What is a key benefit of integrating barometric altitude with GNSS/INS beyond redundancy?

• A. Barometric altitude provides complementary vertical reference; it helps detect vertical GNSS anomalies and can constrain vertical drift.
• B. Barometric altitude only affects horizontal accuracy.
• C. Barometric altitude cannot be used with GNSS/INS.
• D. Barometric altitude is more precise than GNSS.

Answer: (A)

The key idea is that barometric altitude provides an independent vertical reference that complements GNSS/INS, not just a backup. A barometer measures height based on atmospheric pressure, which is a different physical signal than GNSS height. When you fuse this with the GNSS/INS solution, the vertical state gets an additional, constraint-based measurement, which reduces vertical drift in the INS between GNSS updates.

This integration also helps reveal vertical inconsistencies: if the GNSS-derived height disagrees with the barometric height, the system can flag a potential vertical anomaly or GNSS error (like multipath or clock bias affecting altitude). While weather can slowly bias the barometer, its short-term measurements still provide a stable reference that improves vertical accuracy and robustness of the overall solution, especially during GNSS outages or poor satellite geometry.