The integration of Exail’s DriX uncrewed surface vehicle (USV) with Exail’s Sams 150 advanced synthetic aperture mapping sonar represents a breakthrough in marine survey technology. This combination offers an unprecedented level of efficiency, accuracy and endurance in seabed mapping. As the first deployment of its kind, this innovative pairing was recently operated in the Gulf of Mexico, in a collaboration between Exail and David Evans & Associates Inc. (DEA) for the National Oceanic and Atmospheric Administration (NOAA) Office of Coast Survey, demonstrating its potential to transform hydrographic survey operations.
By leveraging advanced technologies such as multibeam echosounders (MBES) and imagery from a synthetic aperture mapping sonar, the DriX is capable of complete coverage feature detection for nautical charting of the seafloor and detecting underwater objects with unprecedented precision. This unique combination of DriX and Sams 150 represents a major step forward in the efficiency and accuracy of bathymetric surveys in support of nautical charting.
Unique combination
DriX, a 7.7m-long, highly stable USV, is designed to withstand high-sea conditions. Equipped with a specialized gondola, the USV incorporates advanced sensors, including Sams 150, an MBES and an optional sub-bottom profiler.
Exail’s Sams 150 is an advanced sonar system that combines the operability of traditional sidescan sonar with the enhanced capabilities of synthetic aperture sonar (SAS) technology. It features tight integration with Exail’s Phins inertial navigation system (INS) and other positioning systems to ensure superior motion compensation and deliver georeferenced images by design. The result is consistent, high-resolution sonar imagery, surpassing conventional survey methods in efficiency, coverage and data integrity.
Sams 150’s two processing modes make it highly adaptable to various operational scenarios. These are the SAS mode, for applications requiring centimetric resolution, and the inertial sidescan sonar (inSSS) mode, which utilizes the SAS hardware to extend conventional sidescan processing. This mode is more resilient to platform motion and supports faster data acquisition. The inSSS mode – which was utilized for the operational deployment in the Gulf of Mexico – ensures resilience to motion and enables rapid, high-quality data acquisition.
“A key advantage of this setup is the specially designed gondola, engineered by Exail to seamlessly integrate these advanced sensors (Sams, MBES, INS and option for a sub-bottom profiler) while preserving the DriX’s superior hydrodynamic performance,” explained Olivier Moisan, DriX operations manager. The streamlined gondola design maintains the vehicle’s speed, stability and low fuel consumption. This allows the DriX to operate for extended durations without compromising its efficiency or agility, making it an ideal platform for long-endurance survey missions. “The integration of Sams 150 within the DriX’s gondola – rather than being towed by a vessel – reduces operational complexity and enhances overall survey performance,” added Olivier Moisan.
Demonstrating capabilities in the Gulf of Mexico
The first operational deployment of DriX with Sams 150 took place in the Gulf of Mexico in autumn 2024, validating its performance in real-world conditions. The mission underscored the effectiveness of this next-generation survey solution. Launched and recovered from Cameron, LA, the USV was remotely operated from the Cameron Remote Operation Center (ROC) and from an ROC in Vancouver, WA. The survey covered an impressive 3,729 nautical miles across three designated areas, totalling 861.8 sq km. With its very low fuel consumption, DriX could navigate in supervised autonomy for several days before returning to port. The survey was conducted between six and seven knots, providing an excellent compromise between data quality and operational efficiency.
The survey was carried out using the skunk stripe method in relatively shallow waters (19–23m), where the MBES collected bathymetric data along a near nadir swath while the Sams 150 captured inSSS imagery along the outer edges with a much greater range up to 100m with a line spacing of 180m.
SAMS data was processed using Delph Geo, Exail’s proprietary sonar processing suite. The software provided a real-time waterfall display during acquisition visible from the ROC. In post-processing, Delph Geo enabled efficient batch processing of extensive survey areas, providing gain correction and seamless data merging across multiple survey lines. Despite the challenging conditions in the Gulf of Mexico, with sea states occasionally reaching level four, the software ensured the production of high-quality, motion-compensated sonar imagery.
“The application of the DriX using the combined MBES and Sams 150 systems allowed us to duplicate the production of our larger vessel running MBES and conventional towed sidescan sonar, which required more staff and produced a larger carbon footprint,” explained Jon Dasler, director of Marine Services at DEA. “This helped us meet several of our objectives for the project, which were: to acquire data that met strict NOAA requirements for nautical charting with a lower carbon footprint, to survey in heavier seas than our larger vessel, and to improve the quality of life for our valued hydrographers, enabling them to return home when not on watch in the Vancouver ROC.”
Shaping the future of ocean mapping
NOAA directed this work to support its “Map Once, Use Many Times” initiative, ensuring that the high-quality bathymetric data collected is accessible for a wide range of applications, from nautical charting to scientific research.
The data acquired through this production contract not only supports safe navigation and the flow of maritime commerce but also benefits federal, state and local agencies by providing critical insights for environmental monitoring, coastal management and more. As the technology behind the DriX USV continues to evolve, it is set to play a pivotal role in shaping the future of ocean mapping and maritime operations. By successfully demonstrating the synergy between DriX and Sams 150, this operation paves the way for future deployments in diverse marine environments.
