"Jay Beckman" writes:

How do you measure altitude at 328k feet? Surely a standard
barometric device isn't going to work?

Ground based radar? Inertial telemetry? GPS?

Regardless, they'd better make damn sure that they get it right
otherwise someone is likely to run around telling the crowd how
long "to impact"...
http://www.avweb.com/newswire/10_24b.../187440-1.html

(Also...how does "inertial telemetery" determine altitude?!)

--kyler