Farsounder has published an insightful article detailing how it’s Argos series of 3D forward-looking navigation sonars can effectively address the challenges of detecting underwater obstacles in shallow water settings.
For effective navigation in shallow waters, a forward-looking sonar must be capable of detecting from the water’s surface to the seabed, while also providing a broad field of view and rapid update rates.
Initially, unmanned surface vessels (USVs) were deployed in highly controlled environments where the seabed was thoroughly mapped and the underwater conditions were stable. The primary focus of these early USV initiatives was on integrating above-water sensors with the vehicle’s control systems and developing automated path planning. It became evident that navigating through dynamic environments while adhering to COLREGS would be essential for all USV functionalities. By starting in these controlled settings, the complexities of collision avoidance were simplified, allowing for the exclusion of underwater obstacles.
As these initial projects evolved, the applications of USVs quickly transitioned to deeper waters, presenting new challenges associated with operating in more turbulent, open-water conditions and further from shore-based interaction systems. Still, many of these deep-water USV programs managed to sidestep underwater obstacles by avoiding icy regions and maintaining slower speeds to reduce risks from drifting shipping containers or large marine animals.
In recent years, the integration of basic above-water sensor fusion and compliance with COLREGS has been successfully demonstrated, establishing USVs as viable platforms for an increasing array of applications. With this experience, developers and users of USV platforms are now eager to explore more complex operational environments. Additionally, numerous USV platforms are emerging in the market, promising enhanced operational speeds. As missions expand to include long-term coastal monitoring, security patrols in remote ports, force projection in higher latitudes, ship-to-shore navigation, and rapid interdiction, the consideration of underwater navigation hazards is becoming a critical focus for many USV operators.
A common question arises: ‘Why can’t USVs simply rely on electronic nautical charts (ENCs) to navigate around underwater obstacles?’ While digital charts may seem like a straightforward solution,their effectiveness is limited due to the fact that vast portions of the world’s oceans remain poorly mapped or entirely unmapped. According to HSH Prince Albert II of Monaco’s recent announcement at the International Hydrographic Institution (IHO) Assembly regarding the GEBCO world map, only about 25% of the world’s oceans have been mapped (1). Though, this coverage is only at a resolution of 100 meters, which is inadequate for navigation, and much of the data comes from outdated surveys that are prone to significant errors. Globally, less than 10% of the ocean has been charted using modern sonar technology. the United States has mapped approximately 52% of its waters (2), but only about 35% of that has been done using contemporary methods (3). In coastal waters, only around 50% have been mapped worldwide (4). These areas are particularly hazardous for various vessels, including USVs. Moreover, ENCs do not account for transient obstacles such as whales, ice, and containers, which are crucial to avoid as operational speeds increase.
FarSounder’s Argos sonars create real-time 3D forward-looking sonar images ahead of the vessel while also generating a thorough 3D map of its path.
FarSounder’s Argos series of 3D forward-looking navigation sonars have been specifically engineered to tackle the challenges of detecting underwater obstacles in shallow water environments. Depending on the model, Argos sonars can identify obstacles ahead of the vessel with operational ranges varying from 350 meters (over 1,000 feet) to 1,000 meters (over half a nautical mile). All models provide real-time 3D detection of the seabed and in-water targets from the surface down to 85 meters in depth. They also feature FarSounder’s Local History Mapping functionality, which creates a gridded bathymetric survey of the vessel’s entire journey.
The SonaSoft software that operates the argos sonars handles all system processing and includes both a user-amiable graphical interface and a network-based machine interface. The user interface is designed for ease of use, offering straightforward human-in-the-loop capabilities. The display software features a 3D view of both the 3D Forward Looking Sonar (3D FLS) data and Local History Mapping (LHM) data, while the chart view incorporates overlays of 3D FLS, LHM, AIS, and ARPA data.
FarSounder’s user interface software provides both a 3D View and a Chart Overlay View.
The machine interface allows third-party systems (such as vehicle control systems for autonomous and semi-autonomous operations) to access a 3D point cloud of the fully processed sonar data via a standard Ethernet connection. This same network interface enables direct connectivity to the QPS ecosystem through Qinsy for hydrographic survey applications and to various ECDIS products for integrated bridge system applications.
All models of Argos navigation sonars are well-suited for USV applications,with the argos 500 and Argos 1000 typically utilized on LUSV and XLUSV platforms.The latest addition to the series, the Argos 350, has been specifically designed for smaller USV platforms. The Argos 350’s Transducer Module can be configured with a top-mounted connector, facilitating installation via a hoist mechanism.
Regardless of the size of the USV platform, operating in shallow waters, at higher speeds, or with mission-critical payloads necessitates the ability to avoid underwater hazards. By incorporating a 3D forward-looking sonar into the USV sensor suite, operators can safely access a broader range of environments. This capability enhances the flexibility of the USV platform for various applications. Ultimately, expanding capabilities while minimizing risks boosts the overall return on investment (ROI) for both the vehicle and its missions.
