Enhanced LEO-based Doppler Positioning: A Digital Terrain Model Registration Approach for Accurate 3D Navigation

Qamar Bader, Aboelmagd Noureldin

Peer Reviewed

Abstract:	The advent of Low Earth Orbit (LEO) satellite constellations has spurred the development of novel positioning approaches that complement traditional GNSS, particularly through the use of Doppler-based measurements. However, Doppler-only systems suffer from poor vertical observability, resulting in significant altitude errors that undermine overall 3D positioning accuracy. To overcome these limitations, this paper presents a Digital Terrain Model (DTM)-aided Doppler positioning framework that integrates high-resolution LiDAR-derived DTMs with a Cubature Kalman Filter (CKF) for enhanced state estimation. An efficient online KD-tree search algorithm is employed to rapidly extract relevant altitude information from massive DTM datasets, ensuring that the external altitude updates are available in real-time. Experimental results reveal that the incorporation of DTM-derived altitude updates dramatically reduces errors along the vertical channel; for instance, lowering the altitude RMS error from approximately 10.34 m to 0.4585 m—while concurrently improving velocity estimates. Validation on a 5 km suburban trajectory in Kingston, Ontario, using a high-end reference system demonstrates that our method reduces the overall 3D RMS error by more than 50% and enhances the horizontal position performance, thus offering a robust solution for 3D navigation in environments where conventional GNSS performance is compromised.
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:	2659 - 2670
Cite this article:	Bader, Qamar, Noureldin, Aboelmagd, "Enhanced LEO-based Doppler Positioning: A Digital Terrain Model Registration Approach for Accurate 3D Navigation," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 2659-2670. https://doi.org/10.33012/2025.20432
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