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Warning: a bit off topic. We recently establish a permanent network of GPS receivers in
the Canadian high arctic to study the ionosphere. Click here if interested to learn
more: .
-- Richard Langley

Quoting Robert Eno :

>
> G'day Bruce,
>
> > When you used bubble sextants on the water did you use the averaging
> > mechanism?
>
> No. They are not worth the effort. The averaging mechanism was designed for
> the relatively predictable motions of an aircraft; not the pitching, yawing,
> bouncing of a small vessel.
>
>
> The least motion I have ever seen in a vessel is flat calm
> > with 35 thousand tons of iron ore in the holds with a ship with a flat
> > bottom. You could almost shoot pool if you had a table.There was some
> > motion, but certainly less than you would find in an aircraft.
> >
> I have heard that you can balance a dime off the taffrail of a supertanker
> but the vessels I have attempted bubble sextant observations from were small
> and certainly not as stable as a 35,000 tonner! Actually, I would love to
> have an opportunity to attempt this one day, to see what it is like. But
> even at that, I have been sitting in my own boat in flat calm water with
> nary a discernable motion and the bubble still tended to be skittish.
>
> > I like your comet about the celestial navigation in the far north, as my
> > father was a bush pilot in Northern Quebec in the 60's. Magnetic compass
> > was questionable. It was all floats so you never even got to set the
> > gyro to a handy airstrip direction.There was no VOR, and few radio
> > stations to pick up on the RDF.  On top of that the land is featureless
> > and the ceiling is always low. His joke was if he took the Beaver up
> > over 1000 feet he would get a nosebleed since he was so unused to it.  I
> > gather the GPS has made things better, but it too suffers in high
> > latitudes, although I can find no published facts on this on the web. He
> > didn't have an astro-compass on his plane.
> > I have a friend who often finds himself in the North as a ship's
> > navigator who says the GPS has problems because the satellites get too
> > close to the horizon. Even the the Gyros (both mechanical and FOG) get
> > wonky too. Fortunately, the sun is always up when he is there.
> >
>
> GPS is immensely popular in these parts. Most hunters now have them strapped
> to their skidoos. I have used GPS up in Resolute Bay and Ellesmere Island
> without any apparent ill effect. That being said, I cannot say that my use
> of GPS in these parts has been extensive so I can only comment on my
> experiences during my brief interludes up there. In the southern and
> mid-Arctic; that is at Latitudes of 60 - 70 degrees, I have found GPS to be
> very reliable. Satellite phones are another matter altogether...
>
> I have a couple of astro compasses in my collection. At one time, they were
> mandatory on all aircraft flying up here but I am not certain if this is
> still the case. Regardless, I seriously doubt if most of these young pilots
> would know the difference between Venus and a streetlamp. It is, from what I
> have observed, all about button-pushing.
>
> Incidentally, do you have a copy of Kieth Greenaway's "Arctic Air
> Navigation"?  If not, you should pick up a copy. Published in 1952, it was
> at the time, on the leading edge of air navigation in the polar regions. It
> was all astro compass and sextants back then.
>
>
> Robert
>
>
>
> >
>


===============================================================================
 Richard B. Langley                            E-mail: lang@unb.ca
 Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
 Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
 University of New Brunswick                   Fax:      +1 506 453-4943
 Fredericton, N.B., Canada  E3B 5A3
     Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===============================================================================



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