My Phantom 4 Pro crashed while on a Dronedeploy mission last week. I was mapping an apartment complex and flying low to capture roof damage. The highest point of the roof is about 40’. I set the altitude to 60’ but twice in the mission it lost more than 10’ of altitude.
At point A it was at 47.9’
At point H it crashed into a tree at 43.6’
The battery was at 29% when the crash occurred and I’m pretty sure that all firmware was up to date. Any idea what may have caused this?
All though the our DJI drones are pretty good at maintaining altitude there is still a chance that barometric pressure can change with wind speed and GPS signal is only so accurate. So at times altitude can swing. Another thing that can cause altitude to swing is forward flight. If it happens consistently try testing your phantom to see if it swings in altitude during normal manual flying. If you feel that it is not normal try restarting the phantom and see if it improves.
I have also read some forum posts that the P4 is having issues with losing altitude when stopping. I wonder if the issue you are having is related.
Also on a side note. Remember that shit happens. Drone Deploy can fail. Something can happen with the navigation systems in the phantom. Flying below tree level is risky and quite frankly careless. The resolution of the camera on the P4 should give you plenty of detail to work with at above tree level. Protect your investment, other people and property. Fly above obstacles.