Tricopter position-hold via webcam + target tracking

I managed to make my Tricopter hover autonomously. A webcam films the copter from below and tracks some LEDs. I calculate x & y position/ velocity/ acceleration, as well as height, vertical velocity and yaw in Matlab.
Data is then transferred via RS232. The goal was to make the copter hover in the centre of the FOV of the camera. The control loops can still be improved a lot I think.
Some more info in the movie...