How does barometric altitude complement GNSS/INS for vertical navigation robustness?

How does barometric altitude complement GNSS/INS for vertical navigation robustness?

• A. Barometric altitude provides a complementary vertical reference; it helps detect vertical GNSS anomalies and can constrain vertical drift when integrated with GNSS/INS.
• B. Barometric altitude replaces GNSS in vertical positioning.
• C. Barometric altitude has no impact on vertical robustness and should be ignored.
• D. Barometric altitude can introduce large errors and degrade vertical estimates.

Answer: (A)

Barometric altitude provides an independent vertical reference that complements GNSS/INS by adding a second source of information about height. In many GNSS/INS setups, the vertical component is less well observed than the horizontal, and the INS tends to drift in the vertical due to sensor biases. A barometer offers a near-continuous altitude measurement derived from atmospheric pressure, which is not tied to GNSS or INS error sources. When this pressure-based altitude is fused with GNSS and inertial data, it constrains the vertical state, reducing drift and helping maintain accurate altitude even if GNSS signals become degraded or briefly unavailable. This setup also helps flag vertical GNSS anomalies. If the GNSS-derived altitude suddenly disagrees with the barometric measurement, the system can detect a potential issue in the GNSS solution and rely more on the barometer while keeping the vertical estimate robust. Of course, the barometer has its own challenges—pressure changes due to weather and local terrain, and potential biases—that must be modeled and estimated within the fusion algorithm. When handled properly, the combination enhances vertical robustness more than GNSS/INS alone.

Barometric altitude provides an independent vertical reference that complements GNSS/INS by adding a second source of information about height. In many GNSS/INS setups, the vertical component is less well observed than the horizontal, and the INS tends to drift in the vertical due to sensor biases. A barometer offers a near-continuous altitude measurement derived from atmospheric pressure, which is not tied to GNSS or INS error sources. When this pressure-based altitude is fused with GNSS and inertial data, it constrains the vertical state, reducing drift and helping maintain accurate altitude even if GNSS signals become degraded or briefly unavailable.

This setup also helps flag vertical GNSS anomalies. If the GNSS-derived altitude suddenly disagrees with the barometric measurement, the system can detect a potential issue in the GNSS solution and rely more on the barometer while keeping the vertical estimate robust. Of course, the barometer has its own challenges—pressure changes due to weather and local terrain, and potential biases—that must be modeled and estimated within the fusion algorithm. When handled properly, the combination enhances vertical robustness more than GNSS/INS alone.