This device was created in a hurry for the USC Rocket Propulsion Lab, the student-run high-altitude rocketry effort at USC. I think I soldered it together a day or two before the launch, and then programmed it on a laptop on the car trip out to the desert. It uses a Picaxe 18X microcontroller and accepts a GPS NMEA data stream at 4800 baud (I think?). It pulls out the altitude and logs it to a 24LC512 external EEPROM, and then reads it back when you are done.

Here is a full schematic for it:

I unfortunately do not have any pictures of the board, but it was pretty simple. Here is the source code.

And the best part, here is a picture of the rocket lifting off:

For scale, the rocket is about 15 feet tall. It’s made of carbon-fiber, and was hand-built by our team. We even made the motors for it!

The GPS logger worked perfectly, as you can see from this nifty chart I was able to get out of it:

You can clearly see where the GPS device briefly lost satellite lock on the way down. The rocket hit a final altitude of about 18,400 feet! Its take-off was also the single loudest thing I have ever heard in my life. If you ever get a chance to watch a large rocket launch, I highly recommend it!