Here is source code for various languages that you may find useful in developing high altitude things.

• Bash script to rotate and GZIP log files
• GPS emulator
• octave datalogger code
• kml near realtime update
• Reed-Solomon encoder
• NMEA collection
• dxlog - logs truetty output directly to file (standard logging has a delay)
• 4 state extended kalman filter in matlab

• Navigation
• SSTV
• Floating point print function
• Sqrt density lookup table calculator (for fast drag coefficient calculations)

• Interrupt driven TSIP parser for AVR
• Interrupt driven NMEA parser for AVR
• AVR radio pulse shaper code
• I2C EEPROM

• Camera shutter trigger
• Arduino GPS RS-232 Reader

• Two state Kalman Filter for parafoils and Rogallos
• Optimised two state heading filtering Kalman filter
• Guidance and navigation for parafoils and Rogallos
• PWM filtering and switching for UAV control