Satellite navigation is limited to approximately +/- 2 meters accuracy (without the benefit of a DGPS ground station). Even with a 20 Hz update rate, that's too

Satellite navigation is limited to approximately +/- 2 meters accuracy (without the benefit of a DGPS ground station). Even with a 20 Hz update rate, that's too much for IMU dead reckoning to compensate for. It's simply not good enough for navigating at anything but large scale. Fully autonomous model aircraft will need to use simultaneous localization and mapping (LIDAR or depth cameras) in order to do anything interesting. Right now that hardware is heavy and the processing power needed to do it in real time is significant. Maybe some day you'll be able to install an app on your quadrotor and have it follow you around like a dog, but right now that's not realistic.