GPS and IMU Require Visual Odometry for Elevation Accuracy

Currently, self-localization of vehicles is primarily carried out by GPS receivers of different price and performance classes, which are permanently installed in vehicles. Known limitations of GPS-based localization include signal disturbances due to multipath propagation, as it may occur in narrow street canyons or tree alleys, as well as signal losses in tunnels or entrances to buildings, for example. It may happen that horizontal GPS channels still support a useful 2D positioning with low uncertainties while the GPS altitude channel has very large deviations or error uncertainties. Additional sensors (IMU or cameras) help to detect sections of trajectories where the GPS signal becomes unusable. Based on a traditional navigation strategy (i.e. integration of IMU and GPS), we also study the possible integration of visual odometry obtained from a stereo camera system. The paper reports about a large-scale project studying multi-sensor integration for very accurate and robust self-localization of vehicles.