To achieve the landing site locating, the proof-of-concept strategy demands a reference image captured beforehand. This strategy adopts the way of wide-baseline matching between images from the airborne camera and the reference image. First of all, a proof-of-concept strategy of vision-aided landing area locating of unmanned aerial vehicle is presented. Then, there are mainly two algorithms under discussion. One is landing site finding using SIFT based wide-baseline
match, and the experiment results show that is qualified to finding landing site. The other is landing site locating by camera position measurement based on the feature point with known world coordinates. Assuming that the airborne camera has been calibrated off-line, with known intrinsic camera parameters and world coordinates of at least 4 feature points, the position of camera can be roughly estimated. The SIFT feature points of reference image have been selected
and their position in world coordination have been marked before wide-baseline matching, so, when matching having been put into practice, world coordinates of matched points in each image captured by airborne camera can be gotten directly. Assuming when landing site locating task is carrying out, the UAV is fairly high, so the landing site could be regarded as planar. And due to the camera is fixed to UAV, the relative position of UAV to the landing site can be measured according the algorithm in this paper, that is to say, providing that at least one image of UAV landing site is offered, the landing site can be successfully located.