ANALYSIS OF THE PERFORMANCE OF A LOW-COST V-SLAM DEVICE IN GNSS-DENIED ENVIRONMENT

GNSS (Global Navigation Satellite Systems) are currently the most widespread devices for providing PVT (Position, Velocity and Time), in a wide range of applications, including air and maritime navigation, personal localization and surveying. Such devices are able to provide performance from few meters to few millimetres order, according to the adopted processing technique. One of the most critical drawbacks of GNSS is related to possible discontinuity of the service. For instance, GNSS performance are strictly dependent on the operational scenario, because its working is based on the clean reception of signals transmitted by artificial satellites; therefore, in urban environments or in high vegetation areas, several signals are blocked or are distorted by the presence of obstacles along the propagation, degrading the GNSS solution. The extreme consequence is the interruption of the service, that is the unavailability of the PVT solution. Another critical situation for GNSS is the presence of jamming, an intentional and unintentional interference for signals, which could shut down the service for a certain time. In applications like maritime and air navigation, positioning service interruptions are not acceptable and suitable countermeasures must be taken. The integration with heterogeneous navigation sensors could be a successful approach to fill the GNSS gaps. In this work, V-SLAM (Visual - Simultaneous Localization and Mapping) technique is investigated for supporting GNSS in case of its outages. SLAM technique consists in equipping a mobile to localize with sensors; the measurements from such sensors are exploited to create and update a map of the environment, and simultaneously localizing the mobile itself within the created map. In V-SLAM, visual sensors, such as optical cameras, are used. The performance of standalone V-SLAM technique with a low-cost device are tested in a GNSS-degraded environment such as an urban scenario and the benefits of the combined use of GNSS and V-SLAM are considered too. The results obtained in these conditions can be extended in other contexts such as maritime navigation in the ports or inland navigation.