On my first waypoints mission my phantom flew below the altitude of the home point and did not seem to even approach the altitude that the waypoint was set at. My first question is: how do these phantoms calculate their altitude? I know they have barometers but do they not also work in relevance to the homepoint? I'm using the latest firmware and flying the P3P with an ipad mini 2 with cell. I have read here DJI Forum|Waypoint Mission loses altitude on 2nd pass. about altitude variance and I would post this on the DJI forum except I can't because I never recieve the confirmation email. So, I took off from ground level (obviously) and then flew out in front of the house to set the fist waypoint at 11m alt, and then threw in 2 more waypoints and engaged waypoints. The phantom returned to the first waypoint but plummeted to below ground level from where I was standing (the ground slopes away in front of the house) and was well below actual 11m from the grass when I flicked it back to P mode and safely returned to home. If it was using the home-point as a reference for altitude I can't see how it did this through recalculation. I will be trying again as soon as my nerves have settled and will work at a much higher altitude at first (although for the sort of cinematography i do I need to be flying at relatively low alt. Is anybody else seeing these sorts of errors and understands their cause?? Many thanks.