Here is some insight to Polar Navigation and it's application...
Thanks to Bob Nyden who proves that you can get there from here..
He was a navigator in VXE-6 along with Bob O'Keefe from '71 thru '74. He
forwarded part of an email to me in which you asked about grid navigation:
>Hi Bob O'Keefe, ( same as 644 navigator ? )
>Thanks for the neat input to the connie page via Noel.
>Been looking for someone who understands polar grid navigation
>to make the connection from celestial to grid.
>It makes sense but I just don't connect the dots as yet.
>Am somewhat OK with celestial from going to sea.
>Would make a good piece on www.radiocom.net/vx6 if ya like..
>73s from Dave Riley, VX6, 64-67, 644 Radio
=
Here is a part of a long story I once wrote about flying from Christchurch to
the Ice. We've reached cruising altitude and turned on course abeam 4YA (Oamaru
East):
Now it was time to switch over to grid navigation. Over most of the world the
familiar magnetic compass, when combined with suitable corrections for local
variations, is perfectly adequate. But as one approaches the poles, the magnetic
compass becomes less and less reliable and the corrections larger and more
frequent. So as a convenience, charts of the polar regions have been overlaid
with an artificial square grid which ignores magnetic influence and eliminates
another bother of standard charts, the convergence of lines of longitude at the
poles. This grid is arranged so that north and south lie along the great circle
which creates the Greenwich or 0° meridian, and the 180° meridian which
roughly creates the International Date Line through the Pacific Ocean. On the
C-130, our gyro-driven compasses, which were normally tied to the magnetic
system, were reset to align with the grid system whenever we headed south to
Antarctica. As a matter of convenience and safety the conversion usually took
place just after passing the last reporting point associated with New Zealand,
namely Oamaru East. Thus if anything went wrong with the compasses during the
switch, we could easily return to base using the backup magnetic compass. About
the only problem with grid nav was that it relied on a very stable gyro compass,
one that precessed (gained error) very little. Normally ours could be depended
upon to vary only one degree an hour, but only reference to the outside world,
usually by taking a sight on a celestial body, could verify that the gyro was
holding the proper grid heading. I was hoping that we would be able to take a
sight within a few hours, because for every degree of compass error that I
couldn't detect, we would drift four or five miles off course every hour.
An ironic result of the arbitrary alignment of the grid system was that our
southerly true course became a northerly grid course. In fact the course to
McMurdo now was 354° grid, almost dead on "north." It always amused
me to watch visitors to the flight deck as they sorted through the imposing
array of instruments until they found the compass, only to discover that somehow
to go south you had to go north!
Grid nav was really great--much easier than using the magnetic compass because
you didn't have to worry about magnetic variation corrections, and the grid
printed in nice regular 30-nautical-mile increments (half a degree of latitude).
I think the Air Force used grid nav all over the world. Certainly the nav charts
all have the grid printed on them. Celestial worked much the same as in the
"real" world because the grid is aligned to the same true north.
Estimated positions for calculations were still the standard latitude and
longitude. The trick was in calculating the direction you had to point the
sextant to find the celestial body, that is the azimuth angle (Zn). What you did
was add your East Longitude (or subtract West Long.) to the normally found
azimuth angle and use that and your grid heading to find the bearing to the
body. This is akin to the rule for converting magnetic heading to true heading:
"magnetic-to-true-add-East (variation)," but here it's
"true-to-grid-add-East (longitude)." (A similar calculation is done to
find the local hour angle (LHA) when computing the sextant altitude (Hc),
whether you're using grid or not.) It was easy (and important) to check the
gyros for precession by calculating the bearing where the Sun should be relative
to the airplane and comparing that to the actual azimuth angle. At the Pole, it
was necessary to use the skiway alignment as a reference to check the gyro
because there was no telling what line of geographical longitude you were on.
Hope this helps, Dave. If you want more info, I'd be happy to try.
Bob Nyden
OAE '71-"74