Seabed-to-Sky Mapping of Maritime Environments with a Dual Orthogonal SONAR and LiDAR Sensor Suite

TL;DR

This paper introduces a GNSS-independent seabed-to-sky mapping system for maritime environments, fusing LiDAR and dual orthogonal sonar sensors on an autonomous vehicle to produce real-time, unified 3D maps.

Contribution

It presents a novel integrated mapping system combining LiDAR-IMU and dual orthogonal sonars, extending fusion techniques and modifying LIO-SAM for continuous, real-time seabed-to-sky mapping.

Findings

Real-time operation at 2.65 Hz map updates

Successful mapping of air-water domains in real-world tests

Enhanced fusion of heterogeneous sensors for consistent 3D models

Abstract

Critical maritime infrastructure increasingly demands situational awareness both above and below the surface, yet existing ''seabed-to-sky'' mapping pipelines either rely on GNSS (vulnerable to shadowing/spoofing) or expensive bathymetric sonars. We present a unified, GNSS-independent mapping system that fuses LiDAR-IMU with a dual, orthogonally mounted Forward Looking Sonars (FLS) to generate consistent seabed-to-sky maps from an Autonomous Surface Vehicle. On the acoustic side, we extend orthogonal wide-aperture fusion to handle arbitrary inter-sonar translations (enabling heterogeneous, non-co-located models) and extract a leading edge from each FLS to form line-scans. On the mapping side, we modify LIO-SAM to ingest both stereo-derived 3D sonar points and leading-edge line-scans at and between keyframes via motion-interpolated poses, allowing sparse acoustic updates to contribute continuously to a single factor-graph map. We validate the system on real-world data from Belvederekanalen (Copenhagen), demonstrating real-time operation with approx. 2.65 Hz map updates and approx. 2.85 Hz odometry while producing a unified 3D model that spans air-water domains.