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
• dxlog - logs truetty output directly to file (standard logging has a delay)
• UK Polygon - for cutdowns
• Geofence Descriptions - Geofences for Territorial Waters

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

• I2C ublox 5 demonstration code using the UBX protocol
• Interrupt driven UBX parser for AVR
• Interrupt driven TSIP parser for AVR
• Interrupt driven NMEA parser for AVR
• AVR radio pulse shaper code
• I2C EEPROM
• AD7746 Capacitive sensor interfacing demo code

• 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
• Ground data display with php

• Extended Kalman filter (EKF) using quaternion as the state vector
• EKF with gyro bias tracking and quaternion
• Octave/Matlab implementation based on the diydrones.com algorithm
• ascii data from Sparkfun 6DOF IMU
• C code for automatic bias and gain claibration of an accelerometer or magnetometer from 6 attitudes
• Accel/Magno gain and bias calibration