By Chris Sundstrom

The drive for efficiency and accuracy in marine, including subsea, operations is often hampered by the challenge of system integration. Each piece of equipment, for example, a sonar or INS, often runs its own unique protocols and configurations. Marrying these varied components into a cohesive, functional system requires significant time and expense.

Over the years, I have seen organizations integrating disparate systems from various manufacturers, struggling with the complex custom engineering and integration issues, with no guarantee they will work together. This can quickly increase costs, lead to inefficiencies and create significant barriers when entering new industries.

Simplifying integration and reducing operational complexity are key motives that empower the technology ecosystem at Advanced Navigation. The ecosystem’s vision is to have everything automatically configured for the customer with one supplier. This allows for compatibility at a much tighter integration level, leading to better performance via a process that is simpler and, thus, more efficient.

USBL²: Filling A Crucial Gap in Subsea

A compelling case on the power of the technology ecosystem can be demonstrated via Advanced Navigation’s Subsonus USBL² technology.

Historically speaking, obtaining crucial underwater data, such as determining a precise heading, has presented challenges to subsea operations. Traditional methods often relied on fiber-optic gyroscopes (FOGs) or magnetic heading devices. FOGs, while highly accurate, are typically expensive, heavy and complex to set up, limiting their application in certain scenarios. By comparison, magnetic heading devices offer lower accuracy, are prone to drift and errors, can be severely affected by magnetic interference from structures, and struggle with accuracy due to degradation at high latitudes.

Consequently, the USBL market itself has long featured a gap between high-end, complex, and expensive systems and less reliable, prone to instability, low-end options. Combined with the complex and costly setup process, users would struggle to get useful data out of these products.

 

 

Subsonus was developed to bridge this gap by offering a high-accuracy positioning sensor that overcomes issues with magnetic interference at high latitudes while being cost-effective. Subsonus provides a unique USBL configuration option called “USBL-squared” (USBL²). The primary difference from traditional configurations, such as classic USBL or inverted USBL, is having a transducer on both the surface vessel and the tracked object.

Each Subsonus unit contains a high-specification INS alongside its hydrophone array and acoustic sounder. The INS provides 6 degrees of freedom (DoF) data: roll, pitch, magnetic and gyroscopic headings, heave, and acceleration. Data from the inertial sensors is fused using Advanced Navigation’s proprietary algorithms.

The hydrophone array is used to measure the speed of sound through water at the transducer head. Acoustic signals exchanged between units are encoded with data and include inherent multipath rejection filters, allowing information sharing beyond simple ping response.

This multi-pronged approach offers a multitude of benefits. By performing USBL calculations at both the tracked object and surface vessel, each Subsonus unit forms part of a single, highly accurate positioning system. Unlike methods requiring FOGs, USBL² resists magnetic interference, has higher noise tolerance than traditional USBL, and avoids degradation at high latitudes. The high sensitivity and fine granularity of angular measurement from the USBL² architecture help overcome difficulties in precise positioning when dealing with acute slant range, such as in shallow-water conditions, and when attached to more dynamic vessels. USBL² measures the speed of sound at each Subsonus transducer, which is then shared between units for greater precision in range approximation. A single surface Subsonus unit can manage an unlimited number of remote Subsonus transducers.

Additionally, Subsonus introduces modern user-friendly upgrades, including a web-browser-based interface and ethernet connection. The result is a solution that improves heading accuracy, reduces complexity and calibration time, and introduces faster integration into vessel designs.

 

 

Subsonus Tag and Hydrus Micro-AUV

Within Advanced Navigation’s technology ecosystem, Subsonus is a critical component working seamlessly with the rest of the company’s subsea product portfolio, including the Subsonus Tag and the Hydrus hovering micro-AUV. Through real-time data fusion, cross-platform interoperability, and effortless integration of new and legacy products, the whole ecosystem allows for compatibility at a much tighter integration level, delivering practical benefits for customers.

The Subsonus Tag is an acoustic positioning transponder that works with the Subsonus USBL² system. Its purpose is to actively respond to a Subsonus unit, allowing its position to be identified and displayed. The tags are small, battery-powered, easy to use, and require no connectors and minimal maintenance. They also feature an electronic paper screen displaying battery life and other user-friendly features. A single surface Subsonus unit can track multiple tags simultaneously, which is particularly useful for maintaining awareness of divers and subsea operational objects.

Hydrus is a hovering micro-AUV designed for cost-effective benthic and habitat monitoring and underwater surveying. Hydrus is distinct because it features a full navigation and positioning suite that includes an INS, DVL, high-resolution camera, USBL positioning, and acoustic communications, all integrated as standard, rather than as aftermarket options.

Hydrus excels at collecting georeferenced high-resolution imagery and 4K video, enabling the post-processing and creation of detailed digital twins. Its minimal logistics footprint allows for deployment by a single person without large support vessels, making it significantly faster and more affordable for data collection below 50 m. Although Hydrus is an end-user product, it is built to take full advantage of the ecosystem to bring down the cost of complexity. It is compatible with the Subsonus, with no need for additional hardware as Hydrus can leverage the existing capabilities of the Subsonus system.

Some Advanced Navigation customers were already using Subsonus Tags for diver tracking before later purchasing Hydrus, which they then tracked using the same Subsonus system. In these cases, Hydrus was able to take on some of the diving crews’ tasks by optimizing subsea surveying and data collection. This shows how easily operations can expand within a single supplier’s tech ecosystem.

 

 

Small-Scale ROV Program

Subsonus’s capabilities have been demonstrated recently with JM Robotics, one of Scandinavia’s largest suppliers of small, robust ROV systems. JM Robotics was in need of an ultracompact, lightweight heading solution for a small ROV. The task was to inspect buried submarine pipelines in challenging shallow-water conditions near busy areas, with difficulties such as magnetic interference from ferrous pipelines, noise from boats, poor visibility, strong currents and underwater obstacles.

Traditional FOGs were too large, heavy and expensive, while magnetometers were unusable due to interference. This particular application also required complex ROV piloting, using 6 DoF of movement, to follow the hidden pipelines and successfully battle currents and avoid various obstacles.

Subsonus was identified as the best solution due to its small size and minimal weight. It provided an “acoustic compass” function, delivering accurate heading without relying on magnetometers or FOGs. The system was integrated with a DVL for acoustic velocity and altitude reference, leading to a straightforward installation and easy connectivity setup for the team.

The result was a success. JM Robotics found that using Subsonus immediately provided the additional navigation functions and accuracy required. ROV piloting was also improved when visibility became difficult, as Subsonus provided continuous position and acoustic heading data regardless of water turbidity.

A Cohesive Solution

The basic task of navigating underwater is complex and compounded by the challenges of integrating disparate systems from various suppliers. The cost and difficulty associated with such integration continues to be a major hurdle for industry. But it doesn’t need to be.

Advanced Navigation’s technology ecosystem can provide performance benefits derived from tighter system coupling, including enhanced navigational certainty, increased resistance to interference, and adaptability. This approach can empower industry leaders to overcome technical and integration hurdles, enabling them to focus on operational goals, access new market opportunities, and position themselves for success.

 

Chris Sundstrom is the subsea product manager at Advanced Navigation.