".Blueskies." wrote in message
t...
What about GPS precision approaches...where does the glideslope
information come from?


WAAS?

WAAS is insufficient for a precision GPS approach. GPS precision approaches
use "LAAS", which is basically the same as WAAS except that the differential
station is much closer to the airport (I suppose in some or many cases it
may even be colocated...not sure). It's "local area" instead of "wide
area".

WAAS and LAAS are both a form of differential GPS, and it's true that both
increase the accuracy of GPS significantly, LAAS more so than WAAS.
However, a) Jim never restricted his claim to GPS using WAAS, and b) even
with WAAS (or LAAS, for that matter), the GPS does not indicate the same
altitude that a properly set altimeter would.

Pete