Autonomous bathymetric survey in the UK Atlantic

Ensuring safe and efficient maritime navigation is a critical task for coastal nations, but can also be a lengthy and costly exercise. The UK Hydrographic Office (UKHO) is responsible for charting millions of square kilometres of seabed, including some of the busiest shipping lanes in the world. To help advance this objective, the UKHO chose XOCEAN to provide accurate, high-quality and reliable hydrographic survey data using uncrewed surface vessels (USVs). Notably, XOCEAN was contracted in late 2023 to carry out a comprehensive bathymetric survey under the UK SW Approaches Lot 1 of the Seabed Mapping Framework.

Five XOCEAN USVs, outfitted with sophisticated multibeam echosounder (MBES) technology, were used over two areas, covering a combined 2,218km², south-west of the Isles of Scilly. The survey was methodically organized, from planning to mobilization out of St Marys on the Isles of Scilly. Operations ran across two phases, an initial acquisition phase and then infill and detailed wreck investigation surveys. Operated remotely via satellite, the use of USVs enhanced both safety and efficiency. XOCEAN’s highly flexible operational structure meant it could easily navigate the harsh environmental conditions posed by a winter season (November–March) deployment and the logistical complexities of deploying uncrewed vessels from a small island off the UK mainland, minimizing costs and schedule risk.

Introduction and background

For more than 225 years, the UKHO has been mapping and updating charts that enable it to provide reliable navigation data for safe and efficient maritime navigation. It is a huge task, with a vast territory to cover and continuous updates. Updating areas with low-resolution and outdated information is a priority, as is using viable alternatives to traditional survey approaches that can make operations more efficient and achieve carbon reduction targets. This is why UKHO was keen to prove the use of uncrewed technology for large-scale civil hydrography data collection and chose XOCEAN as its data provider.

Since it was founded in 2017, XOCEAN has been dedicated to harnessing the potential of USVs to deliver accurate and reliable hydrographic survey data. Its vision is to transform traditional survey methods by using innovative technology and uncrewed systems. Through honing its expertise and cultivating partnerships, the company has become a leading player in civil hydrography, delivering the superior hydrographic data needed for effective maritime navigation and environmental management.

The project involved a comprehensive bathymetric survey of the Haddock Bank area, 30–60 nautical miles south-west of the Isles of Scilly, off the UK coast, and covered two distinct areas with a combined area of 2,218km² in 100–120m water depths.

Five USVs, equipped with MBES technology, were piloted remotely from shore to collect high-resolution seabed and backscatter data to International Hydrographic Organization (IHO) Order 1a standards.

This pioneering approach both enhanced the safety of survey operations, by allowing pilots and surveyors to remain onshore, and ensured continuous, real-time monitoring and data collection through the use of enhanced satellite communications.

Challenges and objectives

XOCEAN’s project for the UKHO involved overcoming a series of significant challenges, all tied to stringent objectives aimed at advancing hydrographic survey capabilities. The primary scope was comprehensive multibeam bathymetric data acquisition, including backscatter, high-resolution data over 53 charted wrecks. The project was scoped to complete more than 10,000 line kilometres of survey using five USVs over 100 acquisition days.

The first challenge concerned environmental and operational conditions. The survey area, in the Southwest Approaches to the UK, is exposed to the harsh winter Atlantic swell, experiencing significant wave heights (Hs) of more than 2m, routinely reaching up to 3.5m. These conditions required the careful management of risks and operational difficulties. A second challenge was logistical coordination. The mobilization and demobilization of multiple USVs required careful planning. This was further complicated by the operations being based out of a small harbour on a remote island, which demanded efficient planning of spares and effective supply chain and contracting strategies to support the remote operations. XOCEAN’s flexible operational structure navigated these challenges. It could take advantage of the ability to launch and recover the USVs across a wide variety of slipways and crane facilities and to redeploy project teams during weather downtime to avoid unnecessary costs.

Another challenge was the technical and quality standards. Meeting the IHO Order 1a standards as specified in the “Standards for Hydrographic Surveys, Special Publication No. 44, 6th Edition, 2020”, along with the UKHO’s stringent technical requirements, was crucial. This included additional survey system verifications such as MBES repeatability tests, infill and detailed wreck surveys.

One of the survey objectives was to maximize resource efficiency. Using a remote operations model, XOCEAN aimed to maximize the use of its resources during favourable weather conditions while reallocating crew to other surveys during periods of downtime. This approach optimized operational efficiency and ensured continuous data acquisition, which was critical for meeting the project timelines. Another objective was to ensure high-quality data collection. The goal was to provide full coverage MBES and conduct crosslines every 5km or a minimum of five per survey block to meet the high standards required for hydrographic data accuracy and repeatability. The third objective concerned adaptability and safety. The use of USVs was strategically chosen to mitigate the risks associated with operating in challenging sea conditions, thereby enhancing the safety of survey operations and reducing seafarer exposure hours.

Solutions

XOCEAN adopted a multifaceted approach to address the challenges presented by the UKHO hydrographic survey project. First, it made use of advanced sonar technology and selection. To ensure high-resolution seabed mapping, XOCEAN equipped the XO-450 USVs with state-of-the-art NORBIT WINGHEAD B51s 200kHz sonars. These sonars were chosen for their wide swath capabilities and high data quality, making them ideal for the precise and detailed bathymetric survey data required. The selection of the NORBIT WINGHEAD sensors was strategic, focusing on their compatibility with the USVs and their reported performance in deepwater surveys. The sensors were configured to optimize data acquisition in the challenging conditions of the survey area, with specific settings tailored to handle the wide range of depths and sea states encountered during the project

Secondly, innovative software was used for data processing. XOCEAN used the latest CARIS software for hydrographic data processing, facilitating the efficient handling of large datasets and enabling real-time processing and visualization of multibeam echosounder data. The use of CARIS also helped in maintaining consistency across the data management process, ensuring that all collected data adhered to the UKHO’s stringent quality standards. A robust data management strategy was also crucial for the success of the survey. This strategy included rigorous data consistency checks and validation protocols to ensure that all collected data met the high-quality standards required for marine navigation and safety.

Thirdly, the integration of Starlink ensured enhanced communication and data transfer. XOCEAN has integrated Starlink satellite communication technology onboard its fleet of USVs. This provided high-speed, low-latency internet connectivity, enabling seamless data transfer and real-time communication between the remote operators and the vessels. The use of Starlink allowed for immediate data processing and analysis, significantly accelerating the decision-making process and ensuring timely delivery of survey results.

Finally, detailed hindcast weather modelling was used to understand the expected operable uptime for acquisition, helping to inform and optimize the number of USVs required to meet the project deadlines.

Implementation

The SW Approaches Lot 1 implementation was carefully orchestrated across several phases, each critical to project success. The first phase was commissioning at XOCEAN Ireland. This included calibrating the NORBIT WINGHEAD B51s 200kHz sonars and integrating Starlink communication systems onto the USVs.

Following commissioning, the project moved to mobilization out of St Marys on the Isles of Scilly. During mobilization, the team deployed the USVs and ensured all systems were fully operational and optimized for the initial survey operations. The first survey phase, Phase 1, took place in the Haddock Bank area of the Southwest Approaches. This phase involved comprehensive seabed mapping to capture initial bathymetric and backscatter data, with continuous real-time data transmission via Starlink for immediate processing and analysis. The transition between Phase 1 and Phase 2 involved reconfiguration and resupply of the USVs at St Marys, preparing for a focused survey of infill areas and detailed wreck surveys. Phase 2 was followed by a demobilization period where the USVs were retrieved and equipment was checked.

In addition to the main survey phases, the project schedule included periods for weather standby at St Marys to ensure safety and operational readiness in response to changing weather conditions, maximizing survey efficiency during suitable periods.

The data processing and delivery of raw deliverables were handled by XOCEAN. This included processing all collected data to meet the project’s quality standards and preparing initial reports. The final analysis and detailed reporting will follow on from the main processing phase and raw data delivery.

Throughout the project, rigorous mission planning, robust hindcast weather modelling and analysis of weather statistics were critical. A strategic approach both optimized the deployment of resources and ensured high standards of data accuracy and project deliverables, showcasing XOCEAN’s capability to manage complex maritime projects.

Results

XOCEAN’s deployment of five USVs off the Isles of Scilly marked a significant achievement in civil hydrographic surveying for the UKHO. The USVs, operated by pilots and surveyors from onshore locations, conducted extensive bathymetric surveys of the seabed, enhancing the understanding of underwater features ranging from depth variations and habitats to ridges, boulders and shipwrecks.

The data collected from these surveys both met and surpassed rigorous IHO Order 1a standards, achieving an unprecedented level of precision. This high-quality data will be crucial in the production of accurate nautical charts, significantly enhancing maritime navigation safety. Additionally, the data will support extensive marine environmental assessments and advanced sustainable practices within the blue economy.