The drift rate on internal gyros has been reduced since the first generation Pixhawk and the extended Kalman filter has been improved. How has this effected the ability of a plane to follow routes? How often does it need GPS in order to keep flying in the general direction? If a plane thinks it has passed through several waypoints, and then GPS kicks in, does it just null out the systematic error and then proceed to the next waypoint? I am designing a long range flight with companion computer to turn off GPS at various intervals long the flight route so as to better understand these issues. If anyone has already done this, please post the results. If not, please post your predictions.