"Brian Salt" wrote in message
k.co.uk...
It appears that the meteorologists used balloons as part of the data
collection, but at that time they had no radar, etc., to help with
finding
the height of the balloon.

The control tower of this airfield was equipped with two pillars to
which
theodolites could be attached/mounted. Apparently, these were used to
determine the angle of ascent and the height of the balloon.

Does anyone have any idea how that could be done, given (as far as I
can
see) that you need the horizontal distance to the balloon as well as
the
angle to find the height? Or would the use of two theodolites
simultaneously, spaced at about 22 feet apart, allow the height to be
found without needing the horizontal distance?

.... 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. This method requires more time in preparation, and
involves the employment of at least three observers in telephonic
communication. Some improvement is accuracy is obtained for low
altitudes, but in view of the extra time and personnel required, the
method is not suited to the routine observations at an ordinary station
".

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: also, the 22 foot baseline
sounds too short for the above method to be used accurately - though I
could be wrong on that - I suppose if the azimuth readings were taken
very accurately, then a downwind position could be determined OK.

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)

Martin.


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