Autonomous surface vessels (ASVs)
Using autonomous surface vessels (ASVs) – or self-driving boats – for marine monitoring is safer and much more cost-effective than the current crewed vessel method.
Smaller than crewed vessels, ASVs can operate safely in hazardous locations, and at night, and can cover much larger areas, mitigating risks around crew fatigue. In some cases, they can operate independently of large ships.
ASVs can navigate a reef while towing various sensors, undertake shallow water bathymetric (depth) surveys, using cameras, and collect water samples.
They enable AIMS to simultaneously collect a variety of observations – from both air and water – to create a layered marine monitoring system that integrates observations made underwater, from the sea surface, from air and even space.
Deploying a fleet of ASVs to collect the latest information on water temperature and quality, coral cover and threats such as coral bleaching and crown-of-thorns starfish outbreaks will allow us to scale up our monitoring work.
AIMS has tested several different types of ASVs which can be broadly categorised into long-range and short-range.
Long-range ASVs can function out of the line of a sight of an operator, independent of a mothership, for weeks or months at a time, while short-range vehicles are typically deployed for up to one day and controlled (or monitored) by a nearby operator.
AIMS has operated tenders (small vessels) with dive teams specialised in marine monitoring for decades.
In 2020, AIMS had the opportunity to assess an AUV’s capability to collect data when we had access to Marine Advanced Robotics’ WAM-V, a short-range tender-sized ASV, during a four-day field trip at John Brewer Reef, 40 nautical miles from Townsville.
The intent was to determine if this ASV type had potential for routine deployment from AIMS’ ships, and to conduct a series of preliminary dataset collection missions.
The WAM-V was owned by Queensland University of Technology (QUT) which had integrated sophisticated sensors, winches, software and algorithms into the base platform to enable it to autonomously complete tasks.
We conducted experiments with different sensors including sonar, LiDAR (a detection system which works on the principle of radar but uses light from a laser) and imaging devices.
We found the platform to be a viable base for conducting sonar bathymetry surveys and benthic (flora and fauna of the sea floor) imaging, particularly in shallow reef-flat areas and results indicated it could be used for automated imaging and reef mapping during routine surveys.
However, we found at-sea stowage and handling for deployment increased costs and could limit the scalability of deploying this type of ASV for routine observations.
In 2020 we also trialled a smaller more portable platform, a low-cost inflatable vessel – the SurfBee – on John Brewer Reef, in collaboration with QUT.
The SurfBee successfully completed reef flat transects in a ‘mowing-the-lawn’ pattern, producing high resolution images of the sea floor via its camera.
While not designed for reliable use in open oceans, the SurfBee demonstrated that small vessels can collect quality datasets over defined transects.
We found that if deployed in a planned and controlled ‘swarm’, they had potential to be effective tool for rapid reef monitoring.
Long-range ASVs have the potential to conduct reef surveys without large surface ship dependencies and could provide efficiency gains for routine at-sea observations.
In 2017, we trialled the Wave Glider, a long-range ASV powered by waves and the sun, developed by Boeing subsidiary Liquid Robotics.
The first seven-day trial saw the low-speed vehicle cover 200 nautical miles navigating around the reefs of the central Great Barrier Reef. A second trial was held off the coast of north-west Australia.
While the trials were successful and the Wave Glider performed well, AIMS’ focus shifted to short-range ASVs as they offered potential to more efficiently scale our routine monitoring work without radically changing our methodologies and processes.
We concluded that integrating one or two long range ASVs into operations was too big a jump to cost-effectively integrate when AIMS had no prior experience with even short-range ASVs.
ASV trial findings
While dependent on a manned mothership for deployment, a small fleet of ASVs could empower AIMS to cost-effectively collect datasets over larger and more inaccessible areas in a relatively short time.
ASVs can be fitted with multiple instruments, enabling collection of reef images for coral health and classification assessments as well as seawater measurements such as temperature and water quality.