Sample depiction of seafloor and bridge pilings via FarSounder Argos 500 3D FLS.

 

By Matthew Zimmerman
CEO
FarSounder Inc.

Autonomy and uncrewed autonomous vehicle (UxV) systems are hot topics across a variety of industries and vehicle types. For example, it is clear that the pace of adoption and development of drone technology in the maritime sector is increasing dramatically. The confluence of greater at-sea broadband connectivity, artificial intelligence (AI)-based vehicle control systems, the limited pool of mariners, and the success of uncrewed systems in the war in Ukraine has created an enormous opportunity for autonomous/uncrewed surface vessel (ASV/USV) platforms.

Now that the utility of USVs, including their value as a force multiplier, has been demonstrated, the industry is ripe for widespread adoption of these vehicles in not only defense applications but also hydrographic survey, search and rescue, environmental monitoring, and (soon) cargo/passenger transport. As more applications come online, there is one key factor that must not be overlooked: What is underwater, ahead of the vessel, in real time?

It is fairly common to use the information captured in electronic navigation charts (ENCs) to generate a vessel route that avoids the shallows and other underwater obstacles shown on an ENC. However, there is a fundamental problem with this approach: It assumes that the chart’s underlying hydrographic survey data are comprehensive and complete. ENCs may be valuable within the primary shipping channels and in popular locations, but only about 50 percent of coastal waters worldwide has been surveyed by modern standards. This means that as USV missions and applications move into remote coastal locations, nautical charts cannot be relied upon to provide accurate information about underwater hazards.

Historically, USV development focused on the use of above-water sensors (such as GPS, AIS, radar and optical/thermal sensors) and ensuring compliance with U.S. Coast Guard Rules of the Road (COLREGS). Testing of initial platforms took place either in well-charted areas or deepwater locations where concerns about underwater hazards could be minimized. Therefore, the limitations of ENCs could be largely ignored.

However, as ASVs/USVs move out of these simplified environments, that is no longer a valid assumption. Given the limited resources of hydrographic offices around the world, it will take a long time to fully survey all areas of interest. Even the U.S. has only mapped about 52 percent of its territorial waters. Seabed 2030, a joint project of GEBCO and The Nippon Foundation, supported by the International Hydrographic Organization and endorsed by the UN, is working to compile a comprehensive map of the seafloor. However, even when including crowdsourced measurements and data from private survey operators, the definitive global map thus far only covers about 26 percent of the seafloor at a maximum resolution of 100 m.

One method by which traditional, crewed vessels overcome charting limitations in littoral waters is by relying on local knowledge and observations from skilled bridge crew. Such capabilities are nonexistent with uncrewed systems, leading to a lack of situational awareness. Also, charts can’t account for transient obstacles, changes to the seafloor caused by seasonal conditions or natural disasters, or GPS-denied environments. These points are particularly salient when one considers the commercial, military, and scientific pushes into the Arctic, where the environment changes daily, and the various coastal regions of conflict where GPS spoofing and jamming are commonplace.

Above-water sensors can’t detect the uncharted rock pinnacle or coral head. They can’t detect debris that has blocked a previously well-charted channel after a hurricane. They are very limited in their ability to detect the keel of an iceberg or bergy bits. Above-water sensors can’t sense the bathymetry in an austere environment. They are very limited in their ability to detect whales, especially since they spend most of the time below the sea surface.

In the case of whale avoidance, navigating around these creatures is not only important for the vessel’s safety, it is critical for marine mammal protection, as ship strike is one of the leading causes of death for the great whales, including the critically endangered North Atlantic right whale.

Fortunately, above-water sensors are not the only tools available to the ASV/USV community. Their underwater complement is 3D forward-looking sonar (3D FLS). Having first entered the commercial maritime market in 2005, 3D FLS is a mature technology that excels at many of the tasks that limit the effectiveness of above-water sensors. When working in conjunction with other traditional navigation sensors, a vehicle’s control system (and/or remote operators) can employ 3D FLS to build a more complete understanding of the navigational environment, including uncharted bottom features, dynamically changing sandbars and transient objects.

FarSounder’s line of Argos sonars is the market leader in 3D FLS, and they have been installed worldwide on a wide range of vessel types. Though FarSounder’s original focus was on midsize crewed vessels, Argos 3D FLS systems have been in use on uncrewed vessels since 2021. Currently, they are deployed on a variety of defense and civilian USVs, from 14 m in length and longer. Depending upon the model, Argos 3D FLS can operate from 350 m (more than 1,100 ft.) to 1,000 m (more than half a nautical mile) ahead of the vessel.

Argos series sonars provide real-time capabilities, build a bathymetric map of everywhere they go, and have the ability to share a map optionally and anonymously across the FarSounder fleet and contribute to Seabed 2030. The sonar’s output can be accessed through a machine interface for vehicle control systems and via a graphical display for human-in-the-loop operators.

The FarSounder team is currently working on designs for new hardware models focused specifically on USVs less than 14 m in length, which will feature lower power, small footprint and lower cost. The team envisions that these expanded options will enable even more USVs to take advantage of 3D FLS technology, facilitating safer navigation across a wider range of vehicle types.

Learn more here.