IMU calibration instruction has been varied. Most agree that only do it when prompted to, or when you have a problem that IMU calibration can fix. The HOW part is equally varied. The official DJI instruction vid says to dismount the props, yet the video is done with the props on. Notable gurus on this forum have even said that when you do calibrate, do so on a perfectly level surface, verified with a carpenters level even. The thing that is confusing, is that DJI says it can be done with props on OR off. But there is a difference in the Mavic orientation with the props on vs. off. If absolute level is important, than so to must be the prop placement. If it is not critical, then maybe the calibration is just relative to the Mavic itself, and not so much as the surface it's on (other than it be flat). I have had great success calibrating with props on, and others have had equal success with them off. It seems to not matter, nor does an absolute level surface then. Any thoughts?