Inter-Pseudolite Range Augmented GNSS PPP Navigation for Airborne Pseudolite System

Ground-based pseudolite navigation systems have several limitations, such as low vertical accuracy, susceptibility to multipath effects, and near-far signal problems. These limitations could be addressed with an airborne pseudolite system. However, to ensure high user positioning accuracy the aerial signal transmitters have to be accurately positioned. Commonly used methods are based on the “inverted GNSS” principle, with ground stations monitoring the pseudolites, or the differential GNSS (DGNSS) technique with one or more reference stations. However, the inverted GNSS method introduces delay for user positioning, while DGNSS has stringent requirements that include simultaneous measurements made by both the pseudolite(s) and the reference station(s), and a limitation on the distance between pseudolite(s) and reference station(s). To address such problems the authors propose an airborne pseudolite system, consisting of some ground pseudolites (G-PLs) and airborne pseudolites (A-PLs). The A-PLs in the proposed system are positioned using the GNSS Precise Point Positioning (PPP) technique. To enhance the A-PL positioning performance, inter-PL range measurements could be used as additional observations. The performance of the proposed system is validated using simulation tests. The results show that A-PL achieves the best positioning accuracy with measurements from both G-PLs and limited GNSS satellites or only from GPLs where no satellite signals are available.