Optimization-Based Estimation and Factor Graphs

factor graph optimizationFGOGNSS/INSRTKPPP-RTKsmoothingnonlinear optimizationrobust estimationsensor fusion

Factor graph optimization is the mathematical engine that links signals, measurements, maps, sensors, and integrity. We use it as a unifying framework for GNSS, INS, carrier phase, Doppler, maps, constraints, perception, and integrity reasoning — letting navigation systems reason over time, fuse heterogeneous measurements, and handle outliers more flexibly than classical filtering-only pipelines.

The foundational paper Factor Graph Optimization for GNSS/INS Integration: A Comparison with the Extended Kalman Filter (Wen, Pfeifer, Bai, Hsu, NAVIGATION 2021) was named the 2024 Most-Cited Paper in NAVIGATION: Journal of the Institute of Navigation. The follow-on work extends FGO into integrity-constrained estimation, smartphone IMU-only indoor SLAM (IEEE TAES 2024), 3D vision-aided GNSS RTK (NAVIGATION 2023), and self-supervised weighting (AutoW, ION GNSS+ 2024). The open-source GraphGNSSLib library is the community-facing artifact of this pillar.

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