Attitude-Guided Loop Closure for Cameras with Negative Plane

Loop closure is an important component of Simultaneous Localization and Mapping (SLAM) systems. Large Field-of-View (FoV) cameras have received extensive attention in the SLAM field as they can exploit more surrounding features on the panoramic image. In large-FoV VIO, for incorporating the informative cues located on the negative plane of the panoramic lens, image features are represented by a three-dimensional vector with a unit length. While the panoramic FoV is seemingly advantageous for loop closure, the benefits cannot easily be materialized under large-attitude-angle differences, where loop-closure frames can hardly be matched by existing methods. In this work, to fully unleash the potential of ultra-wide FoV, we propose to leverage the attitude information of a VIO system to guide the feature point detection of the loop closure. As loop closure on wide-FoV panoramic data further comes with a large number of outliers, traditional outlier rejection methods are not directly applicable. To tackle this issue, we propose a loop closure framework with a new outlier rejection method based on the unit length representation, to improve the accuracy of LF-VIO. On the public PALVIO dataset, a comprehensive set of experiments is carried out and the proposed LF-VIO-Loop outperforms state-of-the-art visual-inertial-odometry methods. Our code will be open-sourced at https://github.com/flysoaryun/LF-VIO-Loop.