MetaBlue: A Metasurface-Assisted Acoustic Underwater Localization System

2026-02-22

AI Summary

This work proposes MetaBlue, a low-cost passive acoustic metasurface that, when paired with a standard ultrasonic transmitter, forms a directional “super-emitter” enabling high-accuracy angle-of-arrival estimation using only a single hydrophone. To eliminate the need for precise clock synchronization, the method leverages inherent low-frequency electromagnetic leakage from acoustic transducers as a timing reference, introducing a novel hybrid electromagnetic–acoustic time-of-arrival ranging technique. By embedding direction-dependent spectral signatures into the metasurface design, this approach achieves full 3D underwater localization with a single anchor node. Experimental results demonstrate an average angle-of-arrival error of 8.7° at ranges beyond 10 meters and positioning errors as low as 0.37 meters, maintaining sub-meter accuracy (≤0.73 m) even at the maximum tested range.

Technology Category

• Search and Optimization: Metareasoning and Metaheuristics
• Intelligent Robots: Localization, Mapping, and Navigation
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Search and Retrieval-Augmented AI: Multilingual and cross-lingual Web search
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Underwater localization is essential for marine exploration and autonomous underwater operations, yet existing radio frequency and optical approaches are limited by rapid attenuation or limited visibility. Acoustic sensing remains the most practical choice, but conventional acoustic systems typically rely on large arrays or multiple synchronized anchors, resulting in high hardware costs and complex deployment. This paper introduces a novel low-cost passive acoustic metasurface, MetaBlue , explicitly designed for underwater localization, which, when attached to an ordinary ultrasonic transmitter, transforms it into a directional "super-transmitter." The metasurface embeds direction-dependent spectral patterns into the transmitted waveform, enabling accurate angle-of-arrival (AoA) estimation using only a single hydrophone. For ranging, we present a new EM-acoustic mixed time-of-arrival (ToA) method that leverages the acoustic transducer's inherent low-frequency EM leakage as a timing reference, enabling precise ranging without shared clocks. This allows complete 3D localization with a single low-cost anchor. We evaluate the system across diverse real-world underwater settings, including pools, tanks, and outdoor environments. Experiments show that our design achieves an average AoA error of 8.7 degree and 3D localization error of 0.37 m at distances over 10 m. Even with a single anchor, the system maintains 0.73 m precision.

Problem

• underwater localization
• acoustic sensing
• angle-of-arrival
• time-of-arrival
• metasurface

Innovation

• metasurface
• underwater localization
• angle-of-arrival (AoA)
• time-of-arrival (ToA)
• single-anchor