Gakne, Paul VerlaineO'Keefe, Kyle P.G.2018-04-182018-04-182018-04-17Gakne, P. V., & O’Keefe, K. P. G. (2018). Tightly-Coupled GNSS/Vision Using a Sky-Pointing Camera for Vehicle Navigation in Urban Areas. "Sensors," 18(4), 1–32. https://doi.org/10.3390/s180412441424-8220http://hdl.handle.net/1880/111486https://dx.doi.org/10.11575/PRISM/37444This paper presents a method of fusing the ego-motion of a robot or a land vehicle estimated from an upward-facing camera with Global Navigation Satellite System (GNSS) signals for navigation purposes in urban environments. A sky-pointing camera is mounted on the top of a car and synchronized with a GNSS receiver. The advantages of this configuration are two-fold: firstly, for the GNSS signals, the upward-facing camera will be used to classify the acquired images into sky and non-sky (also known as segmentation). A satellite falling into the non-sky areas (e.g., buildings, trees) will be rejected and not considered for the final position solution computation. Secondly, the sky-pointing camera (with a field of view of about 90 degrees) is helpful for urban area ego-motion estimation in the sense that it does not see most of the moving objects (e.g., pedestrians, cars) and thus is able to estimate the ego-motion with fewer outliers than is typical with a forward-facing camera. The GNSS and visual information systems are tightly-coupled in a Kalman filter for the final position solution. Experimental results demonstrate the ability of the system to provide satisfactory navigation solutions and better accuracy than the GNSS-only and the loosely-coupled GNSS/vision, 20 percent and 82 percent (in the worst case) respectively, in a deep urban canyon, even in conditions with fewer than four GNSS satellites.en©2018 by the authors.visual odometryupward-facing cameramotion estimationsatellitesGNSStightly-coupled integrationvehicle navigationimage segmentationclustering algorithmspublishedVersionhttp://dx.doi.org/10.3390/s18041244