Magnetic flux density (MFD) fingerprint map matching is a technique which can provide absolute position solutions by comparing a series of MFD measurements with a database [1–4]. The standard technique of fingerprint map matching relies on consistent measurement of the same physical phenomena during the survey (mapping) and the location phases [4]. However, fluctuations in MFD due to AC electricity, influenced by dynamic power requirements like the operation of a 3 KW kettle, challenge standard fingerprint map matching (Figure 1).

This paper addresses this challenge by employing spectral filtering to isolate MFD from AC sources in both the database creation and navigation phases. The resulting isolation of this temporal variable source enhances the base map's resilience to changes over time, ensuring its functionality regardless of the building's power status. This is particularly vital for applications such as firefighting operations, where the base map's effectiveness is crucial irrespective of the presence or absence of AC mains current.

The experimental environment for this paper is outdoors, which enables full control of the magnetic environment, in which a simulation of unshielded underfloor cables is used (Figure 2). The experiment involves a single AC source alongside multiple DC sources (Figure 3). This filtering technique should work anywhere and future work could bring this technique indoors. By using a variety of different magnetometers with different sampling rates the effectiveness of the filtering is analysed.

In conclusion, this study enhances MFD fingerprint map matching by effectively isolating AC-induced variability, setting the stage for increased robustness of this technique for future applications in indoor navigation.

References

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3. Ashraf I, Zikria Y Bin, Hur S, Park Y. A Comprehensive Analysis of Magnetic Field Based Indoor Positioning with Smartphones: Opportunities, Challenges and Practical Limitations. IEEE Access [Internet]. 2020 [cited 2022 Sep 13];8:228548–71. Available from: https://ieeexplore.ieee.org/document/9301308/
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