Small errors in the measurements of the inertial sensors can be compounded over time, causing drift and leading to inaccuracies in the calculated position, velocity and attitude. In order to improve the accuracy of the system, an INS can be combined with a GNSS receiver, which outputs its own position and velocity information.
A GNSS-INS uses advanced Kalman filtering estimation techniques to combine measurements from the two sources, improving the accuracy of position, velocity and attitude.
Both sources have distinct advantages – while the GNSS receiver helps correct inaccuracies in the inertial system measurements, the inertial navigation system provides better dynamic performance than a standalone GNSS receiver, and also provides continued navigation capabilities in the event of a GPS or GNSS outage. This makes GNSS-aided inertial guidance systems particularly useful for drones, UAVs and robotic vehicles, that may have to navigate in heavy woodland, urban canyons, tunnels and other GNSS-denied environments.
GNSS-INS may have one or two GNSS receivers. Dual GNSS-INS are also known as GNSS Compass/INS. The GNSS compassing technique fuses measurements from the two separate receivers to provide a more accurate estimate of the system’s heading.
GNSS compassing uses a form of real-time kinematic positioning (RTK) to determine heading. The two receiver antennas must be rigidly mounted with a known fixed distance, or baseline, between them. The antennas also require a clear view of the sky and excellent satellite signal conditions.
Embedded GPS inertial navigation systems and RTK correction capabilities are crucial to BVLOS drone applications and flights subject to weak GNSS signals due to environmental features such as tunnels or heavily built up areas.
Drones and UAVs with integrated GNSS inertial sensors are used within commercial, industrial and tactical applications such as aerial mapping and survey, autonomous agriculture and environmental monitoring, pipeline inspection, intelligence, surveillance & reconnaissance (ISR), search and rescue (SAR) operations.