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Brian Salt · November 13th 04, 04:32 PM posted to sci.geo.meteorology

In article ,
(Martin Rowley) wrote:

... this from "Meteorology for Aviators", HMSO, dated 1939, in the
section dealing with Upper Winds:

" The double theodolite method ... by observing the balloon
simultaneously through two theodolites set up at the ends of a measured
base line, the height of the balloon may be calculated directly from
the various observed angles; for the bearings give a 'fix' to the
position of the balloon. snip

That is the method I felt would be used, but, as you say, the baseline of
22 feet is not a useful distance.

I'm curious: *which* airfield in Devon are we talking about? I can't
think of one where the above would be justified - the vast majority of
upper wind finding (in UK) was done on the single theodolite method
using an assumed rate of ascent of a balloon: snip

Harrowbeer Airfield, some 9 miles north of Plymouth.

So what is the single theodolite method?

Just a though, was one pillar for a theodolite, and one for a Finemann
Nephoscope - which would also need a pillar? (This latter was also used
for finding upper winds - by chasing features in medium and upper
clouds)

There is no mention of a Nephoscope is the information we have - and it is
not mentioned on the plans of the watch office/control tower.

Perhaps the need for 2 pillars was to use whichever would be better to
avoid the projection of the balloon filling room, which projects some 8
feet above the roof upon which the pillars are fixed. I can't imagine that
the room for cause any obstruction, but maybe it was 'belt and braces'!

What would a balloon have be used for, given the technology available in
1941-42? Determining cloud base, I suppose, as well as finding the upper
winds?

Brian.