Geodetic Altitude From Barometer and Weather Data for GNSS Integrity Monitoring in Aviation

Abstract

Vertical navigation is crucial for safe aircraft separation and has been traditionally based on the pressure altitude provided by barometric altimeters. New aviation oper- ations require robust determination of geodetic altitude and are expected to primarily rely on global navigation satellite systems (GNSS). Since deviations between pressure and geodetic altitudes can reach hundreds of meters, an altitude harmonization is needed to use barometers in combination with GNSS. In this paper, we first present a methodology to compute accurate geodetic altitude from barometers and external weather data. Secondly, we derive error and threat models of this geodetic altitude. Finally, we employ these models within a GNSS integrity monitoring algorithm augmented with the derived altitude. We assess our methodologies against flight tests measurements and availability simulations of localizer performance with vertical guidance (LPV) operations. These analyses illustrate the potential benefits of employing barometers as augmentation or stand–alone systems for geodetic altitude navigation.