Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry

Xu, Ziyin; Wang, Xianyi; Xia, Junming; Sun, Yueqiang; Liu, Cheng; Wang, Zhuoyan; Tian, Yusen; Qiu, Tongsheng; Wang, Dongwei

doi:10.3390/rs18060893

Open AccessArticle

Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry

by

Ziyin Xu

^1,2,3

,

Xianyi Wang

^1,2,3,*

,

Junming Xia

^1,2,3

,

Yueqiang Sun

^1,2,3,

Cheng Liu

^1,2,3,

Zhuoyan Wang

^1,2,3,

Yusen Tian

^1,2,3,

Tongsheng Qiu

^1,2,3

and

Dongwei Wang

^1,2,3

¹

National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China

²

University of Chinese Academy of Sciences, Beijing 100049, China

³

Beijing Key Laboratory of Space Environment Exploration, Chinese Academy of Sciences, Beijing 100190, China

^*

Author to whom correspondence should be addressed.

Remote Sens. 2026, 18(6), 893; https://doi.org/10.3390/rs18060893

Submission received: 12 February 2026 / Revised: 5 March 2026 / Accepted: 12 March 2026 / Published: 14 March 2026

(This article belongs to the Special Issue Advancing UAV-Based Remote Sensing: Innovations, Techniques and Applications (Second Edition))

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Abstract

GNSS reflectometry (GNSS-R) altimetry has been widely used for retrieving surface elevation over oceans, cryosphere, and land. Recently, UAV-borne GNSS-R systems have gained attention due to their flexibility for low-altitude and localized observations. However, lightweight UAV platforms impose strict payload and real-time processing constraints. At low altitudes, the small geometric delay between direct and reflected signals often leads to waveform overlap, degrading conventional altimetry algorithms. In this study, a lightweight UAV-borne GNSS-R receiver and a signal-separation-based altimetry method are proposed. Direct and reflected signals are separated using waveform characteristics without relying on external height information, mitigating the impact of waveform overlap. Simulations and experiments using a SPIRENT 9000 GNSS simulator demonstrate stable height retrieval under dynamic low-altitude conditions while maintaining real-time capability, confirming the feasibility of lightweight UAV GNSS-R altimetry for rapid elevation monitoring.

Keywords: GNSS-R; UAV altimetry; signal separation algorithm; waveform overlap mitigation

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MDPI and ACS Style

Xu, Z.; Wang, X.; Xia, J.; Sun, Y.; Liu, C.; Wang, Z.; Tian, Y.; Qiu, T.; Wang, D. Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry. Remote Sens. 2026, 18, 893. https://doi.org/10.3390/rs18060893

AMA Style

Xu Z, Wang X, Xia J, Sun Y, Liu C, Wang Z, Tian Y, Qiu T, Wang D. Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry. Remote Sensing. 2026; 18(6):893. https://doi.org/10.3390/rs18060893

Chicago/Turabian Style

Xu, Ziyin, Xianyi Wang, Junming Xia, Yueqiang Sun, Cheng Liu, Zhuoyan Wang, Yusen Tian, Tongsheng Qiu, and Dongwei Wang. 2026. "Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry" Remote Sensing 18, no. 6: 893. https://doi.org/10.3390/rs18060893

APA Style

Xu, Z., Wang, X., Xia, J., Sun, Y., Liu, C., Wang, Z., Tian, Y., Qiu, T., & Wang, D. (2026). Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry. Remote Sensing, 18(6), 893. https://doi.org/10.3390/rs18060893

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Separation of Overlapped Direct and Reflected Waveforms for Low-Altitude UAV-Based GNSS-R Altimetry

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