Ground-Corrected Barometric Vertical Navigation System for Vertiport Operations

The vertical separation of air vehicles from the ground, obstacles and other air space participants is critical for safe urban air mobility (UAM) flight operations. In particular, the reliable computation of vertical position plays a key role during take-offs and landings at vertiports for future air taxis. In this work, we investigate and design a barometric system for altitude determination. The system consists of an airborne barometer and a ground station transmitting pressure and temperature to the air vehicle. The system is designed to compensate for residual sensor calibration biases and altitude computation errors originating from the underlying atmospheric model. Altitude is estimated over time using an extended Kalman filter, for which barometric noise errors have been carefully considered. The performance of the developed barometric vertical navigation system is evaluated with real test flight data collected at the German Aerospace Center (DLR) National Experimental Test Center for Unmanned Aircraft Systems. The results obtained for ground-corrected barometric geodetic altitudes suggest that the system can be used for redundant altitude determination during vertiport operations, especially in the case of GNSS interference. It also supports the harmonization of altitudes for a common altitude reference system.