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Journal of Robotics
Volume 2009, Article ID 854102, 16 pages
http://dx.doi.org/10.1155/2009/854102
Research Article

Exploiting Attitude Sensing in Vision-Based Navigation for an Airship

Institute of Systems and Robotics, University of Coimbra, Pólo II, 3030 Coimbra, Portugal

Received 28 November 2008; Revised 14 March 2009; Accepted 23 June 2009

Academic Editor: Giovanni Muscato

Copyright © 2009 Luiz G. B. Mirisola and Jorge Dias. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An Attitude Heading Reference System (AHRS) is used to compensate for rotational motion, facilitating vision-based navigation above smooth terrain by generating virtual images to simulate pure translation movement. The AHRS combines inertial and earth field magnetic sensors to provide absolute orientation measurements, and our recently developed calibration routine determines the rotation between the frames of reference of the AHRS and the monocular camera. In this way, the rotation is compensated, and the remaining translational motion is recovered by directly finding a rigid transformation to register corresponding scene coordinates. With a horizontal ground plane, the pure translation model performs more accurately than image-only approaches, and this is evidenced by recovering the trajectory of our airship UAV and comparing with GPS data. Visual odometry is also fused with the GPS, and ground plane maps are generated from the estimated vehicle poses and used to evaluate the results. Finally, loop closure is detected by looking for a previous image of the same area, and an open source SLAM package based in 3D graph optimization is employed to correct the visual odometry drift. The accuracy of the height estimation is also evaluated against ground truth in a controlled environment.