Using AsteRxi GNSS/MEMS IMU receiver in a container positioning system

High-end GNSS receivers are deployed in rapidly increasing numbers in industrial applications. Their challenging operational environment exposes the vulnerability of GNSS technology. For example, container terminal operators in harbors are increasingly using GNSS positioning for their container positioning systems. The primary goal of using GNSS in such an application is to reduce the amount of lost containers for economical and safety reasons. Therefore, it is important to track each container in a reliable and accurate manner. While this is typically not an issue for the positioning of containers on the yard for professional GNSS receivers due to open-sky conditions, problems arise below cranes and in the vicinity of ship hulls. At these locations, a GNSS-only position solution is insufficient due to the large metal surfaces which cause low measurement availability and increase the possibility that signals are tracked via indirect paths. To mitigate the impact of the operational environment on the position quality and availability, GNSS receivers are traditionally integrated with high-grade IMU systems. This solution, however, remains too expensive for many industrial applications. Septentrio has developed AsteRxi, an integrated GNSS/IMU receiver based on the high-end AsteRx GNSS receiver and the MTi MEMS-based IMU of XSens. In this paper, we prove that combining modern MEMS-based IMU sensors with high-end GNSS receivers provides a cost-efficient solution that satisfies the accuracy, reliability and availability requirements needed for a container positioning system. This paper describes the usage of AsteRxi in container positioning systems based on a test campaign at the harbor of Antwerp. It shows the added value of a high-end receiver in demanding environments, characterized by severe multipath and signal blockage. Addition of a MEMS-based inertial sensor is required to remove effects of uncorrected and undetected meter-level multipath-induced positioning errors, particularly intensive in the ship-loading area. This allows full end-to-end traceability of containers from the cranes on the quay to their storage positions on the yard. The presented results show that in these demanding environments reliable sub-meter positioning is possible using high-end GNSS/MEMS-based IMU integration.