Geopositioning and Navigation

The Geopositioning and Navigation research group are working with Global Navigation Satellite Systems and other navigation sensors. Our research focus on the errors and disturbances of GNSS signals caused by space weather-induced ionospheric disturbances, tropospheric refraction, multipath and radio-frequency interference, such as jamming or spoofing.

The group also focuses on improving positioning and navigation for robots and unmanned aerial vehicles (UAVs) to enable new remote sensing technologies and to support green transition and smart cities. A key aspect of this is developing robust navigation systems with multiple sensing technologies, such as GNSS, inertial navigation, radar, visual odometry / simultaneous localization and mapping (SLAM) and LiDAR Odometry and Mapping (LOAM). Within the UAWOS project, the group focuses on the development of beyond visual light of sight (BVLOS) support systems for UAVs performing hydrological surveys in rivers. This includes the development of obstacle detection, autonomous flight and sensor fusion algorithms, to ensure safe operation and robust localization of the survey drone.

The group operates several state-of-the-art GNSS reference station networks, including the Testbed in Aarhus for Precise Positioning and Autonomous Systems (TAPAS). The TAPAS Real Time Kinematic (RTK) network consists of 11 GNSS reference stations within the municipality of Aarhus and is being used to provide GNSS users position accuracies better than 1 cm in real-time. The group is also co-responsible for the SWADO network (together with the Geomagnetism department), with the purpose of monitoring space-weather effects in the Arctic (Greenland and Faroese Islands) and designing a system for providing warnings to GNSS users when the use of GNSS is impaired due to  ionospheric scintillations. The Danish National Galileo Overlay (DANGO) project aims to speed up the use of Galileo PNT services by using national GNSS support. It involves converting positions from the Galileo Terrestrial Reference Frame to Denmark's national reference frame, ensuring quick user access to Galileo HAS, updating DANGO services in real-time, and monitoring both Galileo and DANGO services in real-time.

GNSS signals are susceptible to ground-based signals interfering, i.e., jamming, by virtue of the small power needed from nearby transmissions to exceed the power received from a given GNSS satellite. Such jamming hinders the effective use of GNSS for both positioning and timing. Array-based receivers can both mitigate the impact and locate the source of disturbances as well, enabling mission critical position. The group also investigates the use of such receiver arrays based on digital hardware, namely Software-Defined Radio (SDR), developing methodology for tasks of mitigation and localization and undertaking measurement campaigns.