3D Hybrid Localization Technology based on WiFi RTT and Pressure Sensor to Support Precise Vertical Takeoff and Landing of UAM

Jung Ho Lee, Chae Deok Lim, and Youngsu Cho

Abstract:	This paper proposes a 3D hybrid positioning technology that supports safe vertical takeoff and landing of UAMs using Wi-Fi and pressure sensors. To ensure safe movement within vertiports located in complex urban areas, UAMs require accurate position information. The IEEE 802.11mc protocol provides accurate distance information using fine time measurements (FTM) and can support various location-based services. The proposed technology utilizes Wi-Fi round-trip time (RTT) to provide accurate position information during UAM vertical movement. Calculating the 3D position of a UAM using Wi-Fi RTT requires at least three Access Points (APs) installed around the vertiport. Communication with each AP requires significant processing time. Because fast-moving UAMs travel significant distances during this processing time, this time can lead to significant positioning errors in conventional trilateration-based positioning technology. The proposed technology calculates the RTT to each AP based on altitude displacement information from a pressure sensor and uses this information, along with the measured RTT, to calculate the 3D position. In other words, the proposed technology minimizes positioning errors due to processing time by calculating a 3D position using a single RTT measurement and two or more calculated RTTs. To verify the performance of the proposed technology, four Wi-Fi APs were installed in an area with multiple buildings around the vertiport and vertical movement tests were conducted at an altitude range of up to 90 m above ground level (AGL). The proposed technology achieved a horizontal error of 0.39 m and a vertical error of 0.08 m at 1 sigma, achieving an overall positioning error of less than 1 m. This demonstrates that the proposed technology can be effectively utilized for the safe vertical takeoff and landing of UAMs in urban areas.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	1800 - 1805
Cite this article:	Lee, Jung Ho, Lim, Chae Deok, Cho, Youngsu, "3D Hybrid Localization Technology based on WiFi RTT and Pressure Sensor to Support Precise Vertical Takeoff and Landing of UAM," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 1800-1805. https://doi.org/10.33012/2025.20384
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