ISPRS-Archives The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ISPRS-Archives Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci. 2194-9034 Copernicus Publications Göttingen, Germany 10.5194/isprsarchives-XL-1-W4-263-2015 HEIGHT GRADIENT APPROACH FOR OCCLUSION DETECTION IN UAV IMAGERY Oliveira H. C. 1 Habib A. F. 2 Dal Poz A. P. 3 Galo M. 3 São Paulo State University, Graduate Program in Cartographic Sciences, Presidente Prudente, Brazil Purdue University, Lyles School of Civil Engineering, West Lafayette, Indiana, USA São Paulo State University, Dept. of Cartography, Presidente Prudente, Brazil 26 08 2015 XL-1/W4 263 268 Copyright: © 2015 H. C. Oliveira et al. 2015 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://isprs-archives.copernicus.org/articles/XL-1-W4/263/2015/isprs-archives-XL-1-W4-263-2015.html The full text article is available as a PDF file from https://isprs-archives.copernicus.org/articles/XL-1-W4/263/2015/isprs-archives-XL-1-W4-263-2015.pdf

The use of Unmanned Aerial Vehicle (UAV) significantly increased in the last years. It is used for several different applications, such as mapping, publicity, security, natural disasters assistance, environmental monitoring, 3D building model generation, cadastral survey, etc. The imagery obtained by this kind of system has a great potential. To use these images in true orthophoto generation projects related to urban scenes or areas where buildings are present, it is important to consider the occlusion caused by surface height variation, platform attitude, and perspective projection. Occlusions in UAV imagery are usually larger than in conventional airborne dataset due to the low-altitude and excessive change in orientation due to the low-weight and wind effects during the flight mission. Therefore, this paper presents a method for occlusion detection together with some obtained results for images acquired by a UAV platform. The proposed method shows potential in occlusion detection and true orthophoto generation.