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Comment by jlgreco | Hacker News Reader

Consumer GPS devices do not work above 18 km, so unfortunately even without the cell reception limitations he would not have been able to track the balloon during it's entire voyage. (They also don't work when travelling faster than 1000 mph. I believe the limitations are to prevent consumer GPS hardware from being used in things like missiles.)

I hope he manages to recover everything alright.

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Yes, that was what I was thinking, over altitude, GPS shuts off. Also I was wondering if freezing the crap out of the batteries might affect their overall charge capacity.

Reading the antics of the folks over that theregister.co.uk and their high altitude experiments (granted its mostly a lot of puns around LOHAN) what struck me was they proceed very methodically in their planning. A reasonable guide for anyone wanted to get into the space balloon business I think.

Are these COCOM limitations based in the hardware or software of the GPS devices by the manufacturers? If it's in the software, are there not free and opensource firmwares out there that can go around such limitations?

The GPS receiver doesn't shutoff. The requirement is to stop tracking.

There are some manufacturers that take those limits to be over 60K feet AND the mph limit. Others assume it to be OR.

Spark Fun sells GPS modules which can be programmed, and interfaced with telemetry systems that send data back over radio so you can get it the entire time.

They talk about GPS devices being "altitude safe". That seems to mean they work over 60K.

It's actually 1000 knots (1200 mph). https://en.wikipedia.org/wiki/CoCom#Legacy

It's supposed to be 1000 knots when above 60k ft. Due to laziness/cost, many GPS modules take it to mean any speed above 60k feet. Here's a list of ones that will work above 60k feet:

http://showcase.netins.net/web/wallio/GPSrcvrsvs60kft.htm

Ah yes, good catch. I knew it was something like that; I always forget knots are not mph.

Interesting. I've always been curious if there were limits on what these things would register. I had a speedometer app on my phone and I remember it registering about 460 mph on one of my flights.

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