Non-Gaussian Error Modeling for GBAS Integrity Assessment

Abstract

Four basic error sources exist for residual pseudorange error in a single frequency differential GPS system for ground based augmentation (GBAS): signal multipath, increased receiver noise C/N0 due to interference, residual differential troposphere error due to the applied troposphere model and the error induced by ionosphere gradients. Without using classical Gaussian overbounding, we combine their probability density functions to a joint pseudorange error distribution. This distribution is propagated through the GBAS Hatch filter and then mapped into the position domain using a worst case constellation observed at Braunschweig Airport, Germany. Our calculations using the unapproximated PDFs yield a significant reduction amounting to over 50% of the position domain error at the 2x10^7 integrity risk level when compared to the classical Gaussian overvounding approach.