There’s a bad habit in the offshore construction survey industry. It’s a tendency to use the biggest tool in the box to crack even the smallest of nuts. The problem is this can result in the demise of many good ideas as the cost of the tool is too expensive. Now it’s also too emissions heavy.

It’s a problem that hinders progress, but it doesn’t have to be that way. Other sectors that operate in the marine space are now finding new, smaller, smarter, cleaner tools. They’ve been using uncrewed surface vessels (USVs), so the big, crewed vessels can stick to the jobs they’re good at.

USVs are no longer new. They’ve been used in defence for some time now, for a range of tasks from surveillance to mine counter measures. USVs are being used to survey coastal and offshore waters in hydrographic surveys, for ocean science and in oil and gas. They’re being used to go out and gather data, either as a platform for oceanographic instruments or by carrying acoustic communications systems to harvest data from sensors deployed at the seabed. You could think of them being like a remote-controlled Dunker!

USVS: PART OF THE OFFSHORE TOOLKIT

In offshore renewables and oil and gas they’re being used as part of site and seismic surveys, and then through field life, for inspection operations. They’re now also being used for maintenance and repair, by acting as deployment platforms for autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs) and even aerial drones (UAVs). You get the picture; USVs are now part of the toolbox across a number of sectors and the levels of sophistication and capability are increasing.

So why are we not using them heavily in offshore construction? One reason may be because offshore construction was in fact an early adopter. But, at the time, there were only a handful of commercial USV operators whose vehicles were just too big for what was needed, making them unwieldy to deploy from an offshore vessel, defeating the point of the exercise.

It’s a different story today. There’s a wide choice of USVs to pick from, from one-man portable USVs to full sized vessels, from fully electric coastal systems to hybrid long-range ocean-going vehicles that can operate for weeks on end. The range of commercial models has also grown. You can buy them outright or purchase a data service where you just order the end result – be it data or an inspection campaign.  

So, we think that it’s time to re-think where USVs can play a role in construction operations; where can they help reduce reliance on the heavyweight, costly and emissive tools we use today? Where can they help to free-up more costly and/or emissive assets; what tasks do we not need a construction vessel to be on site for?

COMPATT BOX-INS & LBL CALIBRATION 

LBL Array Calibration

An obvious one is Long BaseLine (LBL) calibration, both surface box-ins and baseline data collection. LBL calibrations are generally carried out from a construction vessel using a combination of ROVs or over the side dunker to collect baseline data, then, to carry out box-ins using an over-the-side dunker or the vessel’s Ultra-Short BaseLine (USBL) system.

The problem with this approach is that it ties the construction vessel to the location and makes the LBL calibration a single operational routine. Yet, all we need to do this is a dunker once the Compatts are deployed, so why do we need a construction vessel to do it? We just need our USV remote-controlled Dunker.

Multiple USVs are now available that are fitted with both dunkers and USBL systems, including our mid-range Mini-Ranger 2 USBL system, which has been hugely popular across offshore wind applications, and our Ranger 2 system, which can support work in all water depths. Fitted to a USV, they can do everything a crewed construction vessel can do in terms of data collection, while the construction vessel can go off and get on with other activities, either in the same area or at a different location.

Surface Box-In

Depending on the location and operational scenario – such as how far away the USV will be working from land or a crewed vessel from which it might be controlled – different USVs could be used. At one end of the spectrum, a small electric system that’s easy to winch on and offboard and poses little risk to anything in the marine environment, would be useful for shorter duration nearfield operations. All it requires is a GNSS antennae and a small dunker (e.g. a Mini-ROVNav 6+ transceiver). 

Baseline data collection and calibration can be even further decoupled from the construction vessel’s schedule by using a larger USV that can be deployed from shore. This also means it can be done on a more opportunistic basis. If the construction vessel isn’t due back in field for a few weeks, calibration can be done in between other jobs the USV might have.

LBL ARRAY DEPLOYMENT

An obvious extension to this, which completely decouples the placing and calibration of the LBL array from crewed vessel operations, is to use the USV to deploy the array, i.e. Compatts. Most USV manufacturers have designed concept systems for free-fall deployment of transponders, which used to be an industry standard method for deploying Compatts to the seabed. Today, the current method is typically to place a Compatt on the seabed using an ROV, which requires a construction vessel. But why? Perhaps it’s operator risk?

Could mutual ground be found by combining a USV that can launch specifically designed ROVs whose sole purpose is to guide, place, and release Compatts onto the seabed? These ‘transponder deploying ROVs’ already exist, and so do the capable USVs, so all it needs is to be joined together into a system.

PIPELINE TOUCHDOWN MONITORING

Another scenario, where we often use a crewed vessel simply as a sensor platform, is pipeline touchdown monitoring. Monitoring the touchdown point is necessary to ensure the correct and safe installation of the pipeline. Because the touchdown point is often some distance from the pipelay vessel or barge, it is typically outside of the range of the vessel’s USBL system or outside the reach of the ROV’s tether.

Some creative ideas have been applied to mitigate these challenges, such as using a Gyro USBL mounted on the pipelay vessel’s stinger, to improve USBL performance to reach the point of touchdown. And pipeline in-line structures have utilised full and sparse LBL arrays, installed on the seabed to create gateways in which to track the pipeline as it passes through.

Sometimes though a separate vessel is often used to sit over the top of the touchdown location; deploy an ROV, to track the pipe as it reaches the seabed; and relay the position back to the pipelay vessel. This is expensive. So why not use a USV?

There are a couple of scenarios. If the pipelay vessel’s own ROV is able to reach the touchdown point, a small electric USV with, for example, a Mini-Ranger 2 USBL system could be deployed from the pipelay vessel with a small crane to relay the ROV’s position. Being small and electric makes it easy to handle and recharge.

For where the pipelay vessel’s ROV can’t reach the touchdown point, there’s a new fleet of USVs entering the market that come with an ROV. These are longer endurance USVs that can be operated over the horizon and out of a shore base, so there are no manual handling requirements. Even the ROV piloting can be done remotely, via the USV, all from a shore base. Again, all the USV needs is a USBL system, perhaps Ranger 2 Gyro USBL, if higher accuracy is required.

CHOOSING THE RIGHT TOOLS FOR THE JOB

These are just a few ideas. Armed with the right toolkit, we think there will be more opportunities to reduce how much crewed vessels are needed in the field, to reduce the exposure of your staff to risks, overheads, emissions and cost. What do you think? We’d love to hear your ideas and help you make them happen.

We’ve been supporting USV operations for more than a decade. Our track record of working with uncrewed systems spans across all the main USV providers and every type of vehicle on the market, from small coastal electric systems to full ocean depth vehicles.

For those who just want data, we offer a USV data harvesting service. For those who want to kit out their own systems, we have a full suite of acoustic and inertial navigation and communication systems to ensure efficient project outcomes.

Whether it’s for long-duration ocean monitoring from a Wave Glider or deepwater ROV deployment, tracking and communications, we have everything you need. It’s about using the right tools for the job, not using a hammer to crack a nut. Get in touch to find out how we can help you.

Read more:

Fugro selects Sonardyne for its uncrewed vessel operations 

Ocean Infinity selects Sonardyne for pioneering Armada fleet 

HydroSurv and Sonardyne advance USV operations for offshore wind 

Will uncrewed systems deliver your next ocean data?