Chip Bearden wrote:
OK, I'm a layman, late middle age, and little slow. What am I missing?
The pressure altitude (per the altimeter, at least) is less accurate
than the GPS altitude? By up to 1000 feet at Western USA soaring
altitudes? In the old days, we used a start gate that evaluated
optically how high we were above the ground. Assuming no one tripped
over the guy wires, that actual altitude stayed the same during a
contest. Now we're evaluated using a pressure-altitude-recording
device that may or may not reflect how high we really are?

As an aside, while I flew a few contests using optical start gates, I
can't remember how one used to avoid bad starts. Did we dive through
with enough of a buffer beneath the stated maximum start altitude to
allow for the pressure altimetry error, or did we generally start lower
(so the wing numbers could be read through binoculars), thus keeping
error pretty small?

Marc