This is to help fix the tilted horizon issue in the Phantom 3, Phantom 4, Inspire 1, and All DJI Gimbals. 

First do a COLD IMU Calibration. To do this cool down your machine over an A/C vent or or in the fridge. Do not cool the battery. Preform the IMU calibration on a perfectly level surface. If you can use a bubble level to check the surface do so. 

Do a gimbal calibration while on the ground, then let the UAV sit for 2 minutes.

Next calibrate the compass before flight. 

If needed do a gimbal calibration in the air. 


Hope that helps with the tilted horizon issue in your pictures.