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Article

Indoor Pedestrian Location via Factor Graph Optimization Based on Sliding Windows

1
School of Instrument Science and Engineering, Southeast University, Nanjing 210096, China
2
School of Automation, Army Academy of Border and Coastal Defence, Kunming Campus, Kunming 650207, China
3
School of Automation, Nanjing University of Science and Technology, Nanjing 210094, China
4
Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
*
Author to whom correspondence should be addressed.
Sensors 2025, 25(17), 5545; https://doi.org/10.3390/s25175545
Submission received: 10 July 2025 / Revised: 9 August 2025 / Accepted: 1 September 2025 / Published: 5 September 2025
(This article belongs to the Section Navigation and Positioning)

Abstract

Global navigation satellite systems (GNSS) can provide high-quality location information in outdoor environments. In indoor environments, GNSS cannot achieve accurate and stable location information due to the obstruction and attenuation of buildings together with the influence of multipath effects. Due to the rapid development of micro-electro-mechanical system (MEMS) sensors, today’s smartphones are equipped with various low-cost and small-volume MEMS sensors. Therefore, it is of great significance to study indoor pedestrian positioning technology based on smartphones. In order to provide pedestrians with high-precision and reliable location information in indoor environments, we propose a pedestrian dead reckoning (PDR) method based on Transformer+TCN (temporal convolutional network). Firstly, we use IMU (inertial measurement unit)/PDR pre-integration to suppress the inertial navigation divergence. Secondly, we propose a step length estimation algorithm based on Transformer+TCN. The Transformer and TCN networks are superimposed to improve the ability to capture complex dependencies and improve the generalization and reliability of step length estimation. Finally, we propose factor graph optimization (FGO) models based on sliding windows (SW-FGO) to provide accurate posture, which use accelerometer (ACC)/gyroscope/magnetometer (MAG) data to establish factors. We designed a fusion positioning estimation test and a comparison test on step length estimation algorithm. The results show that the fusion method based on SW-FGO proposed by us improves the positioning accuracy by 29.68% compared with the traditional FGO algorithm, and the absolute position error of the step length estimation algorithm based on Transformer+TCN in pocket mode is mitigated by 42.15% compared with the LSTM algorithm. The step length estimation model error of Transformer+TCN is 1.61%, and the step length estimation accuracy is improved by 24.41%.
Keywords: GNSS; PDR; FGO; transformer; TCN GNSS; PDR; FGO; transformer; TCN

Share and Cite

MDPI and ACS Style

Cheng, Y.; Li, H.; Liu, X.; Chen, S.; Zhu, S. Indoor Pedestrian Location via Factor Graph Optimization Based on Sliding Windows. Sensors 2025, 25, 5545. https://doi.org/10.3390/s25175545

AMA Style

Cheng Y, Li H, Liu X, Chen S, Zhu S. Indoor Pedestrian Location via Factor Graph Optimization Based on Sliding Windows. Sensors. 2025; 25(17):5545. https://doi.org/10.3390/s25175545

Chicago/Turabian Style

Cheng, Yu, Haifeng Li, Xixiang Liu, Shuai Chen, and Shouzheng Zhu. 2025. "Indoor Pedestrian Location via Factor Graph Optimization Based on Sliding Windows" Sensors 25, no. 17: 5545. https://doi.org/10.3390/s25175545

APA Style

Cheng, Y., Li, H., Liu, X., Chen, S., & Zhu, S. (2025). Indoor Pedestrian Location via Factor Graph Optimization Based on Sliding Windows. Sensors, 25(17), 5545. https://doi.org/10.3390/s25175545

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