This paper presents concepts and some experiment on UAV automatic landing on any flat area without prior knowledge of (detachable) markers' positions. The process consists of two key notions. First, the UAV approximates 3D positions of four color markers using a single camera stereoscopic scheme. In other words, the aircraft flies and captures images of ground to create depth map of the four markers. Second, it relies on a pose estimation algorithm (here, Homography) to approximate rotational and, especially, translational information between air to ground. What is novel in this concept is z-coordinate of markers on ground can always be normalized based on our kinematic chain. Thus, homography can be used. Additionally, depth estimation using stereo vision with a camera is shown in experimental result. Furthermore, the whole process is also possible without GPS data, which might post problem in some certain situations, e.g. inadequate positioning accuracy for small landing area, or unreliability during warfare.
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