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    Re: sextant without paper charts
    From: Richard B. Langley
    Date: 2008 Nov 9, 17:12 -0400

    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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