Advanced Navigation recognises that the depths of the ocean remain one of the least explored frontiers on Earth, containing valuable ecosystems and resources that require careful monitoring.
As the demand for underwater exploration grows, particularly for tasks such as infrastructure inspections and environmental assessments, precision navigation becomes increasingly critical. Navigational errors can lead to costly repercussions and, in some cases, irreparable environmental damage.
Underwater exploration continues to expand, with forecasts indicating significant growth in the sector. The marine technology market is projected to increase from $415 million to $620 million by 2026, reflecting a compound annual growth rate (CAGR) of 6.9%. With this expansion, the need for advanced underwater navigation systems has never been more urgent.
Navigating the Challenges of Underwater Exploration
Global Navigation Satellite Systems (GNSS) have long provided accurate navigation on land and in the air. However, these signals do not penetrate water, rendering them ineffective for marine operations. As a result, underwater explorers have relied on alternative navigation tools, but many of these solutions have their own limitations.
Magnetic compasses and gyrocompasses are commonly used, but they are susceptible to inaccuracies due to magnetic interference or performance degradation at high latitudes. Recognizing these challenges, Advanced Navigation developed the Subsonus acoustic compass. This innovative solution blends underwater acoustic positioning with GNSS-based heading from surface vessels, ensuring precise navigation below the waves.
The Subsonus also integrates an Inertial Navigation System (INS), which compensates for drift and provides additional accuracy by measuring acceleration and rotational movements.
Addressing the Need for Accurate Heading
When navigating underwater, heading is the most crucial navigational output. It determines the direction of travel, ensuring that vessels reach their destinations safely. This is especially vital in deep-sea conditions, where landmarks are absent and visibility is often poor.
In the absence of GNSS, Subsonus offers an advanced solution, overcoming the shortcomings of other methods. For example, visual piloting systems rely on cameras and lighting, but they are often bulky, power-intensive, and heavily dependent on favorable visibility. Magnetic compasses are sensitive to interference, and fiber-optic and ring laser gyrocompasses, while highly accurate, can suffer performance degradation at extreme latitudes due to the Earth’s slower rotational velocity—a phenomenon known as secLat degradation.
Subsonus outperforms these traditional methods by combining acoustic positioning and GNSS heading transfer from surface vessels, offering superior accuracy and reliability.
The Subsonus Acoustic Compass
At the heart of the Subsonus system is its ability to leverage acoustic signals to determine both heading and position underwater, down to depths of 1000 meters (3300 feet). By utilizing acoustic heading transfer technology, GNSS heading data from the surface vessel is transmitted to the underwater asset, enabling highly accurate navigation even in the absence of magnetic or gyrocompasses.
In practical terms, the Subsonus setup involves two units: one mounted on the surface vessel and the other on the underwater vehicle. The surface unit acquires heading data via GNSS, while the underwater unit receives this information through bi-directional USBL (ultra-short baseline) acoustic pings. This allows the underwater asset to calculate its own heading based on its relative orientation to the surface vessel.
This system provides several key benefits:
- Acoustic heading transfer: Underwater units can achieve high-accuracy heading without relying on magnetic or gyrocompasses, eliminating susceptibility to magnetic interference.
- Immunity to latitude effects: The Subsonus system is unaffected by secLat degradation, offering consistent performance even in extreme latitudes where traditional gyrocompasses may falter.
- Compact and integrated design: Subsonus is housed in a miniature titanium enclosure with all processing done internally, requiring only a single Ethernet connection for data output. This makes it an ideal solution for both tethered ROVs (Remotely Operated Vehicles) and untethered AUVs (Autonomous Underwater Vehicles).
The Subsonus system integrates several advanced technologies to enhance its navigational capabilities:
- GNSS Compass: The surface unit is connected to Advanced Navigation’s GNSS Compass, utilizing satellite signals to determine position and heading with high precision.
- USBL-squared Configuration: The acoustic compass technology relies on a new USBL2 configuration, where Subsonus units on the surface vessel and underwater vehicle communicate to calculate the underwater asset’s position relative to the surface. This eliminates the need for costly subsea heading solutions, like fiber-optic gyrocompasses.
- Acoustic Data Communication: The system seamlessly encodes ranging and heading data into acoustic signals, ensuring reliable communication without affecting USBL operations.
- Inertial Navigation System: Integrated INS provides precise measurements of roll, pitch, and acceleration, further refining the navigational accuracy of the system.
Transformative Applications for Subsea Operations
Subsonus is designed to meet the diverse needs of underwater exploration and inspection. Its versatility makes it applicable for a wide range of subsea operations, including environmental monitoring, infrastructure maintenance, and offshore energy inspections. The system’s scalability allows for multiple Subsonus units to be deployed simultaneously, with a single surface unit managing an unlimited number of underwater devices.
Subsonus has already demonstrated its value in real-world applications. For instance, JM Robotics successfully integrated the Subsonus system into their HD3 ROV, resulting in improved navigational performance and reduced operational costs.
Subsonus represents a game-changing technology for underwater exploration, offering unmatched accuracy and scalability in a compact and cost-effective package. With its advanced acoustic positioning and INS, Subsonus is poised to revolutionize subsea navigation across a range of industries, enabling safer and more efficient operations in even the most challenging underwater environments.
