Multipath Mitigation using Omnidirectional Infrared Camera for Tightly Coupled GPS/INS Integration in Urban Environments

This paper describes a precision positioning technique that can be applied to vehicles or mobile robots in urban environments. Currently, the availability of satellite positioning is anticipated to improve because of the presence of various positioning satellites such as U.S.'s GPS, Russia's GLONASS and Europe's GALILEO systems. However, because of the serious impact of multipath on their positioning accuracy in urban areas, such improvements in the availability of satellite positioning do not necessarily also facilitate high precision positioning. In this study, we propose a precision positioning technique that can be applied to vehicles or mobile robots in urban environment using a single frequency GNSS receiver, and we propose a technique to realize code multipath mitigation that uses an omnidirectional IR (infrared) camera to exclude invisible satellites. With the IR camera, the sky is distinctively dark. This makes it easy to detect the borderline between the sky and the obstacles such as the buildings, which are captured in white, due to the difference in the atmospheric transmittance rates between visible light and far-IR rays. Moreover we apply a tightly coupled GPS/INS (inertial navigation system) integration based on code and carrier phase from visible satellites determined by the omnidirectional IR camera. In a situation of degraded GNSS availability because of elimination of invisible satellites however a tightly coupled configuration is capable of updating the filter with only one visible satellite. Positioning evaluation was carried out only with visible satellites that have less multipath errors and without using invisible satellites. The evaluation results confirm the effectiveness of the proposed technique and the feasibility of its highly accurate positioning.