On-Board GPS Augmentation through RADAR Altimeter Aiding for Precision Approach and Landing of UAS

RADAR Altimeter Aiding (RALT Aiding) is an augmentation method to GPS to improve the standard GPS position solution accuracy, integrity, and continuity through the inclusion of an additional range measurement into the GPS measurement equation. This additional range measurement is derived through the combination of a radar altimeter and terrain elevation database. This paper extends on work previously competed by the authors and provides an in-depth introduction to the RALT Aiding method, description of work completed in the past, and outlook for the future of the concept.