useful by day, but the Germans found that bombing during the day was perilous
in the extreme, an experience shared by the US Air Force over Germany somewhat
later. At night landmarks have little practical use. Unless they are on fire
of course. Interestingly, the Coventry raid was made during a full moon, and
anecdotal reports from Luftwaffe aircrew suggests that they could probably have
found the target visually, particularly after it was well alight.

Much of this was detailed in a BBC TV series called "The Secret War", and in a
book of the same name. Another book by the then head of British Scientific
Intelligence, R.V. Jones "Most Secret War" goes in more depth into this and
other fascinating things.

To get us back on topic, there is considerable time given in these sources to
the means used to crack the codes generated by the German Enigma and
Geheimschreiber encrypting machines. Arguably the first true electronic
computer, Colossus, was built specifically to deal with the Geheimschreiber,
and had contributions to it's design by the legendary Alan Turing himself..
The book "The Ultra Secret" goes into the whole business of the Enigma codes,
and the breaking of them, which aided the Allies enormously throughout the war.
I tried to name my first VAX "Colossus" in it's honour, (and because of it's
SIZE - it's a 6000) but was foiled by the 6 character limit in VMS/Decnet host
names. So I had to settle for ENIGMA.

Cheers

Geoff Roberts
Computer Systems Manager
Saint Mark's College,
Port Pirie, South Australia
geoffrob_at_stmarks.pp.catholic.edu.au
Received on Tue Jan 19 1999 - 12:30:06 GMT