1. A method for navigating a UAV, the method comprising: piloting the UAV, under control of a navigation computer, in accordance with a navigation algorithm; while piloting the UAV: reading from a GPS receiver a sequence of GPS data; anticipating a future position of the UAV in dependence upon the sequence of GPS data; identifying an obstacle in dependence upon the future position; selecting an obstacle avoidance algorithm; and piloting the UAV in accordance with the selected obstacle avoidance algorithm.