Extened Kalman filter based on https://en.wikipedia.org/wiki/Extended_Kalman_filter Designed to merge only IMU and OptiTrack/VICON (no baro, sonar, GPS, ...) - predict attitude and path with gyroscopes and accelerometers - correct attitude and path with external pose and position message - estimate gyro and accelerometer biases Bypassed when simulating. @gps,@datalink,@imu ahrs,ins