Underwater Acoustic Ranging Between Smartphones

TL;DR

This paper introduces a new underwater acoustic ranging system for smartphones that achieves accurate distance measurements using existing hardware, overcoming multipath effects and clock drifts, enabling widespread underwater localization.

Contribution

The work presents the first real-time underwater ranging protocol for commodity smartphones that handles multipath and clock drift without extra hardware.

Findings

Median errors of 0.48-0.86 m at 35 m distance

Operates across different smartphone models

Works reliably despite clock drifts

Abstract

We present a novel underwater system that can perform acoustic ranging between commodity smartphones. To achieve this, we design a real-time underwater ranging protocol that computes the time-of-flight between smartphones. To address the severe underwater multipath, we present a dual-microphone optimization algorithm that can more reliably identify the direct path. Our underwater evaluations show that our system has median errors of 0.48-0.86 m at distances upto 35 m. Further, our system can operate across smartphone model pairs and works in the presence of clock drifts. While existing underwater localization research is targeted for custom hydrophone hardware, we believe that our work breaks new ground by demonstrating a path to bringing underwater ranging capabilities to billions of existing smartphones, without additional hardware.