Papa3 wrote:
Correct me if I'm wrong, but regardless of whether pressure altitude and
Geometric (ie. GPS) altitude differ during a flight, if you use a constant
reference (ie. always use GPS), then the consistency is similar, at least
over the altitudes we typically use.

Yes, you are wrong. If you look at the equations for converting
pressure to altitude, you'll note that one factor is the average
temperature of the column of air between the reference altitude and the
altitude at which the pressure is being measured. Altimeters,
barographs, and flight recorders are calibrated to a specific sea level
temperature (15C) and a specific temperature lapse rate (0.002C/ft), as
determined by the International Standard Atmosphere. These conditions
almost never apply to real world soaring flights, as we generally fly on
warmer days with higher lapse rates. At 10000 feet above my home field
during the summer, my properly set altimeter typically reads 500 or 600
lower than my true altitude, which can easily be verified when flying
near peaks with known elevation. This can also be verified by looking
at IGC files from an approved flight recorder, the divergence between
GPS and pressure altitude (adjusted for the different baselines)
generally increases with altitude, and the amount of divergence will
vary on a day to day basis.

Well, I think this is exactly the point. The OO system has ALWAYS been an
honor system. There are dozens of very significant records out there where
wives/husbands/best friends have handled this critical function. If that's
not truly an "honor system", I don't know what is. Unless the FAI is
willing to mandate that OO's be impartial third parties who are subject to
random lie detector tests (with violations punishible by having to sit in on
committee meetings to discuss COTS proposals), then I come back to my
primary point. There is effectively NO DIFFERENCE in the degree of
security between the two methods. There are differences in the type of
technical prowess required to defeat the system, but level of security is
effectively the same.

Actually, the OO system was much stricter in the past than it is now.
It has relaxed over time due to changes in the nature of the sport, and
the circumstances under which we fly. One of the reasons for requiring
increased security for flight recorders (and the requirement that they
be used for world and national records), was to compensate for the fact
that it was no longer possible to demand or expect completely impartial
observers.

At the end of the day, what we've done is exactly the mistake I pointed out
in the beginning. We've allowed paranoia over a few folks who may want to
fudge their gold distance flight or silver climb lead to a situation that
literally requires people to stick with 1940's technology or fork over an
extra $500 for an "approved" logger. For this cost we get what exactly?
The satisfaction in knowing that, if a guy wants to fly his Silver Distance
in a Nimbus IV, at least he didn't cheat? Am I the only one who sees a
certain irony in this????

It has been pretty well established that a greater percentage of active
pilots own flight recorders now than owned barographs in the past. I
have loaned out personally owned flight recorders, and I know several
others who have also done so. Just about every club that I know if in
my area has flight recorders available to their members. Quite a few
commercial glider operation rent them for a small fee. And, of course,
one can still use a camera and barograph. I have a barograph in my
closet I haven't been able give away to anyone in the area.

But, you know what? I think the IGC *should* allow use COTS GPS units
for badges with some restrictions. The problem that you (and others who
have proposed this) are up against is that it will take a good deal of
work to convince those who really matter. Frankly, the proposals I've
seen so far have been rather poorly argued and incomplete. I don't
think anyone has yet bothered to do the homework necessary to come up
with a proposal that might be taken seriously.

Marc