I have never done the accelerometer calibration, because I do not know how to do it (I read the manual 1.1, but it's not enough). Calibration must be carried out on the ground, before takeoff, to calibrate the altimeter (0 feet where he takes off), or is independent from this ? If I make the calibration at my house, on a table, I am sure that the H is perfectly horizontal, while, at the flying ground, no. Can you tell me what is the right way to do the accelerometer calibration? Thanks in advance for any response.