A Ground-Based Augmentation System (GBAS) is a civil-aviation safety-critical system that supports local augmentation –at airport level– of the primary GNSS constellation(s). By providing enhanced levels of service it enables all phases of approach, landing, departure and surface operations notably under low visibility conditions.
One of the main sources of GBAS GNSS ranging error is the propagation delay induced by a particular layer of the earth’s atmosphere: the ionosphere. To overcome this integrity issue an ionospheric model was developed, based on ionospheric data collected over the last decade.
The detection of ionosphere spatial gradient is complex and challenging: a significant amount of GNSS raw data needs to be processed and the current processing techniques provide many “fake” gradients coming from measurement artefacts. As a result, a manual validation of the processing outcomes is required, which represent a significant amount of effort from skilled operators. As output of the current automatic processing, more than 90% of the detected gradients are classified as measurement artefact during the manual validation.