A strange question to ask but here it is: At what altitude will the gps system no longer work? My idea is to send a balloon into space with a smartphone. I have a feeling it will only fail if the phone freezes. What do the experts say?
This is not an authoritative answer, but the GPS receiver should work without regard to altitude. As far as temperature goes, it's hard to say. The battery might be affected by temperature more than anything else, but at extremely low temperature, only testing will tell.
I won't actually interact with the phone. I want to send the gps info to a server running sql. If the data connection is lost, I will save the data on a SD card and hope that I get the phone back when it plummets back to earth!
Having read a bit in internet about this, as far as I can find:
Standard GPS (not military grade) should work up to about 8 km, then it dies but comes back again when it is lower than 8 km. This should help finding the thing again.
@Erel, thanks for the thought. SMS would also be an option but it would have to be an MMS as I will activate the camera as well.