What is velocity-aiding in INS/GNSS fusion?

• A. Using GNSS-derived velocity to improve INS velocity estimates and/or update the filter.
• B. Using INS-derived altitude to adjust GNSS clock.
• C. Using GNSS to estimate magnetic field.
• D. Discarding velocity data to save energy.

Answer: (D)

Velocity-aiding means using GNSS-derived velocity measurements to constrain and correct the INS velocity estimate within the fusion filter. The INS tends to drift over time as biases and noise accumulate, so feeding the filter with GNSS velocity (typically from Doppler measurements or GNSS-based velocity) provides an absolute reference for how fast the platform is actually moving. The filter compares the GNSS velocity with the INS-predicted velocity and applies an update to the velocity state (and related biases if modeled) to keep the navigation solution aligned with the GNSS data. This reduces drift and improves accuracy, especially between GNSS updates or when short-term velocity fidelity is crucial.

This concept is distinct from adjusting the GNSS clock with INS-derived altitude, estimating magnetic fields from GNSS data, or discarding velocity data to save energy, which do not constitute velocity-aiding.