PT  - JOURNAL ARTICLE
AU  - Wen, Weisong
AU  - Pfeifer, Tim
AU  - Bai, Xiwei
AU  - Hsu, Li-Ta
TI  - Factor graph optimization for GNSS/INS integration: A comparison with the extended Kalman filter
AID  - 10.1002/navi.421
DP  - 2021 Jun 20
TA  - NAVIGATION: Journal of the Institute of Navigation
PG  - 315--331
VI  - 68
IP  - 2
4099  - https://navi.ion.org/content/68/2/315.short
4100  - https://navi.ion.org/content/68/2/315.full
SO  - NAVIGATION2021 Jun 20; 68
AB  - Factor graph optimization (FGO) recently has attracted attention as an alternative to the extended Kalman filter (EKF) for GNSS-INS integration. This study evaluates both loosely and tightly coupled integrations of GNSS code pseudorange and INS measurements for real-time positioning, using both conventional EKF and FGO with a dataset collected in an urban canyon in Hong Kong. The FGO strength is analyzed by degenerating the FGO-based estimator into an “EKF-like estimator.” In addition, the effects of window size on FGO performance are evaluated by considering both the GNSS pseudorange error models and environmental conditions. We conclude that the conventional FGO outperforms the EKF because of the following two factors: (1) FGO uses multiple iterations during the estimation to achieve a robust estimation; and (2) FGO better explores the time correlation between the measurements and states, based on a batch of historical data, when the measurements do not follow the Gaussian noise assumption.