By Peter Stewart

Whether surveying seafloor or dredging port sediment, acquiring continuously accurate, high-quality data in underwater conditions has long been a challenge for marine contractors.

Although technology offers immense potential to support these endeavors, the complexity has often posed significant challenges. For years, these advanced systems required a deep level of expertise to implement effectively, largely due to the intricate interplay of various components.

Take, for example, the process of seafloor mapping. This task typically involves an array of equipment such as multibeam sonar, positioning and orientation systems (POS), laser sensors, speed-of-sound devices, and cutting-edge software to process and interpret data. Ensuring these tools operate in perfect harmony is no small feat, yet it is essential for producing the precise, high-quality underwater data that marine operations necessitate.

As James Dunkley, senior manager of hydrographic surveys at Brownsville, Wisconsin-based Michels Corp., a global power, pipeline, energy and infrastructure construction company, notes: “One of the things people in our industry may not realize until they’ve already invested in technology is the time and cost required to install sensors and integrate systems. Too many times, we must sort these things out on our own.”

More recently, there’s been greater emphasis by developers on prioritizing usability and data quality. The solutions are more intuitive and user-friendly, making it easier for professionals, whether on a boat or in an excavator, to effortlessly access and interpret data without needing to grapple with the intricate mechanics of system configurations.

A POS Perspective

The evolution of POS provides some insights into the ease-of-use evolution of undersea technology. Today’s advanced POS-based marine systems are uniquely suited to the requirements of precision marine motion sensing, hydrographic surveying and charting. They can deliver precise position, heading, attitude, heave, and velocity data for a marine vessel and remote sensing equipment. By combining global navigation satellite system (GNSS) data with angular rate and acceleration derived from an inertial measurement unit (IMU), along with GNSS azimuth measurement system heading, these systems offer an accurate 6 degrees of freedom POS.

When combined with multibeam sonar, hydrographers can generate very precise, georeferenced seafloor mapping data. Manufacturers have devoted considerable time helping customers integrate and configure system components at the factory and during commissioning. The key innovations developers have focused on include improving data availability and quality through the deployment of a seamless GNSS solution that integrates sensor calibration and correction technologies with multibeam sonar.

The Port of London project provides one such example of how these integrated solutions support the all-important hydrographic aspects of a project.

 

 

No Limits with Lidar

The Port of London Authority is charged with ensuring navigational safety and port security along the River Thames, a complex survey area with several bridges, considerable river traffic, and other obstructions that block GNSS line of sight.

Tasked with collecting survey data, the Port of London Authority Hydrographic Service equipped its vessel with a GNSS-aided inertial navigation system for georeferencing a multibeam sonar and a lidar sensor.

With a fully integrated solution, the team was able to capture lidar and multibeam sensor data at the same time to map both the structural elements on the underside of a bridge and the underwater view, providing complete, accurate information in areas where the GNSS environment makes it most difficult to do so, but where, conversely, the need for accuracy is at its highest.

In the near future, complete multibeam solutions with more seamless integration of GNSS, inertial, and other technologies such as lidar will make the technology more accessible to a wider audience beyond just expert hydrographic surveyors to construction, environmental monitoring, search and rescue, and more.

The integration of a real-time correction service, such as Trimble CenterPoint RTX, or post-processing techniques as well as sonar technology also helps to deliver more efficient and accurate dredge operations.

 

 

Resolving the Dredge Dilemma

Much like multibeam sensor integrations for hydrographic surveying, the technological advances to support activities such as dredging are also emphasizing ease of use and quality data with simpler setups. For instance, while sonar was once only the realm of large-scale specialized companies, recent advancements have significantly reduced the cost of sonar systems, making them accessible to a broader range of marine construction projects.

When combined with GNSS systems, advanced sonar-driven 3D visualization tools enable operators to have live feedback on a project’s progress. It eliminates all-too-familiar lags in production while waiting for post-survey results. With this combination, operators have immediate confirmation of grade alignment, object placement, or debris clearance, thus driving improved precision and productivity.

The data in the cab are continuously updating to changing conditions as debris is removed while tracking the precise position and heading of dredging/construction equipment operating underwater. An added benefit is that project teams no longer need a diver to verify underwater conditions, greatly improving job site safety and productivity.

For Michels, it’s a development progression that has forever changed the way the company navigates and excavates underwater projects.

Managing Underwater Parameters

One of the first projects in which Michels was able to take advantage of fully integrated systems was the Missouri River Bedrock Removal Project for the U.S. Army Corps of Engineers, Omaha District. The goal of the project was to excavate a minimum of 120,000 cubic yards of material and restore adequate channel parameters to provide safe navigation of river boat traffic on the Missouri River. The area of concern spanned a little over 2 mi.

“We were basically breaking rock underwater and then removing it,” said Dunkley. “These are pretty inhospitable conditions—and many machine and sensor systems would not work in these harsh conditions.”

 

 

The Michels team mounted a 95-ton Cat 395 excavator on a barge that was tugged into the area of work and equipped with sensors to measure everything from pitch and roll to the movement of excavator attachments. A monitor connected to the Trimble Marine Construction real-time positioning system was used to display survey and design information and provide a visual of the equipment as it moved underwater. Data on the monitor included hydrographic surveys of the river bottom and the dredge prism defining the channel that needed to be cleared: all in 3D, plan and profile views. The pre-dredge/construction hydrographic survey data were collected using a multibeam echosounder with an embedded Applanix GNSS-INS.

The positioning data became particularly crucial for navigating and guiding the excavation work safely, accurately, and efficiently according to project specifications and survey. Even when working underwater, the system continued to provide an accurate real-time depiction of the bucket or other attachment locations, the position of the boom and stick, and their relationship to both the hydrographic survey data and the design layers defining the dredge prism/channel that needed clearing.

“The positioning system performed continuously throughout the entire project duration without any downtime caused by issues with the electronics, components or software,” said Dunkley. “That equates to improved efficiency in the field and successful project execution.”

The firm’s technology-enabled solutions have been deployed on multiple projects, including those that require mobilization of amphibious excavation equipment.

The streamlined integration of technologies such as GNSS and multibeam sonar into marine construction and dredge operations is setting a new standard for efficiency and precision. Solutions blending real-time sonar data with advanced machine guidance systems are no longer reserved for niche projects—they are rapidly becoming industry staples. By pairing hydrographic surveys with coordinated equipment workflows, operators can achieve an unmatched level of situational awareness, optimizing every phase of their operation.

Peter Stewart is the director of marine products at Trimble Applanix.