The Effect of Coarse Doppler Resolution on the Performance of a Vertical Synthetic Aperture Radar Navigation System

Tucker Haydon, Todd E. Humphreys

Abstract:	The trusted inertial terrain-aided navigation (TITAN) algorithm correlates vertical synthetic aperture radar (VSAR) range-Doppler measurements against a digital terrain elevation model to determine the position and velocity of an airborne radar without input from global navigation satellite systems (GNSS). Recent work has characterized the navigation performance of the TITAN algorithm when the radar Doppler resolution is assumed to be infinitely fine. Hyperfine Doppler resolution, however, comes at a cost: synthetic aperture processing requires the length and number of radar pulses in an aperture to increase with finer Doppler resolutions. Consequently, the size of VSAR images, the computational resources required to process these enlarged images, and the total energy required by the greater number of radar pulses all increase. Therefore, for remote navigation systems with limited computational processing and energy budgets, it is desirable to keep the Doppler resolution of a navigation VSAR coarse, provided that this coarsening does not significantly degrade navigation performance. Existing work has not characterized how the performance of the TITAN algorithm varies with Doppler resolution, so it is difficult to determine an appropriate Doppler resolution given navigation accuracy requirements. This paper addresses this gap and analyzes how TITAN’s signal-to-noise ratio, ranging errors, and navigation accuracy are affected by Doppler resolution. The study concludes that there is little correlation between overall navigation performance and Doppler resolution when the number of navigation observables is fixed.
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:	1585 - 1601
Cite this article:	Haydon, Tucker, Humphreys, Todd E., "The Effect of Coarse Doppler Resolution on the Performance of a Vertical Synthetic Aperture Radar Navigation System," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 1585-1601. https://doi.org/10.33012/2025.20275
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