Dolphin-seeking drones may hold key to marine mammal safety
A workboat-based drone could look out for marine mammals or other warm-blooded species in high-risk locations around windfarms, port developments or even seismic survey areas.
It’s well established that explosive noises from pile drivers or survey streamers (which are designed to be percussive) stresses animals and could damage their sensitive echo-location organs.
The problem is that current detection methods have certain shortcomings: “Environmental experts do have acoustic pickup devices - Passive Acoustic Monitoring Systems or PAMS - but many marine mammals shut down vocalisation when hunting and some species such as Brydes whales, for example, tend not to vocalise that often," said Martin Stanley of Ocean Life Survey.
However, they do have a recognisable heat signature which means that they can be spotted from above using a thermal imaging camera, as they regularly come up for air.
Airborne surveys aren’t new and commonly utilise fixed wing aircraft for marine mammal research. “However, we’ve seen that as we approached, dolphins just dived down out of sight,” Stanley told MJ. Further, they are costly to hire “and as an aircraft passes overhead
fairly quickly, marine mammals obscured under cloudy waster could be missed”.
More, drones are far less expensive, create less shadow and acoustic disturbance and have the ability to turn and hover, allowing for detailed investigation. The system developed by Stanley, which has been tested both in the UK and New Zealand, has a 3.5km or 7km range, depending on country-specific regulation and around half an hour’s flight time. Therefore it’s possible to fly it by direct control or pre-plotted track, change the batteries – which takes less than a minute – then fly it out along a different path. This method also allows coastal surveys to be carried out sequentially along the shoreline.
Interestingly, the drone system is a further development of a vessel-based unit – with significant changes as the boat installation was too heavy for this kind of deployment. As a result “it became necessary to find a lightweight, low-power and cost-effective alternative” explained Stanley.
The answer is kitting out a DJI Phantom 4 so that (along with its standard HD video and controller) it has a long-range, 32,136-pixel thermal camera with adjustable focus, mounted on a base that can provide a 180-degree vertical view and a full 360 degrees in the horizontal plane. The camera can ‘see’ up to 600m and provides GPS location alongside temperature readings for background environments and individual objects: all the data is recorded in the onboard computer for later analysis, but there’s also a live infrared image transmission for flights within 250m.
The Phantom 4 provides a capable foundation, allowing for launch and retrieval from practically any location, land or boat and it can operate in wind speeds up to 10m per second. If the signal is lost it will automatically fly back till it’s recovered or return to a predetermined point.
Usefully, while a vessel-mounted system requires a more expensive thermal camera with a long-range zoom, an onboard drone can physically move around a vessel, and therefore can use a less costly version with a shorter zoom range.
It’s worth noting this thermal imaging system isn’t limited to construction and surveys: it may also help fishing vessels reduce by-catch. The sight of drowned dolphins caught in nets is all too common, but the onboard drone could be flown, day or night, to check the area before and during fishing operations. It’s something that could add to the company’s green credentials pointed out Stanley.
The technology has also recently been deployed along NZ’s Waitakere coastline for a trial survey, supported by the Waitakere Ranges with further assistance from Maui & Hector’s Dolphin Defenders and Auckland Regional Parks.
Martin Stanley concluded: “The work we have undertaken in developing and testing the thermal imaging drones, opens the way for them to be used to improve marine mammal protection and study.”
By Stevie Knight
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