Abstract: A method for autonomously tracking a landing surface by a UAV to enable repeated autonomous take off and landings without the need for GPS data or any other satellite positioning techniques. The landing surface may be on an autonomous and/or moving ground vehicle, and comprises two or more markers on the landing surface. The markers may be of different sizes. The drone comprises two or more downward looking cameras, with at least one camera having a different focal length to the other, to form a dual monocular system which captures images of the markers on the landing surface. The images are analysed to estimate the pose of the markers and thus determine the location of the UAV with respect to the landing surface, which is then provided to a flight controller of the UAV.