re: #76 O say, does that Star Spangled Banner yet wave..

I was going to say, 20 years ago when we were doing high-altitude research balloons as test flights of our satellite program at our university (testing the data link radios and control/telemetry software), we had no problems with recording altitudes upwards of 70,000 feet.

You could use an ITAR-restricted GPS receiver, if you filed the proper paperwork with the State Department and paid the right fees (and were US-based, otherwise there’s much more paperwork). It’s a question of knowing that that would be an issue.