Underwater 3D positioning on smart devices

TL;DR

This paper introduces the first underwater acoustic positioning system for smart devices that enables relative localization without external infrastructure, using pairwise distances and orientation data to achieve median errors below 1.6 meters.

Contribution

It presents a novel distributed underwater localization system for smart devices that eliminates the need for external anchors or buoys.

Findings

Median localization errors of 0.5-0.9 meters

System scales linearly with number of devices

Effective in underwater deployments of 4-5 devices

Abstract

The emergence of water-proof mobile and wearable devices (e.g., Garmin Descent and Apple Watch Ultra) designed for underwater activities like professional scuba diving, opens up opportunities for underwater networking and localization capabilities on these devices. Here, we present the first underwater acoustic positioning system for smart devices. Unlike conventional systems that use floating buoys as anchors at known locations, we design a system where a dive leader can compute the relative positions of all other divers, without any external infrastructure. Our intuition is that in a well-connected network of devices, if we compute the pairwise distances, we can determine the shape of the network topology. By incorporating orientation information about a single diver who is in the visual range of the leader device, we can then estimate the positions of all the remaining divers, even if they are not within sight. We address various practical problems including detecting erroneous distance estimates, addressing rotational and flipping ambiguities as well as designing a distributed timestamp protocol that scales linearly with the number of devices. Our evaluations show that our distributed system running on underwater deployments of 4-5 commodity smart devices can perform pairwise ranging and localization with median errors of 0.5-0.9 m and 0.9-1.6 m