Factor graph optimization for GNSS/INS integration: A comparison with the extended Kalman filter

Weisong Wen, Tim Pfeifer, Xiwei Bai, Li Ta Hsu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

93 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)315-331
Number of pages17
JournalNavigation, Journal of the Institute of Navigation
Issue number2
Publication statusPublished - 1 Jun 2021


  • extended Kalman filter
  • factor graph optimization
  • GNSS
  • INS
  • integration
  • navigation
  • positioning
  • urban canyons
  • window size

ASJC Scopus subject areas

  • Aerospace Engineering
  • Electrical and Electronic Engineering


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