In Global Navigation Satellite System (GNSS)-degraded environments, pseudolites (PLs) provide additional signal sources to enhance positioning performance, but their integration in optimization-based frameworks remains limited. This paper presents a loosely coupled factor graph optimization (FGO) framework that fuses the GNSS/PL least-squares (LS) solutions with inertial measurement unit (IMU) data. The evaluation considers low GNSS visibility scenarios with four high-elevation GNSS satellites and up to two PL transmitters over an 80~s window. FGO achieves a 22.8\% to 41.3\% reduction in mean 3D error compared to standard LS methods. Compared to a GNSS-IMU baseline, incorporating PL transmitters further improves positioning accuracy, with performance depending on geometry.
@article{arxiv.2605.24980,
title = {Loosely Coupled Factor Graph Optimization for Pseudolite-Augmented Navigation},
author = {Chih-Chun Chen and Lipeng Tan and Shiyu Bai and Heike Vallery},
journal= {arXiv preprint arXiv:2605.24980},
year = {2026}
}