Gene, we aren't doing ballistics here; we only want
to get close enough for the eyeballs to do the proper
adjustments. For badge flights we try to exceed the
minimums enough to make up for instrument errors; for
record flights we must exceed the current record by
a percentage that should account for these relatively
minor distances.

It's nice that someone is turned on by all this precision;
in my mind it has all the usefulness of train spotting
with respect to practicality in soaring.

At 15:12 28 August 2003, Gene Nygaard wrote:
Maybe Eratosthenes still thought the Earth was a near-perfect
sphere,
when he made a fairly reasonable calculation of its
diameter Maybe
Columbus wasn't even aware of the true shape of the
poles.

But we've known about the flattening at the poles for
about four
centuries at least, probably longer than nautical miles
have existed.
Certainly since long before the French scientists in
the 1790s
designed the meter to be 1/10000000 of the distance
from the equator
to the North Pole.

We do, of course, have 360 degrees around the equator.
When we agree
on a starting point (e.g., the point where it crosses
the meridian
through Greenwich, England, the one most often used
now), any
particular place will always be the same number of
degrees from it.

We also have 90 degrees between the equator and either
pole. The
equator is always 0 degrees and the poles 90 degrees.
But in between,
there are at least three different ways of measuring
latitude:
geocentric latitude (the angle formed at the center
of the Earth),
geodetic latitude (the one normally used, the angle
formed between the
line normal to the tangent of the ellipsoid and the
axis of rotation),
and the angles used in the parametric formulas representing
an
ellipse. These don't agree with each other at any
place not on the
equator or the poles.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/