React-G: GNSS Signal Multipath Simulation Framework for Small Uncrewed Aerial Systems

Bohan Zhang, Julian Gutierrez, and Ankit Agrawal

Peer Reviewed

Abstract:	Global Navigation Satellite System (GNSS) multipath errors pose significant challenges for small Uncrewed Aerial Systems (sUAS) operating in reflective environments, such as urban areas with glass facades. These reflections are one of several factors that complicate navigation. Conventional heuristic and machine learning methods may face limitations in generalizability or interpretability, particularly in complex urban settings, which can reduce their effectiveness in pre-flight planning, in-flight adaptation, and post-flight analysis. To address this, we propose Reflective Environment Augmented Coordinates Tracking of GNSS (React-G). This flexible simulation framework approximates multipath signal path behaviors and characterizes reflection-induced deviations across a range of GNSS simulation tasks. React-G integrates Unreal Engine, Google Maps 3D Tiles, and Cesium for Unreal to build digital models of real-world environments. Our approach uses a receiver-centric ray casting technique, inspired by Radio Frequency (RF) propagation principles, to simulate multipath reflection effects. The framework allows adjustments of parameters such as ray density, GNSS receiver placement, spatial boundaries, and material reflectivity to assess GNSS signal behavior across diverse scenarios. A comparative analysis with NASA’s NavQ system and real-world GNSS measurements shows React-G can approximate key aspects of GNSS signal paths, modeling both direct and indirect signal paths while accounting for surface reflections. The result suggests that, in areas with detailed 3D tile coverage, the widespread availability of Google Maps 3D Tiles may support the modeling of GNSS signal interactions across a range of urban environments. Beyond sUAS navigation resilience, React-G may also contribute to the evaluation of autonomous ground vehicle localization and offer insights for urban infrastructure design through GNSS signal interference analysis. Index Terms—GNSS, Multipath, Navigation, sUAS, Modeling, Simulation, NavQ, Urban Canyon, LOS, NLOS
Published in:	2025 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 28 - 1, 2025 Salt Lake Marriott Downtown at City Creek Salt Lake City, UT
Pages:	1170 - 1181
Cite this article:	Zhang, Bohan, Gutierrez, Julian, Agrawal, Ankit, "React-G: GNSS Signal Multipath Simulation Framework for Small Uncrewed Aerial Systems," 2025 IEEE/ION Position, Location and Navigation Symposium (PLANS), Salt Lake City, UT, April 2025, pp. 1170-1181.
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