BARLD: Barometer-Assisted Road-Layer Detection

Existing global navigation satellite systems (GNSSs) provide insufficient accuracy in terms of GNSS elevation and are limited by two-dimensional maps. Therefore, when traveling along a road that branches off to an overpass, it is impossible to immediately determine whether the vehicle is on the overpass. Inaccurate navigation not only causes anxiety for some drivers but also can lead to car accidents. This problem has existed since the invention of GNSSs. To the best of our knowledge, we are the first to conduct a large number of on-road experiments at different locations using off-the-shelf smartphones equipped with barometers. Based on the preliminary results of the wind tunnel and on-road experiments, we propose barometer-assisted road-layer detection (BARLD), which uses the changes in atmospheric pressure to determine the relative altitude. Comprehensive experiments in many different scenarios, including on overpasses, underpasses, and in parking lots, are discussed in this paper. The results confirm that the BARLD can effectively assist consumer-grade GNSSs to determine road layers. The source code of BARLD is publicly available, which would benefit the research community.