Underwater Dense Mapping with the First Compact 3D Sonar

TL;DR

This paper explores the use of the first compact 3D sonar for underwater dense mapping, introducing calibration, mapping, and SLAM techniques to improve underwater spatial understanding and localization.

Contribution

It presents the first comprehensive study on the performance and applications of a novel compact 3D sonar for underwater mapping and SLAM, including calibration procedures and environment assessments.

Findings

3D sonar enables detailed underwater reconstructions

Mapping pipelines work in challenging environments

Acoustic propagation remains a key challenge

Abstract

In the past decade, the adoption of compact 3D range sensors, such as LiDARs, has driven the developments of robust state-estimation pipelines, making them a standard sensor for aerial, ground, and space autonomy. Unfortunately, poor propagation of electromagnetic waves underwater, has limited the visibility-independent sensing options of underwater state-estimation to acoustic range sensors, which provide 2D information including, at-best, spatially ambiguous information. This paper, to the best of our knowledge, is the first study examining the performance, capacity, and opportunities arising from the recent introduction of the first compact 3D sonar. Towards that purpose, we introduce calibration procedures for extracting the extrinsics between the 3D sonar and a camera and we provide a study on acoustic response in different surfaces and materials. Moreover, we provide novel mapping and SLAM pipelines tested in deployments in underwater cave systems and other geometrically and acoustically challenging underwater environments. Our assessment showcases the unique capacity of 3D sonars to capture consistent spatial information allowing for detailed reconstructions and localization in datasets expanding to hundreds of meters. At the same time it highlights remaining challenges related to acoustic propagation, as found also in other acoustic sensors. Datasets collected for our evaluations would be released and shared with the community to enable further research advancements.