  In this paper, a simple technique for Unmanned Aerial Vehicles (UAVs)
potential landing site detection using terrain information through
identification of flat areas, is presented. The algorithm utilizes digital
elevation models (DEM) that represent the height distribution of an area. Flat
areas which constitute appropriate landing zones for UAVs in normal or
emergency situations result by thresholding the image gradient magnitude of the
digital surface model (DSM). The proposed technique also uses connected
components evaluation on the thresholded gradient image in order to discover
connected regions of sufficient size for landing. Moreover, man-made structures
and vegetation areas are detected and excluded from the potential landing
sites. Quantitative performance evaluation of the proposed landing site
detection algorithm in a number of areas on real world and synthetic datasets,
accompanied by a comparison with a state-of-the-art algorithm, proves its
efficiency and superiority.
