title: Monocular Vision System for Fixed Altitude Flight of Unmanned Aerial Vehicles.
abstract: The fastest and most economical method of acquiring terrain images is aerial photography. The use of unmanned aerial vehicles (UAVs) has been investigated for this task. However, UAVs present a range of challenges such as flight altitude maintenance. This paper reports a method that combines skyline detection with a stereo vision algorithm to enable the flight altitude of UAVs to be maintained. A monocular camera is mounted on the downside of the aircraft's nose to collect continuous ground images, and the relative altitude is obtained via a stereo vision algorithm from the velocity of the UAV. Image detection is used to obtain terrain images, and to measure the relative altitude from the ground to the UAV. The UAV flight system can be set to fly at a fixed and relatively low altitude to obtain the same resolution of ground images. A forward-looking camera is mounted on the upside of the aircraft's nose. In combination with the skyline detection algorithm, this helps the aircraft to maintain a stable flight pattern. Experimental results show that the proposed system enables UAVs to obtain terrain images at constant resolution, and to detect the relative altitude along the flight path.
authors.affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1040510304@ndu.edu.tw.
authors.forename: Kuo-Lung
authors.initials: KL
authors.lastname: Huang
authors.affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. davidchiu@ndu.edu.tw.
authors.forename: Chung-Cheng
authors.initials: CC
authors.lastname: Chiu
authors.affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. 1030510306@ndu.edu.tw.
authors.forename: Sheng-Yi
authors.initials: SY
authors.lastname: Chiu
authors.affiliation: School of Defense Science, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. c31020410@ndu.edu.tw.
authors.forename: Yao-Jen
authors.initials: YJ
authors.lastname: Teng
authors.affiliation: Department of Electrical and Electronic Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan 33551, Taiwan. shushenghao@gmail.com.
authors.forename: Shu-Sheng
authors.initials: SS
authors.lastname: Hao
keywords: monocular camera; motion vector detection; stereo vision; unmanned aerial vehicle (UAV)