Please excuse my ignorance but from what you have said
about the inaccuracy of pressure altitude recorders
is GPS altitude more accurate than pressure altitude.
On the traces that I have from my logger the two traces,
pressure and GPS are fairly consistent in their difference
at lower levels. GPS trace is QNH, baro is QFE. Is
the divergence with height a function of the inaccurate
pressure trace with an accurate GPS trace or are both
subject to inaccuracies for different reasons?


At 18:30 24 May 2004, Marc Ramsey wrote:
Tony Burton wrote:
Marc, it occurs to me that this may not necessarily
be so as long as the
IGC rules for FRs don't have to change in order to
introduce a specific
COTS GPS. For example, each FR approved by the the
GFAC comes with an
'approval document' which delineates how that FR must
be used, OO actions,
etc.

So, say that some Garmin GPS is ICG-compliant except
for the barograph
function. Could not such an FR be approved by the
IGC GFAC committee with
the restriction in its approval document that it could
not be used for
height evidence?

No, since pressure altitude recording capability is
a non-optional
requirement of the Technical Specification (see sections
2.4 and 2.6.5).
In any case, I believe all FAI badge-related flight
performances
require altitude evidence, with the sole exception
of the 5 hour
Silver/Gold duration.

Marc