Determination of GPS positioning errors due to multi-path in civil aviation

Fully automated landing systems based on GPS still suffer from errors, mainly due to multipath propagation. This paper presents a simulation tool to quantify positioning errors by combining a ray-tracing based three-dimensional multipath propagation model with a standard GPS receiver model. The propagation model accounts for the reflecting environment geometry, transmitting and receiving antenna patterns, reflections and depolarization. For each ray the time delay, carrier phase delay and multipath-to-direct amplitude ratio is computed and fed into the receiver model to determine the pseudorange errors. The performance of the method is illustrated with numerical examples.