I am currently working on a NASA-backed High Altitude Weather Balloon project and I was curious if there was as script that would allow for a canon to start taking pictures based on it's GPS coordinates or a script that would allow a gps module to tell the camera to start taking a rapid series of pictures when you reach this height?
If you are using an external flight computer (could be an arduino etc), than you could start a script using the
USB Remote or
PTP Extension. Or if you control the power with it, just use a startup script and power on the camera when you reach the desired altitude.
If you want to use a camera with a built-in GPS, I think you could do this using the GPS propcase. You would need to write the script yourself, or find someone to write it. Look at core/gps.c in the CHDK source for how this is used.
If you just want to start at some approximate altitude, some kind of pressure switch connected the USB remote might be a simpler approach.