HYDRO 2-2025 by Geomares Publishing

Canada’s pioneering role in hydrography

Hydrographer General of Canada Manon Larocque on S-100 sea trials, digital innovation and the challenges of the country’s vast and complex marine environment

Airborne Lidar and photogrammetric accuracy

Mapping the largest known cold-water coral reef habitat

Robotic intelligence for subsea cable inspection

Director Strategy & Business Development

Durk Haarsma

Financial Director Meine van der Bijl

Editorial Board Huibert-Jan Lekkerkerk, Mark Pronk, BSc, Marck Smit, Auke van der Werf

Head of Content Wim van Wegen

Copy Editor Serena Lyon

Marketing Advisors Myrthe van der Schuit, Peter Tapken, Sandro Steunebrink

Circulation Manager Adrian Holland

Design Persmanager, The Hague

Hydro International is an independent international magazine published by Geomares. The magazine and related e-newsletter inform worldwide professional, industrial and governmental readers of the latest news and developments in the hydrographic, surveying, marine cartographic and geomatics world. Hydro International encompasses all aspects, activities and equipment related to the acquisition, processing, presentation, control and management of hydrographic and surveyingrelated activities.

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Better together

On the day I chose to write this editorial, I read on the International Hydrographic Organization (IHO) website that it “proudly welcomes the Republic of The Gambia as its newest Member State.” If I have counted correctly, the West African country is now Member State 101, succeeding the significant milestone of the 100th country to become a member – an honour that fell to Kiribati – and so the counter keeps running. I am very curious to see which countries will follow in the coming years!

Let us first focus more specifically on The Gambia: despite the crucial role of maritime transport for the country’s economy, it faces significant hydrographic challenges. Many rivers and coastal areas have not been mapped or surveyed since at least the 1940s. This limits the safety of navigation, port efficiency and the ability to effectively manage the marine environment. Joining the IHO places The Gambia in the best company when it comes to the deepest knowledge of the hydrographic field, and the environment will certainly help the country forward. This is acknowledged by the country’s responsible minister. Speaking about the important milestone, the Minister of Transport, Works and Infrastructure of The Gambia, Ebrima Sillah, emphasized that joining the IHO marks a strategic advancement for the country. He noted that the move reflects The Gambia’s dedication to global maritime standards and its ambition to enhance navigational safety, boost economic development and safeguard marine resources. “By aligning with international best practices in hydrography,” he stated, “The Gambia positions itself as a responsible maritime player, ensuring safer waters for our shipping industry and sustainable practices for future generations.”

Collaboration takes us all further – a lesson many of us first learned in primary school. Sadly, the tensions and conflicts in today’s world show that this early insight, and the core value of working together, can no longer be taken for granted. The ability to achieve things collectively seems less obvious than it once was – a real pity, and a source of countless missed opportunities. That is why I find myself especially heartened by good news about successful collaborations. The continued growth of the international hydrographic community is one such example – and it genuinely brings me joy.

As an IHO Member State, The Gambia now stands to benefit from increased international cooperation, technical support and access to global best practices in several key areas, which will open the door to new opportunities. The Gambia will now have access to a wide range of capacity-building initiatives and a global network of experts. With these resources, The Gambia can strengthen its capabilities in conducting multibeam surveys and interpreting seabed geology; key steps towards unlocking future opportunities for resource development.

Celebrated on 21 June, World Hydrography Day raises awareness of the vital role that hydrography plays in deepening our understanding of the world’s seas and oceans. This year’s theme, Seabed Mapping: Enabling Ocean Action, highlights a goal that can only be achieved through shared commitment and cooperation.

With 101 Member States, the IHO is moving steadily in the right direction – a growing testament to what can be accomplished when nations come together. The years ahead will reveal which countries will step forward as members 102, 103, 104, 105 and beyond. Because in hydrography, as in so many things, we are simply better together.

Wim van Wegen

Head of content, Hydro International wim.van.wegen@geomares.nl

Picotech Ltd Launch Podlet for BlueBoat

Picotech Ltd recently released Podlet - a turnkey survey package for IHO Special Order Multibeam Surveys onboard BlueRobotics’ BlueBoatTM

BlueBoat+Podlet fits fully rigged in the trunk of a small hatchback and can be handlaunched and recovered at point of survey by one person. With the lowest power consumption, it delivers the longest endurance for seamless, high-precision hydrographic data collection—all in a one-person portable package (combined mass just 21kg).

Peerless at its price point, Podlet is supported by industry standard acquisition and processing software, BeamworX®, EIVA NaviSuite®, Xylem HYPACK®, Teledyne PDS® and QPS QINSy® and offers bathymetry and backscatter (snippets) as standard.

New digital platform from Kongsberg Discovery targets ocean data efficiency

Kongsberg Discovery has unveiled Geomatics, a new digital toolset aimed at simplifying the way marine professionals collect, handle and access ocean data. Developed by the company’s underwater robotics and sensor specialists, the platform is designed to bring greater efficiency and clarity to complex data environments. Launched at Ocean Business 2025, the solution enables both traditional and uncrewed vessel operators to streamline data operations, unlock operational insights and improve global collaboration between vessels and shore-based teams. Geomatics is the latest addition to Kongsberg Discovery’s Blue Insight ecosystem, delivering smarter data workflows and real-time visibility across diverse ocean sensor networks. Geomatics operates as the first Blue Insight product, collecting a suite of software services on the platform to simplify ocean data management. There are a compelling range of headline benefits. These include centralized data collection and logging from all onboard and remote sensors, automatic cataloguing and indexing to prepare data for exploration and analysis, and seamless data distribution to mirrored cloud environments or other data management systems. The Geomatics architecture is AI and machine learning ready, building a foundation for the integration of digital twin technology and further enhancing processing capabilities. A new Analytics product is also under development, allowing for automated processing and in-depth data analysis.

The Geomatics interface displays survey lines alongside metadata and related assets. The toolkit is designed to enhance underwater data operations. (Image courtesy: Kongsberg Discovery)

Learn more

An impression of the new EMODnet Bathymetry DTM, showcasing the Channel Islands, an archipelago in the English Channel off the coast of Normandy, France. (Image courtesy: EMODnet Bathymetry)

EMODnet Bathymetry 2024 DTM strengthens marine mapping with updated data

The latest release of the EMODnet Bathymetry digital terrain model (DTM) marks a significant step in advancing marine mapping. Developed with the support of the European Commission and the EMODnet Bathymetry consortium, the 2024 update benefits from contributions from a broad network of experts. This iteration features an improved resolution of 1/16 × 1/16 arc minutes (approximately 115 × 115 metres), covering European seas and selected global regions. It integrates data from acoustic surveys, airborne bathymetric Lidar and satellite-derived bathymetry from platforms such as Sentinel-2. The reference layer and quality index now link to 22,063 dataset entries, including 21,890 bathymetric surveys and 173 composite DTMs, which is an increase of 126 datasets since 2022. The dataset catalogue has expanded to 43,092 unique survey descriptions and 299 composite DTM or satellite-derived products, extending coverage beyond European coasts in collaboration with the European SeaDataNet infrastructure.

Teledyne Valeport launches self-calibrating pH sensor

Teledyne Valeport, in strategic collaboration with ANB Sensors, has introduced a next-generation self-calibrating pH sensor designed to transform long-term ocean monitoring. The newly developed sensor combines Teledyne Valeport’s engineering precision with ANB Sensors’ proprietary calibration-free technology, setting a new benchmark for reliability and performance in marine pH measurement. The innovation made its debut at Ocean Business 2025 in Southampton, UK. Historically, pH data has been acquired using glass electrode technology – valued for its accuracy but hindered by fragility, complex storage requirements and the need for frequent recalibration to mitigate reference electrode drift. These limitations often translate into increased maintenance costs and reduced operational uptime. The new Teledyne Valeport pH sensor overcomes these challenges with a self-calibrating mechanism that eliminates the need for manual recalibration, significantly reducing

TGS chooses Exail Gaps M7 USBL system to optimize offshore geophysical surveys

To strengthen the accuracy and efficiency of its offshore geophysical operations, energy data and intelligence specialist TGS has chosen the Gaps M7 USBL system from Exail. This compact, pre-calibrated positioning solution combines USBL and inertial navigation system (INS) technology to deliver reliable subsea tracking – from ultra-shallow environments to depths of up to 7,000 metres. With a 200° acoustic aperture, it enables true horizontal tracking for high-accuracy positioning, making it ideal for TGS’s demanding offshore surveys. Lightweight and pre-calibrated, the Gaps M7 ensures fast deployment, minimizing downtime and streamlining survey workflows. Its rugged design guarantees stable performance in harsh offshore conditions, supporting TGS in acquiring high-quality geophysical data while reducing project costs. “We needed a solution that would provide reliable, precise and high-elevation tracking of our magnetometer and sidescan sonar,” said Anders Landbø, director maritime performance and projects at TGS. “After testing other USBL systems without satisfaction, we tried Gaps and then decided to invest in this solution as it exceeded our expectations, offering ease of use and exceptional performance. Its pre-calibrated setup and high accuracy in shallow waters have significantly improved the efficiency and reliability of our offshore operations, and we are confident it will continue to enhance our geophysical surveys.”

TGS has selected the Exail Gaps M7 USBL system to optimize offshore geophysical surveys. (Image courtesy: TGS)

downtime and operational overhead. Engineered for durability and ease of storage, the sensor is ideally suited for extended deployments in demanding marine environments.

The new Teledyne Valeport pH sensor. (Image courtesy: Teledyne Valeport)

Deep takes over hydrographic training company

Skilltrade

OceanAlpha debuts L42 USV for enhanced offshore data collection

At Ocean Business 2025, OceanAlpha unveiled its latest maritime autonomy solution: the L42 uncrewed surface vessel (USV). The launch event marked the debut of a platform designed to meet growing industry demand for efficient offshore data collection, with practical innovations in endurance and payload flexibility. Equipped with a hybrid power system, the L42 USV offers an operational range of over 1,500km (eight days at four knots), minimizing the need for frequent retrieval during extended surveys. Its four redundant electric motors enhance stability, ensuring reliable performance across a wide range of sea conditions – from coastal zones to the open ocean. Engineered to streamline workflow integration, the platform supports standard survey instruments including multibeam echosounder, towed sidescan sonar, towed magnetometer, subbottom profiler and USBL positioning systems. Its onboard wetend payload lifters and towing system enable rapid configuration changes between hydrographic mapping, pipeline inspections and diversified scientific research missions.

On day one of Ocean Business 2025, OceanAlpha launched the vessel with a ceremony highlighting its operational readiness.

Deep has acquired Skilltrade, a well-regarded hydrographic training company, which will continue to operate under its established name as part of the Deep group. The company will maintain its focus on offering a comprehensive range of training programmes for the hydrographic and geophysical survey sectors. This acquisition highlights Deep’s ongoing commitment to the advancement of surveying, particularly in addressing the growing demand for skilled professionals in the hydrographic and geophysical survey industry. As the sector evolves, the need for expertise has never been more critical, not just for survey companies but across the broader maritime contracting industry. While Deep recognizes that the future of surveying relies on experts who can integrate emerging technologies with practical applications, equally important is the need to attract new talent to meet the increasing market demands. The ability to transfer knowledge and effectively train personnel is essential for upholding industry standards. Through this acquisition, Deep aims to support the sector’s continued development while expanding its service offerings and reinforcing its role as a trusted independent subcontractor.

Students participating in a hydrographic practice project as part of their training course at Skilltrade. (Image courtesy: Skilltrade)

Klein Marine Systems establishes Sonar Innovation Lab at University of New Hampshire

Klein Marine Systems, a global leader in sonar technology, has established the Klein Sonar Innovation Lab at the John Olson Advanced Manufacturing Center, University of New Hampshire (UNH). This milestone strengthens the ongoing collaboration between Klein Marine Systems and UNH, supporting the advancement of next-generation sonar technologies and marine exploration. Additionally, Klein has renewed its industry partnership agreement with UNH’s Center for Coastal and Ocean Mapping/Joint Hydrographic Center (CCOM/JHC) to demonstrate its commitment to promoting academic-industry partnerships that drive technological progress. As part of this initiative, Klein Marine Systems has loaned a high-end sonar system to CCOM, providing students with hands-on access to industry-leading technology while ensuring that the next generation of marine scientists and engineers will be better prepared for future careers in the field. “The University of New Hampshire along with the Center for Coastal and Ocean Mapping Joint Hydrographic Center are ideal partners providing key resources such as access to research vessels, test facilities and local engineering talent,” said Ted Curley, vice president and general manager of Klein Marine Systems. “We’re excited that the next generation of Klein sonars will be developed at our new Sonar Innovation Lab at the John Olson Center,” he added.

the collaboration between

advancements in nextgeneration

technology and marine exploration.

Introducing the SatLab HydroBoat 1200 MB: A Simpler USV Multibeam Solution

The HydroBoat 1200 MB combines a proven unmanned platform with the advanced HydroBeam M2 multibeam echosounder, delivering survey-grade results with minimal setup. It’s ready to survey within five minutes, featuring calibration-free deployment and real-time direct XYZ point cloud output — no post-processing or format conversion required.

Designed for efficient elevation mapping and underwater 3D scanning, it offers up to 7.5× the coverage of single-beam systems — ideal for inland and nearshore surveys. With an integrated Android-based interface and an all-in-one design, small teams can work faster, reduce costs, and confidently deliver high-resolution results.

The new product will be launched soon. Stay tuned and follow SatLab for updates.

Marian McCord, John Roth, Larry Mayer, Erin Bell and Ted Curley at the newly established Klein Sonar Innovation Lab at the John Olson Advanced Manufacturing Center, University of New Hampshire. This milestone reinforces

Klein Marine Systems and UNH, driving

sonar

Interview with Manon Larocque, Hydrographer General of Canada and Director General of the Canadian Hydrographic Service

Canada’s pioneering role in hydrography

By Wim van Wegen, Hydro International

Manon Larocque oversees hydrographic efforts across one of the most geographically vast and diverse maritime regions in the world. Here, she shares her perspective on Canada’s influential role in the international hydrographic community and the challenges – and opportunities – presented by the country’s complex marine environment. The conversation touches on how evolving technologies are reshaping the way that hydrographers work, the importance of digital transformation, and why CHS-led S-100 sea trials are a milestone in the adoption of next-generation standards. It’s a thoughtful exchange that offers insight into both the current state and future direction of hydrography in Canada and beyond.

Canada is one of the first countries worldwide to adopt the S-100 standard. Do you see this as a sign of Canada’s pioneering role in hydrography?

The Canadian Hydrographic Service (CHS) is Canada’s agency for charting Canadian waters. Canada has the longest coastline of any country in the world, with more than a third of its territory under water. As a maritime nation that borders three oceans – the Atlantic, the Arctic and the Pacific, oceans play a fundamental role in our

Canadian history, culture, economy and way of life from coast to coast to coast. Our rich maritime history of hydrography goes all the way back to 1883, when the first Canadian hydrographic survey was conducted. The urgent need for Canadian hydrography was recognized after the 1882 sinking of the passenger steamer Asia in Georgian Bay claiming 150 lives, which led to the Georgian Bay Survey, the precursor to CHS, being established.

Hydrography is a science that is continually advancing and, as such, CHS has always been an innovative organization. Through participation in the International Hydrographic Organization’s committees and working groups, CHS helps to develop, define and influence some of the standards. As we move to become fully integrated in a digital world, Canada continues to demonstrate a commitment to innovation.

Canada’s S-100 sea trials is a stellar example of CHS’ leadership in the implementation of new S-100 standards. As the first nation to offer the full S-100 Phase 1 package providing detailed navigational data such

Heading north from Coral Harbour. Des Groseilliers survey, August 2024.

Manon Larocque.

as water levels, currents, navigational warnings and high-resolution bathymetry, Canada is at the frontier of rolling out new S-100 products and services.

The IHO has approved Canada’s proposal to designate the St. Lawrence River as an international S-100 sea trial area starting in June 2025. What will this testing involve, and what are your expectations?

Endorsed by the IHO, CHS in collaboration with the Canadian Coast Guard (CCG) and others will host sea trials providing real-time S-100 data and services along the 350km stretch of the St. Lawrence Waterway, from 1 June to 30 November 2025.

We are opening up the trial to the international community and will be offering data free of charge for a limited period of time, where mariners and original equipment manufacturers (OEMs) will be invited to test the complete suite of S-100 route monitoring navigational services on the water or in a simulated environment, enabling them to evaluate system compatibility and identify opportunities for improvements before full deployment and legal use in 2026. The S-100 sea trials will allow participants to test multiple use cases, through which we will gather feedback that will be shared openly with the IHO Member States in order for us all to learn from this process.

The sea trial in the St. Lawrence Seaway is the culmination of many years of hard work by my predecessors and staff at CHS, working collaboratively with our partners both domestically and internationally.

Given Canada’s vast geography and environmental diversity, hydrographers in your country face unique challenges, such as frozen waters and drifting ice. Can you share some insights

into how your teams navigate these conditions?

Undertaking hydrographic surveys in the Canadian Arctic does bring with it some unique challenges for CHS. There is a short window each year in which it is possible to conduct our survey operations, generally from late July until the end of October. CHS works in close collaboration with the CCG – leveraging their icebreaking fleet – as well as the Royal Canadian Navy and dedicated private contracted charter vessels to collect data in the Arctic. In fact, six CCG icebreakers have been equipped with hull-mounted multibeam echosounders, which are key platforms used by CHS to undertake both dedicated and opportunistic surveys.

Surveying in the Arctic entails complex logistics and long lead times for planning. Flexibility is also important, as ice or weather conditions can sometimes dictate where and what type of surveys can be completed. CHS personnel require extensive training and must be equipped with protective gear such as survival suits.

Given the immense size of the Canadian Arctic (over four million km2 with 36,000 islands), CHS is also actively assessing and pursuing new technologies such as uncrewed survey vessels (USVs), which have the promise of being a ‘force multiplier’ for traditional vessel-based surveys. We also leverage remote sensing data to more accurately map shorelines and estimate depths via satellite-derived bathymetry.

With Arctic waters becoming increasingly ice-free, how pressing is the need for comprehensive seafloor mapping in the region – and what risks do current data gaps pose?

Charting in the Arctic is crucial for safety and efficiency of navigation, resource management and research. The vastness of the Canadian Arctic represents a significant challenge in and of itself. With climate change leading to faster melting ice in the north and the opening of new navigation routes, there is an increase in maritime transport

Levelling a 24-hour benchmark occupation on the Tasmania Islands, Nunavut. Des Groseilliers survey, August 2024.

traffic in the Arctic regions with corresponding growing demand for modern charts in new or previously largely uncharted areas. More accurate, real-time data is increasingly crucial to continue to support the growing demands of the maritime community.

CHS hydrographers are actively involved in surveying Canada’s coasts and inland waterways. What are some of the most complex or significant projects currently underway?

In addition to the regular programme of work for CHS regarding production, updating and maintenance of our hydrographic products, there are a few projects underway to note.

Digital transformation is about modernizing our traditional products and services to align with the global community’s move towards new standards as we enter a new digital era of marine navigation. As you can imagine, this is a major project. By transforming how we deliver products, we will provide near-real-time information into the hands of navigators, increasing safety as updated information of new hazards will be communicated more quickly and electronic navigation charts can be updated faster than traditional paper charts. These data-driven services will allow for more efficient shipping, supporting environmental and sustainability objectives.

Tied to digital transformation are the new S-100 products and services, a number of which are scheduled to come online in 2026. CHS’ Quebec region is ready to roll out new S-100 products and services, which we will be trialling during survey season 2025 (June–November 2025) in the St. Lawrence Seaway.

CHS received some federal funding to support the Oceans Protection Plan (OPP2). This funding is mainly being used to support two initiatives: i) Arctic charting (increasing surveys/coverage of low impact shipping corridors/high traffic areas in the Arctic) and ii) community

hydrography (working with coastal/First Nations communities on the use of hydrographic tools/data to support community needs).

Of course, we are also involved in the United Nations Convention on the Law of the Sea (UNCLOS). Working with Global Affairs Canada and Natural Resources Canada, CHS is gathering bathymetric data and conducting analysis to support Canada’s extended continental shelf in the Arctic.

Another project worth mentioning here is the Mackenzie River project. One of the significant challenges faced by CHS hydrographers is the need to keep products current in rapidly changing environments. While many coastal regions of Canada remain stable, others are dynamic and require regular updates to reflect ongoing changes – further exacerbated due to climate change. Due to its highly dynamic nature, the Mackenzie River has been selected as the first area in the country to test the integration of remote sensingderived products via a hybrid methodology that integrates both synthetic aperture radar (SAR) and optical data from satellites. The imagery analysis process also incorporates automated procedures that utilize AI to expedite the maintenance of products. This multifaceted approach aims to enhance the accuracy and timeliness of nautical product creation and maintenance, ultimately resulting in superior products that are better adapted to changing environments.

How do you manage to keep pace with the rapid technological advancements in hydrographic surveying?

CHS works with the international community to keep pace with the development of new technologies such as drones, satellitederived bathymetry, AI and uncrewed survey vehicles. Canada is an active participant in the IHO, supporting the Council and several working groups, and attends conferences to learn about the latest hydrographic science findings shared between academia, industry

Visit to the weather station in Eureka, Nunavut. Des Groseilliers survey, August 2024.

and government communities, share best practices and benefit from knowledge sharing.

Which recent technological innovations have had the most significant impact on the way CHS operates?

Over the coming decade, we should be moving to full S-100 implementation, meaning new route monitoring layers can be added over the electronic navigation charts and clients have access to a single maritime window (though single window is not a CHS lead, our products would be available via this window). Navigators have seamless information at their fingertips, with near-real-time updates of certain critical components, leading to more efficient route planning and less transit or idle time waiting to get into ports, which in turn reduces greenhouse gas emissions and potentially reduces costs for consumers.

Crowd-sourced bathymetry and innovative tools such as AI, drones, uncrewed vehicles and satellite-derived bathymetry are increasingly used as viable data sources, speeding up the process of collecting information leading to updated products and services. To align with these changes, the digital transformation of the organization is enabling it to become increasingly agile, investing in skills of the future with new training and recruitment approaches.

The digital transformation of hydrography has resulted in vast volumes of high-resolution data. How does CHS manage, process and share these datasets effectively?

CHS effectively manages, processes and shares vast volumes of high-resolution hydrographic data through a comprehensive approach that encompasses the full value chain. CHS utilizes centralized databases and cloud storage solutions for efficient data management, employs advanced automated processing tools and the rule of three scales maximum for optimal data handling, and removes duplication in publications such as sailing directions to enhance clarity. Additionally, CHS uses a national gridded scheme for organizing data, promotes transparency through open data platforms, and collaborates with governmental and international agencies to ensure data consistency and support joint initiatives. These strategies ensure stakeholders have access to accurate and reliable information for safe navigation, resource management and environmental protection.

The S-100 hydrographic data products and services require a near constant feed of information. To ensure the quality of data coming from new technologies or third parties, it must undergo validation and requires significant data storage, maintenance and mining capability. The potential of S-100 is significant but may not be maximized until these processes can be further automated or ‘trained’ with the use of AI and machine learning.

What does the future of the hydrographic profession in Canada look like? What skills will graduates require to meet the sector’s evolving needs?

The workforce of the future will need a combination of skills that include traditional technical and scientific skills such as hydrography, oceanography, GIS, geodesy and engineering combined with data managers and IT/AI experts to truly maximize the use of new technologies.

Manon Larocque was appointed Hydrographer General of Canada and Director General of the Canadian Hydrographic Service (CHS) in September 2023. Mrs Larocque has 26 years of experience in the federal public service, taking on management/executive roles in Global Affairs Canada, the Canadian Space Agency and more recently the Department of Fisheries and Oceans. In her current role, Mrs Larocque is chair of the US-Canada Hydrographic Commission, and leads Canada’s delegation to the IHO Assembly and the Arctic Regional Hydrographic Commission.

The success of CHS relies not solely on hydrographers, but a combination of skills. The future employee must be agile, creative, innovative and able to exert critical thinking: communicators and collaborators that can work in partnership with external stakeholders and the international community.

What initiatives are in place to raise awareness of hydrography among younger generations and inspire future professionals?

CHS leverages social media and outreach initiatives to highlight the important work that hydrographers do. At the international level, CHS proposed an Empowering Women in Hydrography project to the IHO to elevate women to leadership roles in hydrography. Some of our regional directors also visit academic institutions to raise the profile of CHS, presenting our work and type of work opportunities to inspire the next generation to pursue careers in STEM fields. We also participate/support student challenges organized in the context of the Canadian Hydrographic Conference every other year.

Is there anything else you would like to share with the international hydrographic community at this time?

Clearly, the context under which we work is changing rapidly. Factors such as technological advancements, the significant economic development in the north, and the need to protect the environment and ensure safety of navigators, in a context of fiscal restraint and increased security awareness – all encourage us to challenge our traditional ways of delivering products and services.

In the world of hydrography, the needs of our clients are evolving and the use of new, innovative technologies will transform our work as we move to a digital world. Establishing standards for data is of utmost importance, to enable interoperability of data and operational oceanography. The opportunities offered via new S-100 products and services are significant. I encourage anyone interested to take part in the S-100 trials in the St. Lawrence River this coming survey season.

About Manon Larocque

First Antarctica expedition of Schmidt Ocean Institute successfully completed

Schmidt Ocean Institute’s research vessel Falkor (too) has marked a major milestone with the completion of its first Antarctic science expedition. After a year of meticulous preparations, both the ship and crew embarked on a three-week journey, navigating the region’s challenging conditions to conduct groundbreaking research. The mission, which concluded in early January, pushed the boundaries of scientific exploration while fine-tuning operational strategies for future voyages.

“Operating our ship in the Southern Ocean marks a significant milestone in Schmidt Ocean Institute’s history,” said Eric King, senior director of maritime infrastructure.

“RV Falkor (too) performed exceptionally well, our crew gained tremendous knowledge and experience, and the expedition prepared us well for future explorations around this part of the global ocean in the coming decade.”

RV Falkor (too) is a certified Class C polar vessel, which means it is capable of operating in austral summer when there is light sea ice, also known as first-year ice. The ship received its polar certification from the International Maritime Organization (IMO) in October 2024 and was operationally supported by EYOS (Expeditions, Yachts, Operations, Support Services), an internationally known polar expedition organization. EYOS aided in mission planning, permitting and more. Two ice pilots also joined the expedition to ensure the vessel safely manoeuvred around icebergs, said King.

Eight dives to depths

The scientific operations included eight dives to depths as great as 3,918 metres using the remotely operated vehicle (ROV) SuBastian to assess biodiversity and explore vents and seafloor mapping. Ice pilots and crew transported scientists via small boats to places such as Joinville Island, off the northeastern tip of the Antarctic Peninsula, for marine mammal and sea bird research.

The ship’s satellite systems also livestreamed ROV dives, connecting the global

population with the Antarctic seafloor. The rare sights included icefish guarding their eggs, cold Antarctic seep environments characterized by bacteria feeding on chemical energy, and dense sponge and kelp outcrops in frigid -1°C water (about 30°F).

“For many seafarers and explorers, rounding Cape Horn, crossing the Drake Passage and sailing to Antarctica are bucket list items,” said Schmidt Ocean Institute captain Peter Reynolds. “It truly was a collaborative effort by the entire team and such an amazing experience to have safely navigated our way to the seventh continent in the name of advancing science.”

Into the Southern Ocean

The inaugural expedition to Antarctica, called Into the Southern Ocean, was a collaboration between Schmidt Ocean Institute and the National Geographic Society. As part of the Society’s Perpetual Planet Ocean Expeditions supported

by Rolex’s Perpetual Planet Initiative, a multidisciplinary cohort of National Geographic explorers conducted a comprehensive scientific examination –from sea ice to sea floor – of this critically important yet understudied marine ecosystem to advance conservation solutions in the Southern Ocean.

After one more Antarctica expedition in early 2025, RV Falkor (too) will spend the next four years primarily supporting research in the South Atlantic Ocean. “This was just the beginning of our journey into polar environments, and I am proud of our incredible crew and staff for our first successful voyage into the Southern Ocean,” said Schmidt Ocean Institute executive director, Dr Jyotika Virmani. “Our plan is to visit Antarctica multiple times over the next decade, supporting vital scientific research in parts of the ocean that may seem remote, but are intricately connected to the wellbeing of everyone on this planet.”

RV Falkor (too) navigated Antarctic icebergs on its first science expedition, conducting eight ROV SuBastian dives, sea ice operations and seafloor mapping. (Image courtesy: Mónika Naranjo-Shepherd)

How I accidentally became a multibeam trainer

By Jonathan Beaudoin, HydroOctave Consulting, Canada

Ever wondered how a chance turn can lead to a thriving global training career? Jonathan Beaudoin never set out to do multibeam training differently – but somehow, it just evolved that way. Two years and 50+ courses later, his distinctive, hands-on style is gaining traction worldwide. In this story, he reflects on how it all started, what makes his approach click, and why his focus is always on making trainees better by the very next day.

Looking back, I didn’t set out to do multibeam training differently, it just happened that way. I don’t know why I’m doing it differently, I just am. I don’t necessarily believe that it should be done differently but I’ve found my groove doing it this way and I think it’s working. Plus, people tell me it’s very effective.

How, you ask? What’s different? I have a singular vision: I’m trying to make each trainee a better version of themselves the very next day they return to their job; that’s my North Star that guides everything.

It all started with a phone call from my client, Steve. I did data analysis and troubleshooting work for him and his

team but this time he wanted something different: multibeam training. He asked cautiously, as if he was worried I wouldn’t be interested. I was still in my first year as a consultant and had promised myself that I’d say yes to as much as possible, to be open-minded about growing outside my comfort zone. I hadn’t even thought about doing training when I decided to become a consultant. I had no lecture material to lean on and it had been a very long time since I had taught at universities earlier in my career. I paused, then decided to say yes.

My experience as a product manager in my previous job made me ask him some clarifying questions, including: ‘Why do you need training for the team?’, ‘What

kind of problem are you trying to fix?’, ‘Tell me more about your team’s background and knowledge level’ and ‘Why are you asking me? Aren’t you able to find training solutions?’

He went on to tell me that he had junior staff who were making rookie mistakes in the field. They’d leave the site with data that didn’t meet specification, or they’d run the patch test lines incorrectly. He said he wanted them to understand the job specifications and which controls on the multibeam are critical to pay attention to.

He also said that existing trainings from hardware and software vendors taught you ‘how’ but not ‘why’. He said that formal education in schools took too long, and didn’t cover the practicalities. Graduates are left with the classic gap between book smarts and field smarts. He also mentioned that there are high-level short courses out there but they’re too theoretical for someone very new in their career. Trainees would be left wondering ‘How do I apply this?’ when back on the job. He said there’s a real gap in the market for solutions that fill in the holes between all those different types of training and education. He had been a student of mine back in our university days, he remembered my teaching style and he felt that I could probably figure something out to solve this.

I’m glad I asked him those clarifying questions as it forced me to start with a

Figure 1: Sample survey specifications from six clients in the offshore renewables sector.

blank slate and a very clear goal: to give these young surveyors the practical knowledge they needed in as little time as possible with a high degree of learning and retention. I received example survey specifications from Steve then set out to develop lecture material towards this (see Figure 1).

From the table in Figure 1, I broke down the job of being a skilled multibeam operator into the three components that are most specified on any mapping job (see Figure 2). For each of these components, I tried to answer ‘Why do clients specify this?’ and ‘How do you achieve it?’ These three components are (1) resolution – sometimes you need to localize and detect targets of a certain size, (2) hit count – sometimes your client has exact needs in terms of measurements per square unit of area and (3) accuracy –sometimes your client has a maximum level of uncertainty they are willing to tolerate.

I then went through the sonar controller software interface and made screen grabs of everything, I scoured the operator’s manual, and I created lecture materials to highlight which controls had a role in any one of the three aspects. I then put together simple and highly understandable drawings that told the story of what is happening behind the scenes but with only a very modest amount of math, theory or complexity. The idea was to give a taste of why, such that they had more understanding but were not overwhelmed with theory that wouldn’t be of any help in a practical sense. If a topic or idea had no practical way of making them better surveyors, I didn’t talk about it. That could be done later in their careers.

The outcome was course material that met Steve’s goals – training that offers practical, actionable insights to help hydrographic surveyors make confident, informed decisions in the field. Given that the course is completed in just a few days, I called it a ‘multibeam crash course’.

The course went very well. At the end, Steve thanked me and said: ”‘You know you’re really good at this and other people are looking for this kind of training. Let me give you a few contacts.”

I try to create a fun and safe learning environment where there’s room for the ‘dumb questions’

Things blossomed from there. It has been just over two years since that first course, and I have now given this exact course or variants of it over 50 times. It has grown from a three-day course to five days. I have added more content to cover all the major multibeam vendors, as well as practical group exercises that we do while in class with survey calculators that I provide (see Figure 3). I offer the course privately to single teams but more and more I am giving open enrolment workshops with a mix of participants. This year, I am going global to Australia and Portugal with plans in the works for Brazil and Japan. The idea is to offer this several times per year globally.

With the large number of iterations in such a short period, there’s a lot of opportunity to improve from the lessons I’m learning along the way. I’ve shared a few below.

1. Bridge – I need to meet trainees where they are at with their knowledge level and understand their backgrounds so that I can build a bridge from their knowledge to mine. It also helps me understand if I have some expertise I can leverage. There are always other experts in the room.

2. What & why – I always ask trainees what they want to learn and why they want to learn it. I get them to identify their own learning

Figure 2: Foundational view of topics in the multibeam crash course.

Figure 3: Working through a practical exercise in a group setting.

outcomes, the skills they want to walk away with. We share those in a group setting. I identify trainees that have skills that others are looking for and I leverage their know-how, experience and expertise to help me lift others. Everybody gives some knowledge. It’s almost like I’m a coach and I’m building a team.

3. Discussion-based learning – I need to make trainees comfortable with discussion-based learning. I try to keep the class size small enough to build comfort, familiarity and trust. I drop the rank and formality, introduce myself as JB and not Dr Beaudoin, and sneak in a few Dad jokes. I get everyone in the room to contribute with real world examples, experiences, challenges and successes. I let their curiosity and questions determine what theory to cover when they want to go beyond the course material, which usually entails a visit to the white board. I try to create a fun and safe learning environment where there’s room for the ‘dumb questions’. They’re handing me teachable moments; I make sure to use them.

4. Mentoring – I sometimes need to help employers and trainees understand that someone needs to own the job of mentoring after the training.

It has been a very busy two years and I’m very excited to bring this style of training to more and more people. Even though I found my way to this type of work quite by accident, I can’t imagine doing anything else at all now that I’m here.

About the author

Jonathan Beaudoin is a hydrographic consultant and selfproclaimed multibeam nerd. He earned a PhD in Marine Geomatics from the University of New Brunswick (UNB) in Fredericton, Canada, with a focus on multibeam data processing and analysis. Following his time at UNB, he spent nearly four years as a researcher at the Center for Coastal and Ocean Mapping at the University of New Hampshire, further building on the work he developed during his doctoral studies. He then joined QPS, where he spent eight years as chief scientist and head of product management, and from 2017 to 2022 also served as managing director. Today, he runs his own hydrographic surveying consultancy, helping surveyors and solution providers get the most out of their hydrographic endeavours.

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Kongsberg Discovery equips year-long research voyage with latest technology

Kongsberg Discovery has played a pivotal role in transforming the 111-year-old Statsraad Lehmkuhl into a modern research vessel for the next leg of the One Ocean Expedition, which set sail from Bergen, Norway, on 11 April. Measuring nearly 100 metres, the iconic three-masted barque is Norway’s largest sailing ship. It now carries a comprehensive suite of Kongsberg Discovery technology to support scientific exploration of remote and ecologically significant marine environments, including the storied Northwest Passage.

Among the onboard systems are 75kHz and 300kHz acoustic Doppler current profilers (ADCPs), EK80 echosounders, a sophisticated hydrophone cluster and the Seapath GNSS-aided inertial navigation system. Data captured at sea will be processed and shared daily via Blue Insight, Kongsberg Discovery’s advanced platform for ocean data management and analytics. Additional equipment includes weather stations, water samplers, situational awareness and motion reference units, plus various sensors designed to expand the vessel’s research capabilities and contribute to a deeper understanding of the world’s oceans.

Collecting a wealth of data en route

The One Ocean Expedition 2025–2026 is a 12-month voyage encompassing 26 ports across three continents. It will see a crew featuring seasoned scientists, eager students and key stakeholders crossing the Atlantic Ocean, the Mediterranean, the Arctic, the Pacific and the Caribbean. En route, the team will collect a wealth of data to help ascertain ocean health, monitor marine ecosystems and assess the impact of climate change, building both knowledge and awareness of pressing issues.

“It is a great honour to be supporting this crucial expedition with our cutting-edge solutions,” says Martin Wien Fjell, president of Kongsberg Discovery. “The ship will work as a unique data acquisition platform, empowering insights in often remote and

little-understood environments, such as the Northwest Passage, while gathering invaluable information about the broader state of ocean health.

“Our systems are perfectly suited to the tasks ahead, performing with proven reliability, optimal precision and highquality results in even the most demanding conditions. We’re looking forward to setting sail, while also helping the students set sail on their careers as the next generation of ocean scientists and explorers. We believe major discoveries await.”

Technology package

Kongsberg Discovery’s innovations will be put to work on several key assignments, including measuring ocean currents with the ADCP, to help understand how marine life is affected by ocean movements, and recording underwater noise using hydrophones, to ‘listen’ for pollution and monitor marine mammals such as whales.

“The Statsraad Lehmkuhl is an incredible vessel, but to meet the ambitious expedition goals it needed a major technology upgrade,” comments Haakon Vatle, CEO and expedition leader, The One Ocean Expedition. “We’re immensely grateful to Kongsberg Discovery and the Kongsberg Group for their commitment to tailoring a technology package that will allow us to shine light on the depths and unlock a level of understanding that, we hope, can benefit the entire world.”

Statsraad Lehmkuhl is one of the world’s largest, oldest and most elegant square-rigged ships still in full operation year-round. (Image courtesy: One Ocean Expedition)

The One Ocean Expedition sets sail during One Ocean Week in Bergen, calling in at ports including Reykjavik, Nuuk (Greenland), Cambridge Bay (Canada), Seattle, La Paz (Mexico), Cartagena (Columbia), Cadiz and Dublin. During its stop in Nice, France, vessel team members will participate in the 2025 UN Ocean Conference. Statsraad Lehmkuhl will return to Bergen in April 2026, in time for next year’s One Ocean Week.

Efficient data compression and visualization software for multibeam echosounders

Surfing the big data wave

Water column data acquired by multibeam echosounders (MBES) imposes large requirements on disk storage and data transfer, so it is typically logged only during specific times, a practice that poses the risk of missing interesting targets. Furthermore, huge data volumes from both bathymetry and water column data can lead to considerable burdens for the operators during long surveys. MBES data is often compressed using standard solutions such as Zip or 7-Zip, but these can be computationally heavy for a relatively modest size reduction. To overcome this, we developed FAPEC, a high-performance data compression software, now supporting MBES data. We also present FARSHY, a fast visualization and analysis tool to streamline quick checks on the heavy water column files.

Space technology for marine echosounders

DAPCOM’s FAPEC data compression software was originally designed for satellites such as ESA’s Gaia, the billion-star surveyor, where onboard computing, storage and downlink capabilities are extremely limited. Later, FAPEC was enhanced with improved performance and additional algorithms to better adapt to a wide variety of file formats and data characteristics. In collaboration with Kongsberg Discovery and the Marine Geosciences Research Group of the University of Barcelona (UB), FAPEC was adapted to accommodate the .all, .wcd, .kmall and .kmwcd (KMall) formats from Kongsberg’s

EM MBES systems, and more recently it has been integrated into Kongsberg’s Seafloor Information System (SIS) to provide automated file compression once the logging files have closed. FAPEC is being further extended to other formats and vendors.

FAPEC runs on Windows (including a graphical user interface, WinFAPEC), as well as on macOS and Linux, and it supports ARM processors. Its C, Python (fapyc package) and Java API allows for integration in third-party software. FAPEC rapidly examines the files to be compressed, determining the best algorithm and configuration for each of them. It supports tabulated text files (such as CSV or point clouds), multidimensional time series and multispectral images, to name a few. Therefore, rather than a universal data compressor, FAPEC is adaptive and versatile, allowing a much more efficient use of resources.

Figure 1: Screenshot of WinFAPEC while compressing several files on a standard laptop.

On MBES datasets kindly provided by Kongsberg and Fugro (who have started using FAPEC on their vessels), FAPEC demonstrated superior performance: it achieved better compression than 7-Zip, while running 50 times faster and using 30 times less memory. Depending on the echosounder and scenario, FAPEC further reduced the file sizes (compared to 7-Zip) up to 10% for water column data, and up to 23% for combined bathymetry and water column data.

Beyond data compression

By default, FAPEC runs in lossless mode, meaning that the original files can be exactly recovered. However, for .wcd and KMall files, it also provides several lossy compression options, meaning that the quality of the data is slightly degraded to achieve a better compression. For KMall bathymetry (soundings), it allows for an instrumentally lossless operation, just removing the measurement noise. The seabed image samples can be quantized at a level indicated by the user, and can even be mostly removed if not needed. A similar approach is provided for older (.wcd) water column files.

For KMall water column data, besides sample quantization, FAPEC also provides a smart lossy mode, which examines the sample values and removes those below a given percentile. This makes it possible

to keep most of the features in the water column (including sub-bottom data) while vastly improving the compression ratio. In the specific example shown in the FARSHY screenshots, the combined bathymetry and water column KMall file is 933MB, which is reduced to 410MB in lossless mode, and just 154MB with these lossy options. When adequately adjusted, water column files can become even smaller than bathymetry files while retaining most of the relevant nformation.

FAPEC achieves these results by knowing the data format and examining the values. It can provide basic data analytics on the fly, namely small CSV-like text files with a digest of the file contents. For example, it generates a water column features index, which aims to indicate sudden changes in the scene such as those created by gas seeps, fish shoals or

Figure 3: Screenshot of FARSHY showing gas seeps in the water column (left) and the along-track view (top right). (Data courtesy: Fugro)

Figure 4: Same water column file as in Fig. 3 after lossy compression by FAPEC, reaching a compression ratio of six while showing an even clearer view of the gas seeps.

Figure 2: Plots obtained with Python from on-the-fly basic data analytics provided by FAPEC, from soundings (left: beam width, depth and coordinates) and water column data (right: depth and features index).

shipwrecks. In the same KMall example file, this digest is just 391KB (105KB compressed), and with a simple Python script we can create interesting plots similar to those shown in Figure 2.

Water column visualization made simple and fast

Scanning multiple water column files to look for potential features can be slow and cumbersome with the usual processing tools, although they are obviously essential when high accuracy and detailed analysis are required. DAPCOM’s FARSHY offers an appealing solution for rapid water column examination, as it allows for a fast loading and exceptionally fast browsing of numerous pings in a line file. Its simplicity is also attractive for students and newcomers. Like FAPEC, it inherits some aspects of space technology – namely, the visualization of multiband satellite imagery.

FARSHY is fully implemented in Java, meaning that it can be used in Windows, macOS and Linux. It currently supports Kongsberg’s KMall water column files (either raw or compressed with FAPEC), generating the usual fan-shaped view for individual swaths or in a stacked mode. Additional features include an along-track view, sample value histograms and a spectrum-like visualization of all sample values for all swaths at given positions of the water column. GPS coordinates, bottom location and depth are also calculated based on the associated bathymetry. In collaboration with Kongsberg Discovery, we have implemented a feature that makes it possible to send target GPS coordinates directly to SIS, where they appear in the geographic display as user objects.

Click here for a video showing a quick demo of the FARSHY software.

Another interesting feature of FARSHY is its mixed colours view, which can also be invoked from the command line, enabling batch processing of all KMall or KMwcd files within a directory. This functionality allows users to generate a single image per line, providing a quick overview of features present in the water column. Besides static images, FARSHY can also generate GIF movies from a selected range of swaths.

Click here for an example GIF movie from the water column file with the gas seeps.

About the authors

More information dapcom.es

Jordi Portell (PhD in Applied Physics, UPC 2005) is CTO and co-founder of DAPCOM Data Services and deputy technology director at ICCUB (UB), where he has been working on ESA’s Gaia since 2000, among other science projects.

David Amblas is associate professor at the UB and head of the MAPSUB lab. An expert in submarine cartography and underwater acoustics, his research focuses on oceanography-geology interactions in key climate regions such as the Mediterranean, Southern Ocean and North Atlantic.

Colleen Peters is the product manager for mapping software at Kongsberg Discovery. She has over 15 years of at-sea experience collecting and managing scientific data.

Remote Sens. 2022, 14(9), 2063

Intl. Jour. Remote Sens. 2017, 39(7), 2022–2042 http://dapcom.es/ https://www.mdpi.com/2072-4292/14/9/2063 https://www.tandfonline.com/doi/full/10.1080/01431161.20 17.1399478

Conclusion

We have presented new software tools to streamline the handling and analysis of large datasets from MBES systems, with a particular focus on water column files. FAPEC offers excellent compression ratios at outstanding speeds, making it suitable even for ARM-powered autonomous vehicles and remote vessels, where optimizing the communications channel is critical. Its unique combination of lossy compression (or noise removal) and basic data analytics capabilities paves the way for continuous and systematic MBES water column acquisition. FARSHY provides rapid, portable visualization and analysis capabilities for KMall water column files, including batch processing, SIS integration and fast swath browsing.

Figure 5: Mixed colours view of FARSHY for the same water column, from the original lossless file (left) or the lossy-compressed file (right).

Multi-partner effort reveals full extent of reefs offshore south-east US

Mapping the largest known coldwater coral reef habitat

By Derek C. Sowers, Larry A. Mayer, Giuseppe Masetti and Kasey Cantwell

More than a decade of mapping and exploration work by federal, academic and private-sector partners has uncovered what has been deemed the largest deepsea coral reef habitat mapped to date. Spanning an area of over 10,000 square miles (26,064km2, about three times the size of Yellowstone National Park in the US), this underwater seascape of cold-water coral (CWC) mounds is located about 100 miles offshore the south-east United States coast in a region called the Blake Plateau.

The reefs were mapped at depths ranging from 655 to 3,280 feet (200 to 1,000 metres), beyond the sunlit euphotic zone. Unlike tropical coral reefs that rely on sunlight and photosynthesis, corals at these depths filter particles out of the water for food. The largest nearly continuous expanse of reef mounds extends 310 miles (500km) from Florida to South Carolina and at some points reaches 68 miles (110km) wide. Data also revealed several additional subregions on the plateau that also contain cold-water coral mounds. Across the entire expanse of the Blake Plateau, mapping analysis revealed 83,908 individual peak features – providing the first estimate of the overall number of potential cold-water coral mounds mapped in the region to date. The full results of this study, Mapping and Geomorphic Characterization of the Vast Cold-Water Coral

Figure 1: Bathymetric terrain model synthesis grid of the Blake Plateau CWC mound study region. The white polygon represents the core area (2,400mi2 / 6,215km2) of very dense and nearly continuous CWC mound features in the largest CWC province on the plateau. The black dotted line polygon represents the maximum extent of continuous CWC features in the largest province (10,063mi2 / 26,064km2). The solid black polygon shows the existing boundaries of the Stetson-Miami Deep Water Coral Habitat Area of Particular Concern. At this scale, individual coral mound features are not discernible. (Figure adapted from Sowers et al., 2024)

Mounds of the Blake Plateau, have been published in the journal Geomatics (Sowers et al., 2024).

The Blake Plateau: a globally important hotspot for cold-water corals

Large cold-water coral mounds were first documented offshore the south-eastern US in the 1960s (Stetson et al., 1962). Since then, extensive research has been conducted by regional experts to discover new mounds throughout the Blake Plateau and to document the ecological importance of these habitats (e.g. Reed et al., 2006; Ross and Nizinski, 2007). Fisheries managers have used this information to protect known coral areas from physical damage. The recently completed mapping effort in the region builds on this foundational work by revealing the full extent and characteristics of these important deep-sea coral mound features.

The most common reef-building coral in the region is Desmophyllum pertusum (previously referenced in the literature as Lophelia pertusa). Healthy living corals of Desmophyllum pertusum appear white in colour. The white in this case does not indicate coral bleaching (unlike shallow-water corals).

Coordinated mapping to assess the full extent of Blake Plateau reefs

Multibeam sonar systems have proven effective in mapping complex mound and reef habitats remotely from surface ship hull-mounted sonars, with resolution directly related to the depth of the seafloor and the angular resolution of the multibeam system.

Approximately 50% of US marine waters have still not been mapped in detail with multibeam sonars. The US has a national strategy for mapping, exploring and characterizing US Waters (NOMEC), and this project is a great example of the benefits of this work and the partnerships necessary to complete such a massive undertaking. Mapping work and analysis on the Blake Plateau was completed as part of a coordinated, multi-year ocean exploration campaign involving NOAA Ocean Exploration, NOAA Ocean Exploration Cooperative Institute partners Ocean Exploration Trust and the University of New Hampshire, the Bureau of Ocean Energy Management, Temple University and the U.S. Geological Survey, with contributions from Fugro, the NOAA Deep Sea Coral Research and Technology Program and the South Atlantic Fishery Management Council.

The study area is nearly the size of Florida, and stretches approximately from Miami, Florida, to Charleston, South Carolina. Data from 31 separate multibeam sonar mapping surveys completed between 2003 and 2021 were synthesized into a seamless bathymetric terrain model with 35m grid resolution to accommodate all the data sources. The largest areas were covered by 17 expeditions led by NOAA Ocean Exploration on NOAA Ship Okeanos Explorer, five mapping surveys completed by NOAA Ship Nancy Foster, two expeditions led by the DEEP SEARCH project on NOAA Ship Ronald H. Brown and R/V Atlantis, and one mapping survey that Fugro vessel Brasilis completed for NOAA Ocean Exploration. The majority of multibeam sonar mapping completed on the Blake Plateau was conducted as part of the Atlantic Seafloor Partnership for Integrated Research and Exploration (ASPIRE) and the DEEP SEARCH: DEEP Sea Exploration to Advance Research on Coral/Canyon/Cold seep Habitats campaigns.

Figure 2: Dense thicket of the cold-water coral reef habitat found on the Blake Plateau in the Atlantic Ocean. (Image courtesy: NOAA Ocean Exploration, Windows to the Deep 2019)

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Figure 3: Example of what CWC mounds can look like in multibeam sonar bathymetry data. This oblique 3D perspective figure shows the bathymetry of the Richardson Mounds subregion of the Blake Plateau. Image created in QPS Fledermaus software with 4× vertical exaggeration. (Figure from Sowers et al., 2024)

Classifying the geomorphology of the seafloor

Beyond synthesizing all the mapping data on the Blake Plateau and identifying the largest continuous areas of CWC mound distribution, this study applied a repeatable and objective approach to characterizing the geomorphology at the scale of individual mound features as well as the region as a whole. An objective geomorphic landform classification of the region was derived from the bathymetry using the bathymetry- and reflectivity-based estimator for seafloor segmentation (BRESS) method (Masetti et al., 2018). The following landform types were selected to meet the study goals while enabling the classification of a continuous geomorphic map of the region: flat, slope, valley, ridge and peak.

A mound is composed of peaks, ridges and slopes. The study analysed 6,081 images of the seafloor from 23 submersible dives on the mound features, and found that coral rubble was the dominant substrate component within the peak, ridge and slope landforms explored, thereby validating the interpretation of these bathymetric features as cold-water coral mounds. Once peak features were classified from the bathymetry, ArcGIS Pro software was used to quickly quantify the overall number of peaks and calculate the areal coverage of

each landform type. Cumulative areas were calculated for each of the five geomorphic landform classes: peaks (159mi2 / 411km2), valleys (1,389mi2 / 3,598km2), ridges (1,406mi2 / 3,642km2), slopes (8,912mi2 / 23,082km2) and flats (39,709mi2 / 102,848km2).

The vertical relief of CWC mounds was deemed to be an important defining characteristic to quantify across the entire study area and within each subregion. Therefore, five metrics were calculated pertaining specifically to mound relief within each of these areas: minimum, maximum, mean, median and standard deviation. The complex geomorphology of eight subregions was characterized qualitatively with geomorphic ‘fingerprints’ and quantitatively by measurements of mound density and

vertical relief. The median mound relief for the entire study region was 52 feet (16m), with individual mound features ranging 10–741ft (3–226m) above the adjacent seafloor. These results demonstrated that CWC mound spatial distribution, density, vertical relief and morphology varied greatly among subregions of the Blake Plateau.

The importance of the Blake Plateau cold-water corals

Cold-water coral reefs play an important role in recycling nutrients in the deep sea to support the surrounding ecosystem, sequestering carbon and providing a complex structure and hard substrate that provides a habitat for many associated corals, sponges, invertebrates and fishes (including commercially important species). They are therefore essential in supporting biodiversity, ocean health and recreational and commercial fisheries in the south-east US and beyond.

Cold-water coral habitats are slow-growing, long-lived and fragile, making them particularly vulnerable to physical damage from human activities that disturb the seafloor. Threats include trawling, hydrocarbon and mineral exploration and production, and cable and pipeline placements. The ecological importance and vulnerability

how

classified into five different landform types using BRESS. The bathymetry and vertical relief of a typical mound feature is shown on the left, and the automatically classified landform features from BRESS (draped onto the bathymetry) are shown on the right. (Figure from Sowers et al., 2024)

Figure 4: A 3D view example of

input bathymetry data is

of these deep-sea reefs has resulted in increased national and international efforts to map, characterize and protect them.

Even before the new mapping data was acquired, in response to improved information from many researchers in the region on the nature and distribution of CWC resources on the Blake Plateau, the South Atlantic Fishery Management Council (SAFMC) designated the Stetson/ Miami Terrace Deep Water Coral Habitat Area of Particular Concern (HAPC) in 2010 to protect the seafloor in this area. The designation prohibits the use of bottomcontact fishing gear (bottom longline, bottom and mid-water trawl, dredge, pot and trap), anchoring by fishing vessels and possession of deep-water coral. Most coral mounds documented in this research are located within the protected area, but new mapping data revealed that 9.3% of mound features (7,782 individual mounds) are located outside the existing protection area boundary. All the information collected and presented in this study is public information and available to support informed management decisions.

Conclusion: implications for characterizing cold-water corals and other marine habitats

The global distribution of CWC species remains poorly understood, given that most of the global deep ocean is yet to be

Figure 5: Oblique perspective 3D views of a section of the core area of dense mounds in the largest expanse of corals. Bathymetry of mound features in metres (upper panel). Geomorphic landform classification draped onto the bathymetry (lower panel). Note the delineation of the white peak features from the rest of the CWC mounds (inset) to enable the enumeration of mounds. Figure created using QPS Fledermaus software with 7x vertical exaggeration. (Figure from Sowers et al., 2024)

mapped or explored. The region of the Blake Plateau with the most dense and abundant coral mounds is directly underneath the massive marine food conveyor belt of the Gulf Stream current. This suggests that there may be other parts of the world with large cold-water coral mound ecosystems waiting to be discovered, associated with large and consistent ocean currents. The methods used in this study provide a pragmatic

As more of the seafloor is mapped to modern standards, newly generated datasets will be ripe for comprehensive geomorphic analysis

Acknowledgments

This research was made possible by years of dedicated investments in expedition planning and staff resources from NOAA Ocean Exploration. The data collected for this study represents countless hours of field data collection at sea by the dedicated officers, crew members and scientists of the vessels from which data was obtained.

standardized approach for identifying, characterizing and quantifying CWC mound-forming habitats and could be applied to other CWC provinces to enable more direct comparisons among geographically diverse settings.

As more of the seafloor is mapped to modern standards through initiatives such as Seabed 2030 and NOMEC, newly generated datasets will be ripe for comprehensive geomorphic analysis. This

Figure 6: Geomorphic landform overview map with analysed CWC subregions labelled A–H, each with unique morphologies that were apparent after classification. Note how the landform map provides a strong immediate visual contrast between flat areas and complex terrain. Black circles show the location of submersible dives with video footage of the seafloor used to ground-truth substrates. (Figure from Sowers et al., 2024)

About the authors

Derek Sowers is the mapping operations manager for the Ocean Exploration Trust. He has a PhD in oceanography from the University of New Hampshire, and has participated in oceanographic expeditions spanning remote areas of the Arctic, Pacific and Atlantic Oceans.

Larry Mayer is a professor and director of the Center for Coastal and Ocean Mapping at the University of New Hampshire. His research deals with sonar imaging and remote characterization of the seafloor, advanced applications of 3D visualization to ocean mapping and mapping in support of Law of the Sea and paleoceanography, particularly in the Arctic.

Giuseppe Masetti has worked as a senior hydrographic consultant at the Danish Geodata Agency since 2019. After having served with the Italian Navy as a hydrographic officer, Giuseppe Masetti joined the UNH’s Center for Coastal and Ocean Mapping as research faculty.

Kasey Cantwell is the operations chief for NOAA Ocean Exploration, responsible for mission operations aboard NOAA Ship Okeanos Explorer She oversees telepresence-enabled exploration, deep-sea mapping and multidisciplinary ocean expeditions worldwide.

study demonstrates the value of applying an objective automated terrain segmentation and classification approach to geomorphic characterization of a highly complex CWC mound province. Manual delineation of these features in a consistent repeatable way with a comparable level of detail would not have been possible. As inevitably larger regions of the oceans become mapped and explored, and the technological capability to map extensive seafloor features in high resolution with autonomous underwater vehicles expands, the importance of semi-automated classification approaches will only increase. Sole reliance on manual delineation and expert judgment is not a practical approach as datasets increase in size and complexity. Whereas traditional methods of geomorphological characterization can make it difficult to reproduce results across large ocean regions, this study highlights the benefits of applying an automated terrain analysis approach using repeatable methods and standardized terminology.

Towards a more continuous, consistent and justified establishment

Integrating the continuous hydrographic datum and DEM for maritime boundary delimitation

By Mohd Faizuddin Abd Rahman, Ami Hassan Md Din, Mohammad Hanif Hamden and Mohd Razali Mahmud

The delimitation of maritime boundaries plays a significant role in preserving a country’s sovereignty and jurisdiction. Their determination justify a country’s rights, allowing coastal states to prevent illegal infringements and trespassing by foreign vessels. A proper delimitation of maritime boundaries also helps to preserve a country’s commercial fishing rights, marine navigation and shipping routes and underground resource exploration, such as that of minerals, oil and gas. The maritime baseline is established based on a combination of maritime basepoints, and represents the low-water line along the coast. There are three types of maritime baseline: normal, straight and straight archipelagic. The United Nations Convention on the Law of the Sea (UNCLOS) has established several maritime zones with their respective distances from the coast that are applicable to all coastal states, as illustrated in Figure 1.

To this day, the maritime basepoint is still determined based on a limited number and sparse distribution of tide gauge stations along the coast. However, as previous studies show, the resulting hydrographic datum is only valid in coastal areas around the tide gauge stations, and is inaccurate at distances a few tens of kilometres away from the tide gauge stations and in offshore areas. Such limitations raise uncertainty in the establishment of the maritime basepoints and baselines, particularly when there is a large distance between tide gauge stations. Another challenge regarding the uncertainty in maritime boundary delimitation is the overlapping claim by neighbouring states, particularly in the territorial sea (TS) and exclusive economic zone (EEZ) regions. Unresolved maritime boundaries can heighten tensions and increase the potential for military confrontations, as states may engage in aggressive stances.

Another issue is legal ambiguities, where inconsistent enforcement practices may

result from varying interpretations of international law, particularly the UNCLOS. There are also environmental concerns, as disputed areas may suffer from a lack of attention to environmental protection efforts, worsening problems such as pollution and habitat destruction. Coastal development is another issue. Natural changes in coastlines due to natural processes can lead to outdated baselines, complicating urban planning and coastal infrastructure development. Technological challenges also arise as advancements in mapping and surveying may outpace legal frameworks, leading to disputes over which data should be used to establish baselines. Last but not least is the issue of international cooperation: uncertainty can hinder regional cooperation on issues such as search and rescue operations, environmental protection and joint resource management.

Variety of data sources

A continuous hydrographic datum (CHD), which integrates the hydrographic datum from multiple sensors, can mitigate this

problem. In this study, a CHD was developed based on the hydrographic datum derived from tide gauge stations, multi-mission satellite altimeter (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3, GEOSAT Follow On (GFO), ERS-1, ERS-2, ENVISAT-1, Cryosat-2, SARAL, Sentinel-3A and Sentinel-6), satellite-derived bathymetry, a hydrodynamic model accessible via Tide Model Driver (TMD) and shipborne bathymetry using single-beam echosounder (SBES) and multibeam echosounder (MBES) data. The data sources used to develop the CHD are shown in Figure 2.

Common reference surface

Several CHDs have been developed in the past decades, comprising bathymetry with reference to the Ellipsoid (BATHYELLI, 2005), Vertical Offshore Reference Frame (VORF, 2009), Continuous Vertical Datum for Canadian Water (CVDCW, 2010), Vertical Reference Frame for the Netherlands (NEVREF, 2018), Saudi Continuous Chart Datum (SCCD, 2019) and the Malaysia Vertical Separation (MyVSEP) model (2022), as illustrated in Figure 3.

However, the derived hydrographic datum for each sensor must first be referenced to a common reference surface, which is either World Geodetic System 1984 (WGS84) or Geodetic Reference System 1980 (GRS80) globally, or the local mean sea level (MSL). This article proposes the utilization of the local MSL as a reference surface, meaning that the derived lowest astronomical tide (LAT) and highest astronomical tide (HAT) from every sensor are referenced to MSL, denoted as LAT_MSL and HAT_MSL. As a way of integrating the derived hydrographic datum from every sensor, this study proposes using a spatial interpolation technique (with a grid size of ≤ 10km). Methods such as ordinary kriging, minimum curvature Spline, inverse distance weighting (IDW) and many other spatial interpolation techniques are recommended.

Comprehensive foundation

Several reasons justify the establishment of a CHD. First, the dynamic ocean environment is constantly changing due to tides, currents and climatic variations. A CHD can accommodate these fluctuations, providing real-time data that enhances navigational safety. Second, with the increase in maritime activity with the rise of shipping traffic, fisheries and offshore energy exploration, the demand for accurate hydrographic data has surged. Thus, CHD allows for updated information that supports efficient route planning and resource management. Third, climate change plays a significant role. Rising sea levels and changing weather patterns demand adaptive management strategies. A CHD can assist in monitoring these changes, providing essential data for climate research and policy-making. Fourthly, the CHD can be utilized in several applications. A CHD provides

up-to-date depth information, which is crucial for safe navigation, particularly in shallow or congested waters. It also plays a key role in environmental monitoring as accurate hydrographic data supports the management of marine ecosystems, enabling better assessments of habitats and biodiversity. Fifthly, in infrastructure development, a CHD aids in the planning and maintenance of maritime infrastructure such as ports, bridges and offshore platforms. Lastly, in the disaster

Figure 1: UNCLOS maritime zones (NOAA, 2023).

Figure 2: Data sources for developing a continuous hydrographic datum.

response, real-time data from CHD can enhance preparedness and response strategies for natural disasters such as tsunamis and hurricanes.

Digital elevation bathymetry model

To pinpoint the location of the lowest water line along the coast for the delimitation of maritime boundaries, the established CHD must also be integrated with a high-accuracy digital elevation model (DEM), for example obtained using light detection and ranging (Lidar) or interferometric synthetic aperture radar (IfSAR), or an open-source DEM obtained using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topography Mission (SRTM), Advanced Land Observing Satellite World 3D (ALOSW3D) or TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) data. In a previous study by Indonesia, the Digital Elevation Bathymetry Model (DEBM) was developed in 2022 to update the position of maritime basepoints and baselines, particularly for the region without bathymetry data. Its data sources comprise elevation and bathymetry data. The elevation data used includes the National Digital Elevation Model (DEMNAS), which was developed based on IfSAR (5m resolution), TerraSAR-X (5m resolution) and ALOS PALSAR (11.25m resolution). The spatial resolution is 0.27 arcs per second. The reference surface for DEMNAS is Earth Gravitational Model 2008 (EGM2008). As for the bathymetry data, the tidal data was acquired from Indonesian National Bathymetry Data (INBD), which is based on the General Bathymetric Chart of the Ocean (GEBCO) combined with local bathymetry data. In addition, the DEBM employs SBES and satellite-derived bathymetry (SDB) data using four bands: blue (0.49μm), green (0.56μm), red (0.665μm) and near-infrared (0.842μm) images from Sentinel 2A. It also incorporates hourly tide gauge station data from the Mailepet station (1° 33’ 49.7” S and 99° 11’ 49.2” E), obtained from the Geospatial Information Agency (BIG) from 2011 to 2022.

The DEBM is one of the most important examples of integrating bathymetry data from multiple sensors and DEM for the delimitation of maritime boundaries. There are several advantages to integrating

About the authors

Mohd Faizuddin Abd Rahman, PhD graduate at the Faculty of Built Environment and Surveying, UTM. His research is entitled ‘Near-Seamless Tidal Datum from Multi-Sensor Data for Maritime Boundary Delimitation.’

Ami Hassan Md Din, associate professor at the Faculty of Built Environment and Surveying, UTM. His research interests encompass geodesy, marine geodesy, geoid modelling, satellite positioning, highprecision positioning, radar remote sensing, hydrography, physical oceanography and tidal modelling.

Mohammad Hanif Hamden, senior lecturer at the Faculty of Built Environment and Surveying, UTM. Expertise in marine geodesy, geomatics engineering and hydrography. Dedicated educator and researcher with a focus on advancing geospatial sciences.

Mohd Razali Mahmud, former chair of FIG Commission 4 (Hydrography) from 2019–2022. Also a former member of the FIG/IHO/ICA International Board on Standards of Competence for Hydrographic Surveyors and Nautical Cartographers (2001–2014).

Figure 3: Development of a continuous hydrographic datum.

the CHD and DEM. To begin with, there is the accurate depth and elevation data. By combining real-time hydrographic data with highresolution elevation models, decision makers can achieve a more comprehensive understanding of the underwater terrain and water column dynamics, leading to more accurate boundary definitions. Next is the adaptability to environmental changes. A CHD accounts for fluctuations in sea levels and tidal changes, while the DEM provides static topographical data. Their integration allows for the adaptive management of boundaries in response to climate change and shifting oceanographic conditions. Another advantage is the enhanced spatial analysis. By using geographic information systems (GIS), combined datasets can facilitate complex spatial analyses, including identifying natural features that serve as boundaries, such as underwater ridges or valleys. Lastly is the legal and diplomatic clarity. Accurate and updated data can help resolve disputes over maritime boundaries by providing clear, objective evidence based on scientifically valid measurements.

Conclusion

This article emphasizes the importance of developing a CHD as well as its integration with a DEM for the delimitation of maritime boundaries. It also summarizes and reviews nations that have successfully developed a CHD using multiple sensors, including BATHYELLI, VORF, CVDCW, NEVREF, SCCD and MyVSEP. This article also highlights several DEMs (Lidar, IfSAR, SRTM, ASTER, ALOSW3D and TanDEM-X) that can be used for integration with the CHD. In conclusion, the proposed can improve the conventional approach

of only using a limited number of sparsely distributed tide gauge stations, leading to a more continuous, consistent and justified establishment of maritime basepoints and baselines for coastal states.

An insight into terminology and practices

Airborne Lidar and photogrammetric accuracy

By Huibert-Jan Lekkerkerk, technical editor, Hydro International

Over the years, many articles on airborne Lidar and photogrammetric surveys have been published – primarily in GIM International, a sister publication of Hydro International, but occasionally in the latter as well. As technical editor, one standard question I ask the authors is ‘What was the accuracy?’. The responses vary not only in value, but also in how accuracy is quoted. The definition of accuracy is not only relevant to articles but also in contract specifications. This article gives an overview of terminology and methods, using the ASPRS and IHO specifications as a basis.

Many people (and contract specifications) use the term ‘accuracy’ without fully defining it. In statistics, the term ‘accuracy’ is not well defined and could indicate different things to different people. In statistics terminology, it is based around three main types of errors: systematic errors, random errors and blunders. Blunders (sometimes also called ‘spikes’) are errors so large and/or obvious that they are usually removed from the dataset before further statistical processing and thus not relevant to specifications.

Systematic error or bias

The systematic error or bias is an error that follows a certain rule. When the rule is known, the error can be removed. The geodetics are an important systematic error in all surveys. Incorrect geodetic parameters will lead to a shift of all the coordinates surveyed. The survey may still look correct

between objects, but is in fact completely in the wrong place. Once we figure out the size (rule) of a systematic error, the results can be corrected.

Many specifications consider the systematic error to be ‘near zero’ after careful calibration and installation. However, no matter how well the installation and calibration were performed, a small residual error usually remains. Such residual errors can be found in small offset errors between, for example, GNSS and sensor, but also in the boresight calibration for Lidar, the inertial measurement unit (IMU) alignment or the camera parameters in photogrammetry.

Random error

The random error is usually stated as the error which remains after all blunders and

systematic errors have been removed. A random error is mainly influenced by the environment and instruments. The GNSS is a good example of this. Due to satellite movement, atmospheric conditions and receiver electronics, each position will deviate to a certain amount from the true, average, value.

In surveying, we often consider the random error to be ‘normally distributed’. This effectively means that the error follows a pattern which only seems random over a short amount of time. If we take enough measurements, we should find that the

Figure 2: Definition of ASPRS accuracy classes (NVA = Non-vegetated, VVA = Vegetated).

Figure 1: A-priori horizontal error computation for Lidar. (Image courtesy: ASPRS)

average of all measurements is equal (or very close) to the true position, provided there are no systematic errors present (and all blunders have been removed). Another important aspect of the normal distribution is that we can predict how far the errors will deviate from this average. This is called the ‘uncertainty’ of the measurement and is generally stated in terms of the standard deviation (or sigma, σ) of the measurements.

In the normal distribution, this uncertainty relates to how many measurements are within a certain distance of the average. Take for example an RTK dGNSS system with a standard deviation of 10mm + 1ppm. The definition of this random error indicates that there is a fixed error (10mm) and one that is distance-dependent (parts per million [ppm] or mm/km). At 10km from the base station, this computes to 10 + 1 x 10 = 20mm. The normal distribution now tells us that we may find (rounded) that 68% of all our measurements are within one standard deviation or 20mm from the average, and that 95% (rounded) of our measurements are within two standard deviations or 40mm from the average. 95% is also called the ‘confidence level’ as it indicates how many of our measurements are within this value of two standard deviations from the average.

Root mean square error

In the real world, it is almost impossible to measure the true average – not only due to small residual errors, but also because the true average (real position) is also measured and thus not precisely known. Therefore, many specifications use a term like root

mean square error (RMSE). This is effectively a combination of the (unknown) systematic error or bias and the (unknown) standard deviation as found in a real survey, when the results are compared to independent ground control points (GCPs) for example. RMSE is comparable to the standard deviation, and would even be the same if there would be no bias in the measurements. However, as both the GCP and the measurements have their own (residual) error, the RMSE is generally slightly more pessimistic than the standard deviation itself. The RMSE (after removal of blunders) is usually what is meant by ‘accuracy’ in a specification.

The RMSE indicates 68% of the measurements as it is based on the one standard deviation (sigma) level. Vertical accuracy is quoted as a 2RMSE value by the 2014 Positional Accuracy Standards for Digital Geospatial Data of the American Society for Photogrammetry and Remote Sensing (ASPRS), so at a 95% confidence level. For Lidar bathymetry, which follows the standards of the International Hydrographic Organization (IHO) (namely its S-44 Standards for Hydrographic Surveys), the term ‘total vertical uncertainty’ (TVU) is equivalent to the 2RMSE value.

Positional accuracy

Whereas the vertical accuracy is a one-dimensional number, positional accuracy consists of two dimensions: longitude / X / E and latitude / Y / N. An RMSE could be quoted for both dimensions, but most clients are more interested in ‘how far’ the measured point is from the real coordinate. This distance between the true and

Figure 3: A-priori computation in AMUST software for multibeam echosounder against IHO S44 Special Order.

measured position is the distance root mean square (DRMS). The DRMS can be computed from the standard deviations in both horizontal directions and indicates a circle within which the real-world position should fall. The confidence level for the DRMS differs from the RMS(E) value in that 1DRMS represents a 63-68% confidence level (or around 66% on average) and 2DRMS indicates 95-98% confidence. Standards differ in how they approach positional accuracy, with ASPRS using a 2RMSE value for the X and Y directions separately as well as a ‘range’ 2RMSEr equivalent to 2DRMS,

Figure 4: Top: Coastal bathymetry of St. Thomas, US Virgin Islands, mapped using Lidar and presented in false colour (purple indicating deep areas, orange indicating shallow). Land areas are shown with satellite imagery. Left: Highaltitude topobathymetric Lidar data collected by Woolpert. Right: Illustration of how multisensor data is efficiently collected with real-time quality control. (Image courtesy, respectively: USGS, Woolpert/USACE/JALBTCX, and Teledyne Geospatial)

while the IHO uses the term ‘total horizontal uncertainty’ (THU) which effectively is a 2DRMS value. The confidence levels are not identical to a single RMSE but could be considered similar enough for practical purposes.

Accuracy in specifications

With accuracy defined, we now need to turn to specifications. As stated, both the IHO and the ASPRS have standards which are applicable to Lidar (both) and photogrammetric (ASPRS) surveys. The IHO works with ‘orders’ of accuracy for safety of

navigation surveys and has a selection matrix that can be used to create specifications for all other types of surveys. The ASPRS defines ‘classes’ of accuracy in a similar way but distinguishes between vegetated and nonvegetated land. The latter is of course less of an issue under water.

Both standards focus on the random error component. The IHO states that systematic error should be minimized but does not quote a number. The ASPRS standards advise the user to limit systematic error to 25% of the overall 2RMSE values.

Ultimately,

the accuracy of a survey can only be determined after the survey data is

processed

About the author

Huibert-Jan Lekkerkerk is technical editor of both GIM International and Hydro International, freelance hydrographic consultant and author of multiple other publications on GNSS and hydrography. He is also principal lecturer in Hydrography at Skilltrade (Cat B) and the MIWB (Cat A). Besides lecturing, he is a PD candidate at the MIWB.

Figure 5: IHO S44 bathymetric orders, also applicable to Lidar bathymetry.

A-priori uncertainty

Ultimately, the accuracy of a survey can only be determined after the survey data is processed. However, it is unwise to embark on a survey if it can be predicted that the required accuracy cannot be met with the intended survey design and sensors. The test whether a chosen configuration will meet the requirements using the survey design is called the ‘a-priori uncertainty estimation’ or simulation.

The tools to compute this uncertainty are relatively limited. The ASPRS includes a simple mathematical model in its specification, but this is limited to positional accuracy and only contains a few parameters. Based on an internet search, there is some software available, albeit more for planning than for a-priori uncertainty estimates. Similarly, for bathymetric surveys, there are some software packages for a-priori computation for multibeam echosounders, but these do not include bathymetric Lidar. A-priori models for photogrammetric surveys have not been found.

A-posteriori accuracy

While a-priori estimates are scarce, accuracy determination after the survey is commonplace for Lidar and photogrammetry. All major software vendors include statistical tools which give a variety of statistical parameters including computed accuracy. What is important to realize is that most parameters relate to the so-called ‘internal’ reliability or relative accuracy of the results. That is, they describe how measurements are related to other measurements in

the same survey. They generally do not represent systematic errors (which are part of the external reliability or absolute accuracy) very well.

External reliability, including systematic errors, can be tested by having independent (extra) testing points. These are like GCPs but should not be part of the original adjustment of the data like regular GCPs. They should preferably be measured using an independent and different technique. This also means that they should not be based on corrections from the same (RTK) base station but should, for example, be derived from RINEX data processing or land survey techniques. Ideally, some of these test points are supplied by the client as part of the specification. This is to prevent systematic errors in, for example, a base station setup to propagate in both the control as well as the original measurements. The combination of internal and external reliability can demonstrate the RMSE (or THU/TVU) values for the overall survey accuracy.

Conclusion

Accuracy is not very well defined. Using terminology like systematic error and random error or RMS(E) makes it clearer what is meant. A measurement can only be called accurate if the requirements for systematic error and random error have been met. The final results should include tests for internal and external reliability of the data. To prevent survey results that do not meet the specifications, an a-priori uncertainty estimation can be performed.

Autonomy in action

Robotic intelligence for subsea cable inspection

By Blair Thornton, University of Southampton, UK

Everyday life around the world depends on a global network of over 500 subsea cables that silently carry 95% of all international data [1]. These cables stretch more than 1.4 million kilometres across the ocean floor and are critical to the functioning of the internet, financial systems and government communications. But every year, 200 to 300 faults are reported. Most are caused by fishing gear and ship anchors, though abrasion and geological activity also contribute. All can disrupt essential services.

For example, in October 2022, both subsea cables to the UK’s Shetland Islands were damaged, leaving homes and businesses cut off, unable to access the internet or make financial transactions for several days. While various strategies aim to improve the resilience of this infrastructure, robotic systems can play a role through regular inspection and condition monitoring. However, this comes with significant technical challenges.

Challenges for robotic inspection

Near the shore, in water depths up to 2,000 metres, subsea cables are typically buried to protect them from anchors and fishing gear. Although cable routes are planned to avoid hazards, rocky seafloors – where burial is not possible – are sometimes unavoidable. Additionally, underwater currents can shift sediments over time, exposing cables that were previously buried. In areas where such risks are foreseen, alternative protective measures, such as stronger armouring or rock placement, are used. Beyond 2,000 metres, burial becomes too expensive and the risk from human activity is lower. Here, cables are laid directly on the seabed and are thinner – typically under 25mm in diameter.

Physically inspecting exposed cable segments is difficult for several reasons. First, there is uncertainty about the cable’s exact location. During installation, ocean currents can push cables off course by

5–10% of the water depth. Over time, further movement may occur due to seabed currents, landslides or accidental contact. These cables are also thin and hard to spot, and effective inspection requires sub-centimetre resolution. This is further complicated by the high cost of offshore surveys and the lack of GNSS underwater, which makes navigation challenging. Even with state-of-the-art sensor-aided inertial navigation, position errors typically build up at about 1% of the distance travelled. Acoustic tracking systems from the surface also have an error margin of about 1% of the vehicle’s depth.

Putting this into perspective, even in relatively shallow waters of 2,000 metres depth, the positional uncertainty of an undisturbed cable can be up to 200 metres. An underwater vehicle covering 100km in a day might experience position errors of around 20 metres with continuous surface tracking, or as much as one kilometre using only its onboard sensors. And these are bestcase figures – uncertainties only increase with depth.

The core challenge for autonomous cable inspection is that the combined uncertainty of both cable routes and vehicle navigation

1: Left: Subsea communication cables in shallow coastal areas are typically armoured and buried to reduce the risk of damage. In deeper water, where risks are lower, cables are thinner, with diameters less than 25mm, and lie exposed on the seafloor. Right: A section of 25mm cable exposed on rocky seafloor, demonstrating some of the challenges for automated detection.

Figure

Figure 2: Top: The Smarty200 AUV being deployed during a cable tracking survey. Bottom: Underside view showing key components. Three thrusters provide precise manoeuvring and altitude control. The rear section’s downward-facing camera captures seafloor images, illuminated by strobes in the forward wings. A second camera just ahead of it detects sheet laser projections on the seafloor for millimetric-resolution scanning. Acoustic sensors at the front of the vehicle measure altitude and velocity to support inertial navigation. An acoustic transponder and Iridium antenna enable underwater tracking and communication, with GNSS and satellite connectivity available at the surface.

exceed the narrow field of view of the high-resolution sensors needed for cable detection and inspection. This makes the traditional pre-programmed waypoint-following approaches commonly used by autonomous underwater vehicles (AUVs) ineffective. Additionally,

the large volumes of high-resolution data collected during inspection make manual analysis labour-intensive and prone to error.

Addressing challenges with intelligent autonomy

To tackle these challenges, engineers at the University of Southampton and Sonardyne International developed real-time methods that allow AUVs to autonomously detect and track cables and report key findings remotely – without the need for any human intervention. Field trials using the camera-equipped Smarty200 AUV demonstrated the system’s effectiveness (Figure 2). The system integrates three core capabilities:

Cable detection: Smarty200 uses machine learning to detect cables in real time from camera images [2]. The AUV flies between 1.5 to 3m above the seafloor, using acoustic sensors and its vertical thruster to maintain altitude. The system captures millimetre-resolution, strobeilluminated images and laser-scanned micro-bathymetry to map the cable and surrounding terrain in 3D (Figure 3). The system can detect cables across a variety of seabed types, automatically generating waypoints relative to the cable path to maintain tracking.

Map-guided navigation: The AUV starts with a rough map of the cable path, using it to automatically generate zig-zag search patterns that cover the estimated positional uncertainty of the map. When it detects the cable, it updates an internal probabilistic map that reflects the most likely cable path based on its observations. If the AUV loses its cable tracking – due to burial, or detection and trajectory errors – it uses the updated map to resume searching around the most likely area. Search boundaries are generated using physics-based ‘catenary models’, which estimate the plausible region where the cable might be if disturbed, while maintaining consistency with the accumulated observations.

Figure 3: Laser-scanned bathymetry and strobe-illuminated imagery collected by AUVs. The panels show a diverse range of seafloor substrate types and varying cable appearances. The bottom-centre panel shows a region where a remotely operated vehicle had previously landed near a scientific cable observatory. (The images shown were gathered during the Schmidt Ocean Institute’s Adaptive Robotics expedition [FK180731].)

Figure 4: Left: Experimental setup, with a section of communication cable laid across diverse seafloor substrates, including areas with partial burial and rock occlusion. A cable signal repeater model was attached to the cable for later use as a remote query target. Transponders provided groundtruth cable locations, but they were not used by the AUV. The AUV was given an initial cable map (blue line), intentionally offset from the true cable location, with uncertainty bounds covering the actual cable. Top right: Results of one of the dives, showing the AUV completing a round trip and observing over 70% of the cable length, including the repeater model. Bottom right: Remote summary generated by the AUV at the end of the dive, transmitted wirelessly before physical recovery, along with query-prioritized observations (see Figure 5).

Rapid reporting: High-resolution AUV camera surveys can generate hundreds of gigabytes of data, traditionally requiring physical recovery of the vehicle and downloading of data via a tether. Smarty200 avoids this by using self-supervised machine learning to generate compact observation summaries that can be remotely transmitted. Operators can provide the AUV with feature representations extracted from reference images (called queries) before, during or after a mission, and the AUV computes compact summaries of the images it captures based on their similarity to these [3]. Geotagged image similarity metrics and a subset of the most similar images are compressed and sent over low-bandwidth satellite or acoustic links. In recent trials, a 146GB cable dataset was reduced to just 188kB – a ratio of 1:800,000 – allowing transmission in about 20 minutes via Iridium satellite.

These methods work together to enable robust, fully autonomous cable inspection. The system does not require perfect detections. Instead, it updates a probabilistic cable path map to centre search patterns around the most likely path if the cable is buried or detection fails. Physics-based models keep the AUV within a likely corridor and summarized image reporting provides rapid and flexible over-horizon awareness of relevant observations before the vehicle is recovered.

The system was tested in shallow-water field trials using a section of deep-sea cable provided by the British Telecom Group. The test site featured a range of seafloor types to evaluate the system’s robustness, and multiple tracking experiments were performed. Figure 4 shows results from one of these, where the AUV began its mission by searching around the initial cable route map (which was offset from the actual cable) in a zig-zag pattern and made initial detections. Although the AUV temporarily lost track of the cable at

several points, by updating its internal cable map to be consistent with its observations, it was able to successfully reacquire the cable each time. When detection errors led the AUV away from the cable, it realized it was no longer detecting the cable and returned to the most likely path according to its updated map. The observation summary (bottom right of Figure 4) was generated in response to a query focused on the repeater (a device used to boost signal strength within the cables). The AUV assessed the similarity of each image to the query, where the outlines indicate the most similar

References

[1] Clare, M., Yeo, I., Bricheno, L., Aksenov, Y., Brown, J., Haigh, I., Wahl, T., Hunt, J., Sams, C., Chaytor, J., Bett, B., & Carter, L. (2022). Climate change hotspots and implications for the global subsea telecommunications network. Earth-Science Reviews, 237, 104296. https://doi.org/10.1016/j.earscirev.2022.104296

[2] Yamada, T., Prügel-Bennett, A., Williams, S., Pizarro, O., & Thornton, B. (2022). GEOCLR: Georeference Contrastive Learning for efficient Seafloor Image Interpretation. Field Robotics, 2(1), 1134–1155. https://doi.org/10.55417/fr.2022037

[3] Yamada, T., Prügel-Bennett, A., & Thornton, B. (2020). Learning features from georeferenced seafloor imagery with location guided autoencoders. Journal of Field Robotics, 38(1), 52–67. https://doi.org/10.1002/rob.21961

[4] Bodenmann, A., Jones, D. O. B., Phillips, A. B., Templeton, R., Sherif, R., Fanelli, F., Newborough, D., & Thornton, B. (2025). Remote awareness of image quality for multi-week shorelaunched AUV surveys. IEEE Transactions on Field Robotics., 2, 147–164. https://doi.org/10.1109/tfr.2025.3529435

Figure 5: Left: Operator interface during trials, showing dataset summaries that were generated and wirelessly transmitted by the AUV before physical recovery. Right: Images prioritized by the AUV as visually similar to the repeater model, which was used as a query. The top row shows the images at their original quality, and the bottom row shows the compressed versions that were transmitted by the AUV and received. The complete AUV-generated summary, including the geotagged metrics in Figure 4 (bottom right), was 188kB in size – small enough to be sent via the global Iridium satellite network in around 20 minutes.

images that it selected and transmitted at the surface. Figure 5 shows some examples of original and compressed versions of images transmitted during the trials. Key features are preserved despite the compression, supporting operator awareness for decision-making.

Looking ahead

The technologies demonstrate a path towards full autonomous

About the author

Blair Thornton is Professor of Marine Autonomy at the University of Southampton, UK, based within the Faculty of Engineering and Physical Sciences, with an adjunct post at the Institute of Industrial Science at the University of Tokyo, Japan. His work centres on advancing autonomous marine robotics, sensing technologies and intelligent systems to drive forward ocean SCIENCE.

inspection of exposed subsea communication cables. Further work is needed to explore compatibility with other high-resolution sensing modalities, including the integration of multiple sensors, and verify robustness over longer and more complex cable routes. While the Smarty200 is a capable demonstrator, real-world inspections will require deeper-diving AUVs with greater range and endurance. Recent multi-week, 1,000km shore-launched seafloor camera surveys – using the National Oceanography Centre’s Autosub Long-Range AUV and the BioCam imaging system – demonstrate that such extended operations are already technically feasible [4].

*data stream delay measured in milliseconds

Save Time

Data automatically cleaned during acquisition

Reduced post processing delivers final data fast

Demonstrating the power of integrated hydrographic equipment

Depth of burial survey of natural gas pipelines

A successful depth of burial (DOB) survey of natural gas pipelines crossing the Columbia River near Portland, Oregon, hinged on the high-resolution capabilities of the NORBIT WINGHEAD i80S Long Range multibeam system. This advanced equipment, featuring integrated Applanix Oceanmaster INS/ GNSS and an AML sound velocity sensor, played a pivotal role in capturing the detailed bathymetric data needed to guide and verify the sub-bottom profiling effort.

Working in tandem with the NORBIT system, an Innomar medium-100 parametric subbottom profiler was deployed to detect the buried pipelines and determine their depth below the riverbed. The survey area – located in a stretch of the Columbia River with depths ranging from 5 to 15 metres – was mapped using several parallel survey lines aligned with the river’s flow.

The NORBIT PORTUS pole was used to mount the sonar SBP over the side of the vessel to ensure optimal data acquisition. To complement the setup, the sound velocity profiler was used to collect accurate water column data, ensuring reliable acoustic performance.

Combined approach

This combined approach proved effective in a challenging riverine environment, with the NORBIT system providing the precise

bathymetric context needed to interpret the sub-bottom data and confirm the pipelines’ positions and depths. The result was a comprehensive and dependable survey, demonstrating the value of integrating cutting-edge multibeam and sub-bottom profiling technologies.

The Innomar medium-100 system is a portable high-power and high-resolution sub-bottom profiler. It utilizes non-linear acoustics, which provides a narrow sound beam for low frequencies and very short transmit pulses without ringing. This ensures excellent vertical resolution and high ping rates, suitable for object detection. The system consists of a transducer (over-the-side, bow or moonpool mountable) and a transceiver (19” with 9 HE) containing transmitter, receiver and a control PC running MS Windows for setup, interfacing and data storage. The primary high frequency is 100kHz (for bathymetry measurements) and the secondary low frequency is user-adjustable during operation from 4–15kHz (for penetrating sediments). The sound beam is as narrow as three degrees (valid for both the high and low frequencies) and actively stabilized for transmission and reception in real time. The system can be operated in water depths of 1–2,000m. Depending on the water depth, the ping rates can be as high as 40 pings per second.

The WINGHEAD i80S LR is a compact, fully integrated multibeam survey system with an up to 600m range performance offering 0.5×0.9° beam widths at 400kHz and 1.0×1.8° at 200kHz. The sonar is frequency agile from 200–700kHz and generates 1,024 dynamically focused beams per ping. The IMU is tightly embedded within the sonar head. NORBIT’s steerable transmission technology provides full motion stabilization (roll, pitch and yaw) to ensure uniform sounding coverage in dynamic sea states. Dual swath provides up to 2,048 beams, allowing higher sounding density and reduced survey time. The system weighs 8.0kg in air and connects to a compact topside unit via a single cable, allowing rapid mobilization.

Installation

The Innomar medium-100 transducer was mounted over the side on NORBIT’s survey vessel SheHorse using the NORBIT PORTUS mounting pole. The transceiver was rapidly mobilized, connected to the INS/

Innomar transducer mounted on NORBIT PORTUS pole.

bathymetry, seismic sections and the picked and connected pipeline locations.

GNSS with a network cable and configured via the NORBIT GUI. The INS/GNSS provides RTK-corrected position, roll/pitch/heave/ heading data for the sub-bottom profiler for real-time beam stabilization, heave correction and time stamping. The Innomar medium-100 requires no calibration prior to the survey. The speed of sound was set to 1,500m/s, and all given depth values are related to this velocity. The acoustic parameters were a transmit frequency of 8kHz (low frequency channel) and a signal length of 125µs (the length of a single 8kHz sinus cycle) with a recording range window of 5–25m below the transducer (providing a ping rate of about 25 pings per second).

Subsurface findings and riverbed dynamics

Three natural gas pipelines cross the Columbia River near Portland: two in parallel, each about 16 inches in diameter, and a third 14-inch line further south. The riverbed in this area is made up of sandy sediments,

shaped into ripples and dunes of varying size by strong, shifting currents. These dynamic conditions lead to a highly complex and continuously changing subsurface environment.

While the parametric sub-bottom profiler offered penetration depths of up to 10m, the survey focused on the upper layers (about 1–4m below the riverbed), where the pipelines are located. The short transmit pulses of the parametric system enabled a vertical resolution of approximately 10cm –fine enough to resolve individual sediment layers and clearly identify the buried pipelines in this challenging setting.

Data processing and visualization

The acquired data was processed using ISE, Innomar’s proprietary software, which is designed for handling parametric subbottom profiler data. The data can also be exported to the industry-standard SEG-Y format, for further analysis in any compatible third-party processing environment.

Since the system applies band-pass filtering during acquisition, the data typically requires no additional filtering or complex seismic processing. Interpretation is straightforward: hyperbolic reflections – commonly associated with buried objects such as pipelines – are visually identified by the operator, relying on the clarity of the raw acoustic signal rather than automated detection algorithms. The detected hyperbolic reflectors are picked with a mouse and exported as XYZ ASCII data, which is easy to import into any GIS

application or third-party software for mapping or visualization. QPS Fledermaus software was used to generate a 3D representation of the acquired MBES dataset, the vertical 2D seismic sections and the picked pipelines. Pipeline diameters are not shown to scale in the 3D view, just the top of the pipelines, so the hyperbolic features in the seismic sections remain visible.

Conclusion

The Innomar medium-100 parametric sub-bottom profiler proved to be a highly effective tool for measuring the DOB of pipelines and cables. Designed with practicality in mind, the system is compact and portable, making it well-suited for deployment from small survey vessels using over-the-side mounting.

Its flexibility extends beyond physical setup. The profiler interfaces easily with existing NORBIT multibeam systems or can be paired with standalone INS/GNSS units, allowing it to fit seamlessly into a range of survey configurations. What also sets the system apart is its efficient data workflow, as there is no need for extensive seismic processing.

More information

https://norbit.com/product/norbitwinghead-i80s/

https://innomar.com/innomarflyer/innomar-medium-100.pdf

Seismic section with hyperbolic reflections from the pair of pipelines buried at about 4m below the riverbed.

Aerial view of Columbia River (c. 750m wide) with an overlay of MBES-acquired bathymetry and SBP survey lines.

3D data representation of MBES-acquired

From seabed to showcase: exploring the best of Ocean Business 2025

In early April, the global ocean science and technology community descended on Southampton in unprecedented numbers for what proved to be the largest and most dynamic edition of Ocean Business to date. The National Oceanography Centre (NOC) played host to over 10,650 attendees – a 23% increase compared to the 2023 edition – as visitors from more than 80 countries convened for three days filled with groundbreaking innovation, major product launches and lively quayside demonstrations.

The expanded exhibition space and bustling dockside were alive with energy as deals were struck, new collaborations were formed and long-standing relationships were reaffirmed. From the outset, the enthusiasm was palpable. For Graeme McGhee of Scorpion Oceanics, it was “the best one yet.” Stuart Howard, founder of Kuro Animation, described it as “head and shoulders above other expos,” while Chris Wallace of Verlume emphasized the quality of engagement: “So many visitors from the very beginning and amazing conversations on all three days.”

The ocean’s storied past

The event opened with a powerful reminder of the ocean’s storied past, as keynote

and

speaker Mensun Bound captivated a full audience with an account of the 2022 international mission to locate Ernest Shackleton’s legendary ship, Endurance As director of exploration on the Antarctic expedition, Bound described the moment the team spotted a distinct shape 3,000 metres beneath the surface. “It was obviously something man-made,” he recalled. “And the only man-made thing in the Weddell Sea was Endurance.” The ship, astonishingly well preserved after 117 years frozen in ice, had been located with the aid of Saab Seaeye Sabertooth ROVs and elite subsea specialists. It is highly recommended to read more about the search for Endurance in the recent article Making subsea history by locating Endurance, available on the Hydro International website.

A wave of innovation

Day one brought another headline moment when Teledyne unveiled what it described as the world’s smallest and highest-performing fully integrated autonomous navigator. Marketing manager Guy Frankland was thrilled with the reception: “We couldn’t have asked for a better show launch… we’ve had so many existing and new contacts coming onto the stand.”

The show was rich with announcements. Planet Ocean revealed a collaboration with

Sonardyne International, integrating three gold-standard instruments from its partners – Sea-Bird Scientific, Sequoia and 4H-Jena. Geo Acoustics attracted global attention with its new sidescan sonar, receiving enquiries from Dubai to Italy. Meanwhile, RS Aqua shared news of a new UK distribution agreement with US-based SRS for its Fusion Hybrid ROV and described the event as a welcome chance to reconnect: “Still riding the wave after catching up with our partners, customers and old and new faces!”

With over 350 exhibitors and more than 180 hours of training sessions, live demos and classroom workshops, the scope of the event was unmatched. Attendees explored a wide array of innovations – from R3Vox’s Voxometer, which chairman Jens Steenstrup likened to a multibeam system “on steroids,” to Tritonia’s Hydrophis, hailed as a revolution in underwater survey data analysis.

Read the full version of this story here: www.hydro-international. com/content/news/from-seabed-toshowcase-ocean-business-2025

Ocean Business 2025 attracted a recordbreaking 10,000 visitors from 80 countries, who convened for three days of groundbreaking innovation, major product launches

lively quayside demonstrations.

We proudly present our premium members, the ambassadors of tomorrow's hydrography!

Will you be next?