On Feb 25, 12:53*pm, "PCool" wrote:
Everyone agree on the fact that
the GPS Altitude is not accurate.

Actually, what I took away from this discussion is that the GPS
altitude is MORE accurate with regard to actual height above the
ground but not necessarily equal to pressure altitude in the real
world. So what I hear now is the Certified Flight Recorder crowd
saying we shouldn't use GPS altitude even if it's more accurate, for
the reason that it's not comparable with the way we've always
evaluated badge and record claims in the past. This seems precisely
the opposite argument used to justify GPS flight recorders in the
first place: i.e., that their 2D positional accuracy was better so we
simply *must* use it.

I agree airspace incursions are a different issue. But in the old
days, we could only measure incursions on the Y axis (i.e. altitude)
anyway. Would it be so bad if now we could only measure them on the X
and Z axes (i.e., lat/long)? At most contests where I've flown
recently, including US Nationals, that's been the case: i.e., we're
not allowed to fly over or under most airspace that is restricted to
gliders. Worst case, users of COTS receivers might have to self impose
that condition or leave, say, a 1,000 ft. buffer

I'm not trying to make trouble but I'm genuinely baffled as to what is
the problem. If GPS altitude is more accurate and COTS receivers are
no more vulnerable to a determined hacker than, say, my Cambridge
Model 20 (which I've had open several times), then why not allow them?
Saying that the casual pilot can easily borrow an expensive Certified
Flight Recorder from a more serious, more affluent club member on
occasion is sort of like prohibiting the sale of affordable cars to
the average citizen on the rationale that he/she can borrow an Audi or
Lexus or Mercedes from a generous neighbor anytime they need to drive
somewhere.

Chip Bearden
ASW 24 "JB"
USA