Baro-aiding augments GPS integrity using which source?

• A. Nonsatellite input sources used to augment GPS.
• B. Satellite-only GPS signals.
• C. Nonsatellite input sources used to augment GPS, with the current altimeter setting entered.
• D. Radar data.

Answer: (C)

Baro-aiding relies on nonsatellite information to supplement GPS, specifically using the aircraft’s barometric data with the current altimeter setting entered. This barometric input provides a vertical constraint that complements the GPS solution, helping verify altitude, improve integrity, and speed up convergence of the navigation solution, especially when satellite signals are weak or noisy. The altimeter setting is essential because it ties the barometric altitude to the local atmospheric pressure, aligning the baro-derived height with what the aircraft actually experiences.

Radar data isn’t part of baro-aiding, and satellite-only GPS ignores the cross-check provided by the barometric input. Using nonsatellite inputs without the altimeter setting wouldn’t yield a correct or useful altitude constraint, so including the current altimeter setting is what makes baro-aiding effective.