Image augmented laser scan matching for indoor dead reckoning

Most existing approaches to indoor localization focus on using either cameras or laser scanners as the primary sensor for pose estimation. In scan matching based localization, finding scan point correspondences across scans is challenging as individual scan points lack unique attributes. In camera based localization, one has to deal with images with few or no visual features as well as scale factor ambiguities to recover absolute distances. In this paper, we develop multimodal approaches for two indoor localization problems by fusing a camera and laser scanners in order to alleviate the drawbacks of each individual modality. For our first problem we recover 3 degrees of freedom (DoF) of a camera-laser rig on a rolling cart in a 2D plane, by using visual odometry to facilitate scan correspondence estimation. We demonstrate this approach to result in a 0.3% loop closure error for a 60 m loop around the interior corridor of a building. In our second problem, we recover 6 DoF of a human operator carrying a backpack system mounted with sensors in 3D, by merging rotation estimates from scan matching and translation estimates from visual odometry, resulting in a 1% loop closure error.