Evaluation of Dual Frequency GBAS Performance using Flight Data

Abstract

In this paper, we describe the results of dual frequency Ground Based Augmentation System (GBAS) performance using data from DLR’s experimental GBAS testbed and flight trials carried out at the research airport in Braunschweig, Germany. We show the results of noise and multipath evaluation of the new L5 signals from the GPS Block IIF satellites and their application in our experimental GBAS ground station. Results show that, due to the long smoothing time in GBAS processing, there is no clearly visible improvement in terms of , despite the fact that noise and multipath is significantly lower on the raw (unsmoothed) L5 signals compared to the currently used L1 signals. Two proposed dual-frequency smoothing techniques (Divergence Free and Ionosphere Free) are implemented in the ground and airborne subsystems and tested in comparison with single frequency GBAS performance. During the flight trials, no ionosphere anomaly was observed, thus nominal behavior is presented. In offline analysis, we injected a simulated ionospheric gradient into these raw measurements to compare and evaluate the dual frequency and single frequency techniques and the output of the relevant monitors.