Jay Honeck wrote in message ...
How accurate is GPS for determining altitude, now that WAAS is active?

I was in the air over five hours yesterday, and while droning along found
that our new AvMap's altitude readout was just about dead-nuts accurate --
it was maybe 50 feet off, at times.

In fact, due to the constantly changing barometric pressure along our route
of flight, there were times when I might have trusted it before my
altimeter.

Anyone know how precise it is now?
--

Jay, The FAA seems to say 3 meters vertical throughout the majority of the
continental U.S. and portions of Alaska:

http://gps.faa.gov/Programs/WAAS/waas.htm


But the site below says 6 meters (95 percent of the time) with a worst case
of 15.7 meters.

http://users.erols.com/dlwilson/gpswaas.htm



Here are some more interesting sites:

http://waas.stanford.edu/old_metrics.html

http://waas.stanford.edu/

http://www.edu-observatory.org/gps/dgps.html#WAAS