What is Atti and GPS Mode?

Hi, thanks for the inquiry. I would like to clarify if you're referring to the flight mode of the Phantom 4? If so, the P-mode, works when the GPS signal in the environment is strong allowing the aircraft to fly at stable condition and also it would allow you to use the Intelligent flight modes feature. It's recommended flying your drone with this mode for you to maximize the usage of your unit. On the other hand, the ATTI mode means that the GPS or Obstacle System is not available. You may refer to the link below for further details. Please let us know if you have other concerns. Thank you for your support.