Multi-Modal Sonar Mapping of Offshore Cable Lines with an Autonomous Surface Vehicle

Abstract

Monitoring offshore infrastructure is a challenging task owing to the harsh ocean environment. To reduce human involvement in this task, this study proposes an autonomous surface vehicle (ASV)-based structural monitoring system for inspecting power cable lines under the ocean surface. The proposed ASV was equipped with multimodal sonar sensors, including a multibeam echosounder (MBES) and side-scan sonar (SSS) for mapping the seafloor, combined with a precisely estimated vehicle pose from navigation sensors. In particular, a globally consistent map was developed using the orthometric height as a vertical datum estimated based on the geoid height received from the GPS. Accordingly, the MBES and SSS generate a map of the target objects in the form of point clouds and sonar images, respectively. Dedicated outlier removal methods for MBES sensing were proposed to preserve the sparse inlier point cloud, and we applied the projection of the SSS image pixels to reflect the geometry of the seafloor. A field test was conducted in an ocean environment using real offshore cable lines to verify the efficiency of the proposed monitoring system.

Exploring Autonomous and Remotely Operated Vehicles in Offshore Structure Inspections

“…They are equipped with advanced instrumentation and measurement systems to perform subaquatic tasks and gather data for analysis, as shown by [18,19]. AUVs have also been used to map the seafloor and inspect cable and pipelines under the ocean surface, utilising multimodal sonar sensors for accurate mapping and monitoring [20]. AUVs have recently undergone significant advancements in terms of operational range and endurance due to the new battery technology, and certain AUV models are now capable of several days of autonomous operation, as recently demonstrated by the HUGIN© endurance AUV.…”

“…By minimising human error and reducing risks associated with manned operations, ASVs greatly improve the efficiency of maintenance schedules and potential threat assessments. These vehicles are designed to operate in harsh ocean environments and reduce human participation in offshore infrastructure monitoring [20].…”

Synthetic Maritime Traffic Generation System for Performance Verification of Maritime Autonomous Surface Ships

“…The key technologies used in MASS include sensing the surrounding environment using various sensors (e.g., radar, sonar, light detection and ranging, GPS, and cameras) [11][12][13][14][15], artificial intelligence (AI) and machine learning technologies that are used to direct the navigation by analyzing the sensor data [16,17], and navigation automation systems that set the course of a ship, adjust its speed, and automatically perform navigation tasks (e.g., collision avoidance) [18][19][20][21]. One crucial challenge involves the development of robust path planning and collision avoidance systems capable of navigating waters safely, considering the presence of other autonomous and traditional vessels, and adhering to the rules of the road at sea as defined by the Convention on the International Regulations for Preventing Collisions at Sea (COLREG).…”

Attitude-Independent Route Tracking for Subsea Power Cables Using a Scalar Magnetometer under High Sea Conditions

“…Sonar is the main equipment used for acoustic detection. High-resolution sonar instruments, such as multibeam sonar [10], synthetic aperture sonar [11], and side-scan sonar [12], are needed for subsea cable-like object detection. In order to widen the frequency band, biosonar is used for cable detection [13].…”